Prevalence and Distribution of the Trematode-Transmitting Snail Bithynia siamensis in Southern Thailand

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A total of 1,413 Bithynia siamensis snails were collected between October 2021 and October 2022 using handpicking and scooping methods. Among these, 844 were identified as B. s. siamensis and 569 as B. s. goniomphalos . The snail samples were examined for parasitic infections in the laboratory using shedding and crushing methods. Among the 27 sampling sites, snails from 6 sites were infected with various trematode species (infection rate: 4.95%, 70/1,413). Evaluation of the morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of cercariae (belonging to four families). The identified species included Echinochasmus pelecani (family: Echinostomatidae), Echinostoma revolutum (family: Echinostomatidae), Haematoloechus similis (family: Haematoloechidae), Loxogenoides bicolor (family Lecithodendriidae), and Stictodora tridactyla (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively. Bithynia siamensis trematode infection southern Thailand Echinostome cercariae Xiphidiocercariae Parapleurolophocercous cercariae Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Parasitic diseases transmitted by snails pose a formidable global health challenge, disproportionately affecting populations in developing nations across Africa, Asia, and Latin America. These diseases, facilitated by freshwater snails acting as intermediate hosts, can lead to infections impacting various organs, such as the lungs, liver, biliary tract, intestines, brain, and kidneys. The resulting infections may trigger overactive immune responses, leading to severe consequences, including cancer, organ failure, infertility, and mortality (Choi 1984 ; Hering-Hagenbeck and Schuster 1996 ; Miyamoto et al. 2014 ; Serbina 2014 ; Zheng et al. 2017 ). Despite advancements in healthcare, these diseases persistently afflict populations in developing nations at alarming rates. Several published studies have meticulously documented the intricate interplay between specific parasites and their intermediate host snails, highlighting the pivotal role snails play in the complex dynamics of snail-borne parasitic diseases. A comprehensive understanding of the fundamental biology of these diseases and the vectors involved is crucial to comprehending the expanding geographical spread of these debilitating conditions. This review aims to explore the current understanding of snail-borne parasitic diseases, with a particular focus on their global distribution, physical control measures targeting parasite-transmitting snails, and the epidemiology and clinical manifestations associated with these maladies (Sripa et al. 2010 ; Lu et al. 2018 ). Bithyniidae snails, which are prevalent across various regions of Asia and Europe, including Cambodia, China, Germany, Japan, Korea, Laos, Russia, and Thailand (Hering-Hagenbeck and Schuster 1996 ; Guo et al. 2009 ; Miyamoto et al. 2014 ; Serbina 2014 ), serve as intermediate hosts for liver flukes such as Clonorchis sinensis , Opisthorchis felineus , and Opisthorchis viverrini . These infections have been linked to a spectrum of hepatobiliary diseases, including opisthorchiasis, cholangitis, obstructive jaundice, hepatomegaly, cholecystitis, and biliary lithiasis (Harinasuta et al. 1984 ; Osman et al. 1998 ; Mairiang and Mairiang 2003 ; Sripa et al. 2005 , 2007 ; Kulsantiwong et al. 2013 ). Moreover, evidence suggests that opisthorchiasis may predispose individuals to cholangiocarcinoma development (Thamavit et al. 1978 ; Haswell-Elkins et al. 1992 ; Sithithaworn et al. 1994 ; Vatanasapt et al. 2000 ; Watanapa and Watanapa 2002 ; Honjo et al. 2005 ). In Thailand, Bithyniidae snails are classified into three genera: Bithynia , Hydrobioides , and Wattebledia . Among these genera, only Bithynia snails are recognized for their medical significance (Brandt 1974 ). Notably, Bithynia snails are intermediate hosts of O. viverrini , which is contributing significantly to the increasing prevalence of opisthorchiasis in Thailand. Three taxa of Bithynia are implicated in the transmission of this parasite, with distinct species acting as intermediate hosts in different regions of Thailand. The distribution of Bithynia species across the country has been extensively documented across diverse geographical zones. In the northern regions, B. funiculata and B. s. siamensis are prevalent, whereas in the central and southern areas, B. s. siamensis predominates. Conversely, in the northeast, B. s. goniomphalos is the dominant species. Discrimination among these Bithynia species relies heavily on taxonomic keys, primarily focusing on shell morphology, including size, shape, color, surface sculpture, operculum structure, and arrangement patterns of radular teeth. Table 1 shows a detailed examination of the specific characteristics utilized in the classification of these three bithyniid species (Brandt 1974 ; Tropmed Technical Group 1986 ; Chitramvong 1992 ; Kiatsopit et al. 2011 ; Petney et al. 2012 ). Table 1 Some specific characteristics utilized to classify the three bithyniid species found in Thailand. Species Characteristics Bithynia funiculata Bithynia siamensis goniomphalos Bithynia siamensis siamensis Umbilicus funnel-shaped Wide, not funnel shaped Very narrow Carina Very strong Weak or missing Not seen Apex Very slightly eroded Very eroded Slightly eroded Peridium Olive-brown Brownish-olive or reddish-brown Greenish-olive or straw color and glossy Spire Short, conic truncate spire Long conic spire Sharp apex is not eroded Shell size 10.2–14.8 mm in length, 6.8–9.6 mm in width 10.2–14.9 mm in length, 5.6–8.5 mm in width 7.4–11.0 mm in length, 3.0-6.8 mm in width (Tropmed Technical Group 1986 ) While Bithynia snails have primarily drawn attention for their role in transmitting O. viverrini , they may also serve as intermediate hosts for other medically significant trematodes affecting both humans and animals. Therefore, our study aimed to determine the prevalence and distribution of trematode-transmitting Bithynia snails by gathering specimens from five provinces in southern Thailand. This article emphasizes the profound impact of snail-borne parasitic diseases and underscores the urgent need for intervention strategies to mitigate their devastating effects on public health in affected regions. Materials and Methods Snail Collection and Sampling Sites Bithynia snails were collected from rice fields and stagnant water sources in the southern region of Thailand, totaling 27 survey sites in five provinces, namely, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, and Songkhla. The geographic coordinates of the sampling sites were determined using a global positioning system (GPS) device (Garmin PLUS III, Taiwan) based on the WGS84 datum. The snail specimens were collected between October 2021 and October 2022 by handpicking and scooping methods and then kept in aeration tanks and transported to the Parasitology and Medical Malacology Research Unit (PaMaSU) located at the Biology Department, Faculty of Science, Silpakorn University, Nakhon Pathom, Thailand. Identification was performed using shell morphological assessment based on references from Brandt ( 1974 ) and Upatham et al. ( 1983 ). Furthermore, the snails subsequently underwent molecular studies and trematode infection determination. Molecular Subspecies Study of Bithynia siamensis The genomic DNA of collected snails was extracted from the foot tissues of Bithynia snails. The preserved snail tissue was extracted by using a Wizard® Genomic DNA Purification Kit (Promega, USA). Polymerase chain reaction (PCR) was performed by using the cytochrome oxidase subunit 1 ( cox1 ) primer combination LCO1490: 5’- GGT CAA CAA ATC ATA AAG ATA TTG G- 3’ and HCO2198: 5’- TTA ACT TCA GGG TGA CCA AAA AAT CA- 3’ (Folmer et al. 1994 ). Reactions were set up with a volume of 20 µl containing 2 µl of genomic DNA (50–100 ng), 0.5 µl of each primer (10 µM), 13 µl of ddH 2 O, 4 µl of SolisFAST® Master Mix (5 µM) (Solis Biodyne, Estonia). The PCR thermal cycle involved initial denaturation at 94°C for 4 min; 35 cycles of denaturation at 94°C for 1 min, annealing at 60°C for 30 s, and elongation at 72°C for 2 min (Sato et al. 2009 ); and a final elongation step at 72°C for 10 min, after which the products were stored at -20°C. Subsequently, the PCR products were purified and sequenced by Macrogen (Korea). Forward and reverse strands were assembled as consensus sequences by using MEGA XI with ClustalW under the default settings, and a phylogenetic tree was constructed via neighbor-joining analysis based on p-distances with 1,000 bootstrap replicates. Examination of Trematode Infections and Cercarial Study The cercariae were investigated using shedding and crushing methods. These techniques were employed to examine the whether the snails caused trematode infections. The emergent cercariae were observed using both a stereomicroscope and a light microscope. The morphology of the cercariae was described based on this examination, and the assessment took place while the cercariae were alive and either unstained or vitally stained with 0.5% neutral red. Free-swimming cercariae were observed under a dissecting microscope, and sample measurements (average size in micrometers) were taken using an ocular micrometer. These measurements were taken from specimens that had been fixed with 10% formalin. Images of the cercariae were acquired using a differential interference contrast (DIC) microscope (Olympus BX53, Japan). Subsequently, these cercariae were drawn and identified based on their overall characteristics following references such as Schell ( 1970 ), Yamaguti ( 1971 , 1975 ), Ito ( 1980 ), Nasir ( 1984 ), McCarthy ( 1989 ), Faltýnková et al. ( 2007 ), Krailas et al. ( 2011 , 2014 , 2022 ), Veeravechsukij et al. ( 2018 ), Apiraksena et al. ( 2020 ), and Wongpim et al. ( 2023 ). The cercariae were preserved in 95% ethanol for molecular analysis. Cercarial Molecular Characterization: Insights from Genetic Analysis The genomic DNA of preserved cercariae in 95% ethanol was extracted by using PureLink Genomic DNA Kits (Invitrogen, Thermo Fisher Scientific®, USA). Polymerase chain reaction (PCR) was performed using the internal transcribed spacer 2 (ITS2) primer combination ITS2-F (5’-CTT GAA CGC ACA TTG CGG CCA TGG G-3’) and ITS2-R (5’-GCG GGT AAT CAC GTC TGA GCC GAG G-3’) (Sato et al. 2009 ). Reactions were set conducted with a total volume of 40 µl containing 2 µl of genomic DNA (50–100 ng), 2.5 µl of each primer (10 µM), 10 µl of 2X Platinum Direct PCR Universal Master Mix (Invitrogen, Thermo Fisher Scientific®, USA), 4 µl of Platinum GC Enhancer, and 19 µl of nuclease-free water. The PCR thermal cycles were initial denaturation at 94°C for 4 min; 35 cycles of denaturation at 94°C for 1 min, annealing at 60°C for 30 s, and elongation at 72°C for 2 min (Sato et al. 2009 ); and a final elongation step at 72°C for 10 min, followed by storage at -20°C. Subsequently, the PCR products were purified and sequenced using the next-generation sequencing method by Macrogen (Korea). The consensus sequences were aligned by using MEGA XI with ClustalW under the default settings, and a phylogenetic tree was constructed using maximum-likelihood analysis based on p-distances with 1,000 bootstrap replicates. Results Snail Collection Bithynia snails were collected from the water bodies of paddy fields on the water surface. Through systematic surveying and random sampling, 1,413 B. siamensis snails were meticulously collected from 27 distinct sampling sites in five provinces within the southern region of Thailand (Fig. 1 and Table 2 ). Table 2 Locations, number of Bithynia snails, number of infected snails, and cercariae obtained from collected snails; sampling from 5 provinces in southern Thailand (844 B. S. siamensis and 569 B. s. goniomphalos ). Voucher Number Location Coordinates Collected snails (number) Number of infected snails (Infection rate %) Type: Cercariae species Phatthalung Province 1. SUT 0121001 Khuha Sawan, Mueang District 7° 37' 41.8" N 100° 07' 16.1"E B. s. siamensis (105) 0 - 2. SUT 0121002 Lam Pam 1, Mueang District 7° 37' 33.3"N 100° 07' 46.2"E B. s. siamensis (18) 0 - 3. SUT 0121003 Lam Pam 2, Mueang District 7° 38' 18.4"N 100° 08' 55.4"E B. s. siamensis (6) 0 - 4. SUT 0121004 Thale Noi 1, Khuan Khanun District 7° 44' 26.9"N 100° 08' 23.4"E B. s. siamensis (18) 0 - Songkhla Province 5. SUT 0121009 Ban Mai, Ranot District 7° 48' 30.9"N 100° 17' 09"E B. s. siamensis (8) 0 - 6. SUT 0121010 Ranot, Ranot District 7° 46' 06.17"N 100° 18'53.26"E B. s. siamensis (6) 0 - 7. SUT 0121011 Pak Trae, Ranot District 7° 46' 06.2"N 100° 21' 10.2"E B. s. siamensis (37) 0 - 8. SUT 0121012 Ko Yai, Krasae Sin District 7° 34' 36.1"N 100° 17' 27.4"E B. s. siamensis (24) 0 - 9. SUT 0121013 Khlong Ri, Sathing Phra District 7° 31' 27.3"N 100° 24' 23.5"E B. s. siamensis (1) 0 - Nakhon Si Thammarat Province 10. SUT 0121014 Bo Lo 1, Chian Yai District 8° 06' 52.4"N 100° 06' 09.3"E B. s. siamensis (53) 0 - 11. SUT 0122015 Bo Lo 2, Chian Yai District 8° 06' 55"N 100° 06' 12"E B. s. goniomphalos (243) 2 (0.14%) Virgulate xiphidiocercaria: Loxogenoides bicolor B. s. siamensis (36) 0 - 12. SUT 0121017 Thong Lan, Thong Lamchiak, Chian Yai District 8° 08' 08.4"N 100° 07' 48.9"E B. s. siamensis (5) 0 - 13. SUT 0122018 Don Jik 1, Thong Lamchiak, Chian Yai District 8° 08' 48"N 100° 07' 34"E B. s. goniomphalos (12) 0 - B. s. siamensis (41) 0 - 14. SUT 0122019 Don Jik 2, Thong Lamchiak, Chian Yai District 8° 09' 13"N 100° 06' 25"E B. s. siamensis (20) 0 - 15. SUT 0121020 Chian Yai, Chian Yai District 8° 10' 07"N 100° 08' 56.8"E B. s. siamensis (26) 0 - 16. SUT 0121021 Takhanan, Chian Yai District 8° 10' 02.5"N 100° 09' 19.7"E B. s. siamensis (18) 0 - 17. SUT 0121022 Hu Long, Pak Phanang District 8° 17' 06.6"N 100° 10' 00.4"E B. s. siamensis (4) 0 - 18. SUT 0121023 Khlong Krabue, Pak Phanang District 8° 17' 08.3"N 100° 09' 04.5"E B. s. siamensis (16) 0 - Surat Thani Province 19. SUT 0121026 Thakhoei, Tha Chang District 9° 13' 11.5"N 99° 10' 08.15"E B. s. siamensis (2) 0 - 20. SUT 0121027 Lamet 1, Chaiya District 9° 22' 15.6"N 99° 12' 28.8"E B. s. siamensis (80) 0 - 21. SUT 0122028 Lamet 2, Chaiya District 9° 22' 16"N 99° 12' 28"E B. s. goniomphalos (286) 4 (0.28%) Echinostome cercaria: Echinochasmus pelecani 3 (0.21%) Armatae xiphidiocercaria: Haematoloechus similis B. s. siamensis (100) 0 - 22. SUT 0122029 Lamet 3, Chaiya District 9° 22' 53"N 99° 12' 30"E B. s. goniomphalos (17) 0 - B. s. siamensis (112) 0 - 23. SUT 0121030 Thung 1, Chaiya District 9° 23' 23.4"N 99° 12' 31.1"E B. s. siamensis (18) 0 - 24. SUT 0122031 Thung 2, Chaiya District 9° 23' 28"N 99° 12' 32.1"E B. s. goniomphalos (6) 5 (0.35%) Echinostome cercaria: Echinostoma revolutum B. s. siamensis (11) 0 0 Chumphon Province 25. SUT 0122032 Hadpunkrai 1, Mueang District 10° 34' 40"N 99° 10' 06"E B. s. siamensis (52) 42 (2.97%) Echinostome cercaria: Echinochasmus pelecani 6 (0.42%) Virgulate xiphidiocercaria: Loxogenoides bicolor 2 (0.14%) Parapleurolophocercous cercaria: Stictodora tridactyla 26. SUT 0122033 Hadpunkrai 2, Mueang District 10° 34' 39"N 99° 10' 07"E B. s. siamensis (12) 3 (0.21%) Armatae xiphidiocercaria: Haematoloechus similis 27. SUT 0122034 Bang Luk, Mueang District 10° 32' 33"N 99° 10' 35"E B. s. goniomphalos (5) 3 (0.21%) Virgulate xiphidiocercaria: Loxogenoides bicolor B. s. siamensis (15) 0 - Total 1,413 70 (4.95%) The classification of these collected Bithynia snails was based on their shell morphology. This categorization led to the identification of two subspecies: 844 snails were categorized as B. s. siamensis , and an additional 569 snails were recognized as B. s. goniomphalos (Fig. 2). Molecular Subspecies Study of B. siamensis A study was conducted to investigate the molecular subspecies of B. siamensis snails following classification based on shell morphology. The collected Bithynia snails were identified as belonging to two distinct subspecies: B. s. siamensis and B. s. goniomphalos . To construct a phylogenetic tree, the cox1 gene from mitochondria, with a length of approximately 550–630 base pairs, was utilized. This gene sequence was obtained through maximum-likelihood analysis and compared with sequences from B. s. siamensis and B. s. goniomphalos from various regions of Thailand, including the north, northeast, and central regions (Fig. 3 and Table 3 ). Table 3 List of cytochrome c oxidase subunit 1 ( cox1 ) genes used for phylogenetic analysis. Species of gastropod Location Voucher code GenBank accession number Reference Bithynia s. siamensis Bo Lo 1, Chian Yai district, Nakhon Si Thammarat Province SUT 0121014 PP455495 This study Lamet 1, Chaiya district, Surat Thani Province SUT 0121027 PP455496 Ban Mai, Ranot district, Songkhla Province SUT 0121009 PP455497 Central region, Thailand EU195827.1 - Duangprompo et al. ( 2007 ) Northeast region, Thailand KY118670.1 - Kulsantiwong et al. ( 2013 ) KY118671.1 - KY118672.1 - North region, Thailand MW832465.1 BssH198 Bunchom et al. ( 2021 ) MW832466.1 BssH199 MW832467.1 BssH200 Bithynai s. goniomphalos Lamet 2, Chaiya district, Surat Thani Province SUT 0121028 PP455498 This study Thung 2, Chaiya district, Surat Thani Province SUT 0122031 PP455499 Central region, Thailand EU195833.1 - Duangprompo et al. ( 2007 ) Northeast region, Thailand KY118630.1 - Kulsantiwong et al. ( 2013 ) KY118631.1 - KY118632.1 - MN399671.1 - Tantrawatpan et al. ( 2020 ) MN399672.1 - MN399673.1 - MN399673.1(2) - In the resulting phylogenetic tree, B. s. siamensis and B. s. goniomphalos were observed to cluster together but were separated into three distinct clusters (Fig. 3). Cluster 1 included sequences from B. s. siamensis (KY118670.1-KY118672.1; Kulsantiwong et al., 2013 and MW832465.1-MW832467.1; Bunchom et al., 2021 )d s. goniomphalos (KY118630.1-KY118632.1; Kulsantiwong et al., 2013 and MN399671.1-MN399673.1; Tantrawatpan et al., 2020 ) originating from the north and northeast regions of Thailand. These sequences were previously reported and submitted to the National Center of Biotechnology Information (NCBI) and the European Bioinformatics Institute (EMBL-EBI). Cluster 2 consisted of sequences from B. s. goniomphalos (SUT0121028, SUT0122031) and B. s. siamensis (SUT0121014, SUT0121027, SUT0121009) obtained from the southern region of Thailand, as part of the present study. Cluster 3 included sequences from B. s. siamensis (EU195827.1; Duangprompo et al., 2007 )d s. goniomphalos (EU195833.1; Duangprompo et al., 2007 ) originating from Central Thailand. These sequences were previously reported and submitted to the NCBI (refer to Table 3 ). Parasitic Infections of Snail Specimens Parasitic infections were detected in snails collected from 6 of the 27 sampling sites, resulting in a cercarial infection rate of 4.95% (70 out of 1,413). The morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of cercariae (belonging to four families). The identified species include Echinochasmus pelecani Johnston and Simpson, 1944 (family: Echinostomatidae), Echinostoma revolutum (Frölich ( 1802 ) Looss, 1899 (family: Echinostomatidae), Haematoloechus similis Looss, 1899 (family: Haematoloechidae), Loxogenoides bicolor (Krull, 1933 ) Kaw, 1945 (family: Lecithodendriidae), and Stictodora tridactyla Martin and Kuntz, 1955 (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively. Morphology of the Cercariae Analysis of emerging cercariae involved the examination of both live cercariae extracted from collected snails and formalin-fixed cercariae. Using a DIC microscope, images of the cercariae were captured, and their sizes were measured to determine their species. Based on their morphological and organ characteristics, the cercariae were categorized into four types: Echinostome cercariae, Armatae xiphidiocercariae, Virgulate xiphidiocercariae, and Parapleurolophocercous cercariae. The differentiation of these five cercariae is detailed as follows. Type 1. Echinostome cercariae Family: Echinostomatidae (Looss, 1899 ) Poche, 1926 Echinochasmus pelecani Cercariae were detected in 42 B. s. siamensis and 4 B. s. goniomphalos specimens, resulting in an infection rate of 3.26% (46/1,413) relative to the total number of collected snails. The cercarial body displays an enlarged, oval-elongate shape and is clear white in color, without eyespots. The oral sucker is located anteriorly with 3 openings of the duct, while the collar spine remains unobservable. Throughout the entire body, internal organs exhibit a dense distribution of granules and cystogenous glands, impeding clear visualization of the penetration gland and other structures. The pharynx is medium in size, and the esophagus is situated between the pharynx and ventral sucker, bifurcating into two intestinal caeca extending to the bladder. The two main excretory tubes converge before entering the bladder. The genital primordia consist of two masses behind the ventral sucker, and the flame cell pattern has not been determined. The tail is connected to the rear of the body, is the same length as the body and flexible, and does not have a finfold (Fig. 4 and Supplementary File 1). The size range and average size (in micrometers, calculated from 10 cercariae) are detailed below: Body 110–191 µm (avg. 155 µm) × 107–149 µm (avg. 124 µm) Pharynx 12–18 µm (avg. 17 µm) × 11–18 µm (avg. 14 µm) Oral sucker 36–46 µm (avg. 42 µm) × 30–44 µm (avg. 40 µm) Ventral sucker 32–39 µm (avg. 35 µm) × 24–41 µm (avg. 33 µm) Excretory bladder 21–30 µm (avg. 24 µm) × 9–10 µm (avg. 9.8 µm) Tail 92-162 µm (avg. 127 µm) × 19–42 µm (avg. 31 µm) Echinostoma revolutum Cercariae were detected in 5 Bithynia s. goniomphalos snails, resulting in an infection rate of 0.35% (5/1,413) (refer to Table 2 ). These cercariae exhibited an elongated pear shape complemented by a circular oral sucker adorned with collar spines. The prepharynx was short, while the pharynx was relatively large. The esophagus displayed a bifurcation into two intestinal caeca situated between the pharynx and the ventral sucker, extending almost to the posterior end of the body. The relatively large ventral sucker was positioned approximately one-third to three-fourths of the body length from the anterior end. Additionally, four pairs of small penetration glands were observed, while the flame cell pattern remained unidentified. Furthermore, the excretory bladder appeared small and displayed an oval-shaped morphology. The slender tail of the cercariae was longer than the body and did not possess a distinct dorsal finfold. The tip of the tail featured an opening to the excretory duct, which exhibited a Y-shaped structure when viewed in an inverted manner (Fig. 5 and Supplementary File 2). The size range and average size (in micrometers, calculated from 10 cercariae) are detailed below: Body 276–450 µm (avg. 376 µm) × 180–260 µm (avg. 220 µm) Pharynx 15–26 µm (avg. 21 µm) × 15–28 µm (avg. 23 µm) Esophagus 95–164 µm (avg. 136 µm) Oral sucker 54–65 µm (avg. 58 µm) × 48–65 µm (avg. 57 µm) Ventral sucker 65–80 µm (avg. 75 µm) × 58–80 µm (avg. 69 µm) Excretory bladder 48–65 µm (avg. 57 µm) × 14–23 µm (avg. 18 µm) Tail 376–650 µm (avg. 491 µm) × 45–57 µm (avg. 51 µm) Type 2. Armatae xiphidiocercariae Family: Haematoloechidae Odening 1964 Haematoloechus similis Cercariae were detected in 3 specimens of B. s. siamensis and 3 specimens of B. s. goniomphalos . The infection rate among the snails was determined to be 0.42% (6/1,413) (refer to Table 2 ). The cercariae have an ovate body shape with a surface adorned with spines. The stylet, which is elongated and lacks a shoulder, is positioned at the anterior oral sucker. Notably, the virgulate gland is absent. The prepharynx is relatively short, and the pharynx is positioned close to the oral sucker. Development of the esophagus, ceca, and genitalia did not occur. The excretory vesicle adopts a Y-shaped configuration. Throughout the body, scattered granules and cystogenous glands hinder the observation of the penetration glands. The tail commences immediately after the body's end, appearing relatively short and cylindrical, lacking a finfold, and having an obliterated tail tubule. The cercaria surface is wrinkled and adorned with small spines (Fig. 6 and Supplementary File 3). The size range and average size (in micrometers, calculated from 10 cercariae) are detailed below: Body 116–251 µm (avg. 172 µm) × 76–115 µm (avg. 91 µm) Stylet 4–8 µm (avg. 5.6 µm) × 2–4 µm (avg. 2.8 µm) Pharynx 5–14 µm (avg. 8 µm) × 6–17 µm (avg. 11 µm) Oral sucker 29–43 µm (avg. 35 µm) × 26–41 µm (avg. 31 µm) Ventral sucker 24–34 µm (avg. 29 µm)23–32 µm (avg. 26 µm) × Excretory bladder 17–25 µm (avg. 21 µm) × 18–26 µm (avg. 21 µm) Tail 89–144 µm (avg. 104 µm) × 20–37 µm (avg. 27 µm) Type 3. Virgulate xiphidiocercariae Family: Lecithodendriidae (Lühe 1901) sensu Odhner, 1910 Loxogenoides bicolor Cercariae were detected in 6 specimens of B. s. siamensis and 5 specimens of B. s. goniomphalos , resulting in an infection rate of 0.78% (11/1,413) of the total number of collected snails (Table 2 ). These cercariae possess an oval shape with a spiny surface adorned throughout with granules. The oral sucker, which is larger than the ventral sucker, is globular and contains an internal stylet, which is present with shouldering. A large virgular organ is located near the oral sucker. The pharynx is distinct, and neither the esophagus nor the ceca were observed. Three pairs of penetration glands are present, located at approximately two-thirds of the body length; the anterior pairs consist of fine granules, while the two posterior pairs contain relatively coarse, dark granules. A U-shaped excretory bladder is present. The tail of the cercaria is spinose and shorter than the body (Fig. 7 and Supplementary File 4). The size range and average size (in micrometers, calculated from 10 cercariae) are detailed below: Body 72–124 µm (avg. 101 µm) × 52–87 µm (avg. 74 µm) Stylet 8–16 µm (avg. 12 µm) × 3–5 µm (avg. 4 µm) Pharynx 9–10 µm (avg. 9.5 µm) × 6–8 µm (avg. 7 µm) Oral sucker 21–32 µm (avg. 28 µm) × 20–28 µm (avg. 23 µm) Ventral sucker 9–17 µm (avg. 15 µm) × 11–17 µm (avg. 15 µm) Excretory bladder 23–31 µm (avg. 27 µm) × 12–23 µm (avg. 17 µm) Tail 72–109 µm (avg. 93 µm) × 27–34 µm (avg. 29 µm) Type 4 Parapleurolophocercous cercariae Family: Heterophyidae (Leiper, 1909 ) Odhner, 1914 Stictodora tridactyla Cercariae were detected in 2 specimens of B. s. siamensis , resulting in an infection rate of 0.14% (2/1,413) of the total number of collected snails (Table 2 ). The cercarial body exhibits an oval shape, and the cuticle is covered with spines. Additionally, delicate bristles are present laterally on the cuticle. A pair of pigmented eyespots is present. The oral sucker is well developed and globular, while the pharynx is small. Seven pairs of penetration glands are located between the pharynx and the anterior margins of the excretory bladder; the ducts are distinct in the oral sucker area. They pass from the penetration glands to terminate near the anterior end of the body. The cystogenous glands are located laterally from slightly below the eyespots to the posterior end of the body. The excretory bladder is thick-walled and V-shaped. The tail of the cercaria is longer than the body and features both lateral and dorsoventral finfolds on each side (Fig. 8 and Supplementary File 5). The size range and average size (in micrometers, calculated from 10 cercariae) are detailed below: Body 127–256 µm (avg. 184 µm) × 91–120 µm (avg. 101 µm) Eyespots 5–13 µm (avg. 8 µm) × 4–10 µm (avg. 7 µm) Oral sucker 33–47 µm (avg. 39 µm) × 31–37 µm (avg. 35 µm) Excretory bladder 33–72 µm (avg. 53 µm) x 18–43 µm (avg. 27 µm) Tail 396–435 µm (avg. 407 µm) × 29–45 µm (avg. 33 µm) Lateral finfold 139–256 µm (avg. 199 µm) × 12–26 µm (avg. 16 µm) Dorso-ventral finfold 212–256 µm (avg. 236 µm) × 11–32 µm (avg. 22 µm) Cercarial Molecular Characterization: Insights from Genetic Analysis In this study, examination of trematode infections in B. s. siamensis and B. s. goniomphalos revealed three distinct cercarial types. All trematodes were subjected to amplification using ITS2 subsequences of approximately 350–800 base pairs to generate a phylogenetic lineage through maximum likelihood analysis. The resulting sequences were compared with ITS2 sequences from GenBank (refer to Fig. 9 and Table 4 ). Table 4 List of internal transcribed spacer 2 ( ITS2 ) sequences used for phylogenetic analysis. Species of trematode Location Voucher code GenBank accession number Stage of trematode References Echinochasmus pelecani Lamet 2, Chaiya District, Surat Thani Province, Thailand SUT 0122028.3 PP460908 Cercaria This study Echinochasmus japonicus - - KT873310.1 - Besprozvannykh et al. ( 2017 ) KT873311.1 Echinostoma revolutum Thung 2, Chaiya District, Surat Thani Province, Thailand SUT 0122031.1 PP460909 Cercaria This study Indiana , United States of America . - AF067850.1 Adult Sorensen et al. ( 1998 ) Grigorevo, Bulgaria - AY168930.1 - Kostadinova and Gibson ( 2003 ) Loxogenoides bicolor Hadpunkrai 1, Mueang District, Chumphon Province, Thailand SUT 0122032.2 PP460910 Cercaria This study Ban Purakom (Phachi drainage, Mae Klong River system), Suan Phueng District, Ratchaburi Province, Thailand - MH991970.1 Cercaria Veeravechsukij et al. ( 2018 ) Tat Duen waterfall (Yom drainage, Chao Phraya River system), Si Satchanalai District, Sukhothai Province, Thailand - MH991971.1 Angiostrongylus cantonensis - - HQ540551.1 - Liu ( 2010 ) In the resultant phylogenetic tree, the trematodes clustered into three distinct groups that were rooted using the nematode Angiostrongylus cantonensis (HQ540551.1; Liu 2010 ) as an outgroup to ensure notable associations. Clusters 1 and 2 comprised Echinostome cercariae, with Cluster 1 including sequences from Echinochamus japonicus (KT873310.1, KT873311.1; Besprozvannykh et al. 2017 ) and Echinochamus pelecani obtained from B. s. goniomphalos from Lamed 2, Chaiya District, Surat Thani Province, Thailand (SUT0122028.3; this study). Cluster 2 represented Echinostoma revolatum obtained from B. s. goniomphalos from Thung 2, Chaiya District, Surat Thani Province, Thailand (SUT0122031.1; this study), as well as E. revolutum from Indiana, U.S.A. (AF067850.1; Sorensen et al. 1998 ) and from Grigorevo, Bulgaria (AY068930.1; Kostadinova et al. 2003). Cluster 3 represented Xiphidiocercariae, consisting of L. bicolor obtained from B. s. goniomphalos in Bang Luk, Mueang District, Chumphon Province, Thailand (SUT0122032.2; this study), which clustered with L. bicolor from Thailand and was reported to infect Tarebia granifera (MH991970.1, MH 991971.1, MH991985.1; Veeravechsukij et al. 2018 ) with high confidence. Thus, this phylogenetic lineage reveals relationships among the species and distinct cercarial types, confirming morphological distinctions. Discussion Bithynia snails Snails are commonly found in various aquatic habitats across tropical regions, with certain species significantly impacting public health due to their role as intermediate hosts for many parasitic diseases. The presence of certain snail species, such as Bithynia spp., in major water development projects in Southeast Asia can have adverse effects on socioeconomic development, as they may contribute to the spread of snail-borne parasitic diseases. Diseases transmitted by snails, particularly opisthorchiasis and echinostomiasis, are considered significant public health concerns in this region. Bithyniidae snails, which are found across continents and the Indo-Pacific Islands, typically exhibit small sizes ranging from 6.5 to 14.8 mm in length and 3.0 to 9.6 mm in diameter. These snails are characterized by ovate-conoidal shells, often in brownish, corneous, or olive colors, with delicate spiral lines instead of pronounced sculpturing. The aperture of their shells tends to be round or ovate, featuring a calcareous operculum typically possessing a paucispiral nucleus. While the Bithyniidae family encompasses numerous genera and species, only a select few within the genus Bithynia hold medical significance. Within the genus Bithynia, further classification revealed two subgenera: Gabbia and Digoniostoma . The Gabbia subgenus includes species such as Bithynia ( Gabbia ) wykojfi , B. ( G. ) walkeri , and B. ( G .) pygmaea , none of which are medically significant. Conversely, the Digoniostoma subgenus comprises species such as Bithynia ( Digoniostoma ) funiculata , B. ( D. ) siamensis , and B. ( D. ) pulchella , which, except for B. pulchella , are medically important. The morphological characteristics and geographical distribution of B. siamensis , which is classified into two different subspecies, B. s. siamensis and B. s . goniomphalos , are important. The specific characteristics utilized in the classification of B. funiculata , B. s. siamensis , and B. s. goniomphalos are detailed in Table 1 (Tropmed Technical Group 1986 ; Petney et al. 2012 , 2018 ). Although B. s. goniomphalos has been reported throughout the Lower Mekong Basin, this species is predominantly found in northeast Thailand. Here, we present findings on the populations of both subspecies of B. siamensis found in southern Thailand. These snails predominantly inhabit freshwater environments, particularly rice fields, ponds, and irrigation canals. Our study focused on differentiating Bithynia subspecies based on morphological shell characteristics, with molecular analysis for confirmation. Molecular analysis was conducted to confirm the identification of B. s. siamensis and B. s. goniomphalos snails collected from the southern region of Thailand based on their shell morphology and sculptures. The nucleotide sequences of B. s. siamensis and B. s. goniomphalos from this study clustered together with their respective species and were clearly separated from those found in the north, northeast, and central regions of Thailand. According to phylogenetic lineage, the distributions of B. s. siamensis and B. s. goniomphalos underscore the significant role of snail cluster differentiation over species differentiation, given their categorization within the same species ( Bithynia siamensis ) and their closely similar shell morphology. B. s. siamensis typically exhibits a conical shell with a pointed apex and a rounded base, featuring a tightly coiled structure with light greenish-brown coloration and a glossy surface. In contrast, B. s. goniomphalos has a thicker shell with brownish coloration and a matte surface. These subtle differences in shell morphology necessitate the use of cox1 sequences to confirm species categorizations (Duangprompo et al. 2007 ; Kulsantiwong et al. 2013 ; Tantrawatpan et al. 2020 ; Bunchom et al. 2021 ). As a result, the differentiation between B. s. siamensis and B. s. goniomphalos based on shell morphology was validated, with both subspecies clustering with their respective species and showing close relationships to each other. In the present study, we confirmed the presence of both B. s. siamensis and B. s. goniomphalos in the southern region of Thailand. Moreover, both B. s. siamensis and B. s. goniomphalos serve as the first intermediate hosts of trematode infections in the study areas. Parasitic Infections of Bithynia Snails Through subspecies differentiation, we determined the prevalence of trematodes in both B. siamensis subspecies. However, the Bithynia s. goniomphalos subspecies was present only in three provinces (not all five provinces), namely, Nakhon Si Thammarat Province, Surat Thani Province, and Chumphon Province. The prevalence of trematode infections in these provinces was assessed in the present study, in which both Bithynia subspecies were found. Seventeen snails of 569 B. s. goniomphalos were infected with four species of trematodes belonging to three classes of cercariae: Echinostome cercariae, Armatae xiphidiocercariae, and Virgulate xiphidiocercariae. Fifty-three of 844 B. s. siamensis snails were infected with four species of trematodes belonging to four classes of cercariae: Echinostome cercariae, Armatae xiphidiocercariae, Virgulate xiphidiocercariae, and Parapleurolophocercous cercariae. According to previous reports, B. s. goniomphalos has been reported as the first intermediate host of many types of cercariae, including Amphistome cercariae, Cystophorous cercariae, Echinostome cercariae, Furcocercous cercariae, Monostome cercariae, Mutabile cercariae, Parapleurolophocercous cercariae, Pleurolophocercous cercariae, Amartae xiphidiocercariae, and Virgulate xiphidiocercariae, whereas B. s. siamensis has also been reported as an intermediate host of cercarial types, including Amphistome cercariae, Gymnocephalous cercariae, Monostome cercariae, Parapleurolophocercous cercariae, Pleurolophocercous cercariae, Strigea cercariae, and Virgulate xiphidiocercariae (Nithiuthai et al. 2002 ; Sri-Aroon et al. 2005 ; Chontananarth and Wongsawad 2013 ; Kulsantiwong et al. 2015 , 2017 ; Sripa et al. 2016 ; Nguyen et al. 2021 ; Krailas et al. 2022 ). However, many reports have differentiated only the cercarial type and not the species of cercariae. In our study, we differentiated the cercarial species using morphology, organ characteristics, and genetic analysis. Five species of cercariae belonging to four families were identified: (1) the family Echinostomatidae, which consists of E. pelecani and E. revolutum ; (2) the family Haematoloechidae, H. similis ; (3) the family Lecithodendriidae, L. bicolor ; and (4) the family Heterophyidae, S. tridactyla . These cercariae are Echinostoma cercariae, Armatae xiphidiocercariae, Virgulate xiphidiocercariae, and Parapleurolophocercous cercariae. Echinostome cercariae were found to comprise two species belonging to two subfamilies: the first subfamily was Echinochasminae, and the second subfamily was Echinostomatinae. These species were E. pelecani and E. revolutum . E. pelecani was found in Surat Thani Province (SUT 0122028: Lamet 2, Chaiya District) and Chumphon Province (SUT 0122032: Hadpunkrai 1, Mueang District). This trematode has never been reported in the southern part of Thailand or in the Bithynia snail host, but this species has been reported in Melanoides tuberculata in the eastern region of Thailand (Krailas et al. 2014 ). E. pelecani was reported in 42 B. s. siamensis and 4 B. s. goniomphalos snails, with an infection rate of 3.26% (46/1413). This trematode was the most prevalent among the other trematodes in this study. E. pelecani was first isolated from the small intestine of a pelican ( Pelecanus conspicillatus ) at Tailem Bend, Murray River, Australia (Johnston and Simpson 1944 ). Even though the worms were of the Echinostoma cercaria type, the cercaria lost its collar spines. In our study, we differentiated E. pelecani using morphological and internal organ characteristics. The morphological character of the body shape distinguishes the cercaria, which shows an oral sucker with three duct openings. Moreover, we analyzed the genetics of the emerging cercariae collected from Bithynia snails to confirm the results of this study. The definitive host of E. pelecani includes several fish-eating birds and mammals; this parasite primarily affects avian hosts, and its complex life cycle involving snails and other aquatic organisms poses risks to human health. Ingestion of contaminated water or undercooked fish containing infective larvae can lead to human infection, resulting in symptoms such as abdominal pain, diarrhea, and malaise (Toledo and Fried 2005 ). This is crucial for assessing its impact on public health. Furthermore, Echinochasmus infections have been reported worldwide, highlighting the global significance of studying and monitoring these parasites for effective control measures (Chai et al. 2005 ). E. revolutum was also found in Surat Thani Province (SUT 0122031: Thung 2, Chaiya District). In this study, E. revolutum was reported in 5 B. s. goniomphalos snails, with an infection rate of 0.35% (5/1413). This parasite was the first Echinostome species discovered in the intestinal flukes of ducks and described in the literature. Infections primarily affect avian hosts; however, accidental ingestion of infected intermediate hosts by humans or other mammals can lead to intestinal infections, causing symptoms such as abdominal pain, diarrhea, and malnutrition. In veterinary medicine, infections in domestic animals, particularly poultry, can result in economic losses due to decreased productivity and mortality (Chai 2009 ; Fried et al. 2018 ). Furthermore, E. revolutum serves as a model organism for studying host-parasite interactions and the immunology of trematode infections, contributing valuable insights to broader parasitological research. Previous reports have shown that E. revolutum is found worldwide, including in Asia, Europe, Africa, Australia, New Zealand, and the Americas. The second intermediate host was the snail genus Filopaludina , which is popular in Asian food. Eating raw or improperly cooked snails can cause human echinostomiasis. It is likely that since E. pelecani was reported to successfully encyst in fish ( Oryzias latipes , Gambusia affinis ), it can also do so in snails ( Lymnaea lessoni , Ameria spp.) and tadpoles ( Crinia sp.). However, both E. pelecani and E. revolutum exemplify the complexity of trematode parasites and their intricate relationships with various hosts. Their widespread distribution, diverse host range, and implications for both veterinary and human health underscore the importance of continued research into the biology, ecology, and control strategies of this fascinating parasite (Kostadinova and Gibson 2003 ; Chai 2009 ; Fried et al. 2018 ). H. similis is a parasite belonging to the family Haematoloechidae. This species can be distinguished as a Xiphidiocercariae type, presenting a stylet in the oral sucker. The genus Haematoloechus has been reported in all zoogeographical regions and is found in the lungs of various anurans (Kim et al. 1992 ). In this study, H. similis was categorized based on the morphological distinction of cercariae. The stylet is a typical structure of the xiphidiocercariae type. Although at least six subgroups of xiphidiocercariae are known (Schell 1970 ), we described H. similis as belonging to the subgroup of Armatae xiphidiocercariae, where the tail is shorter than the body, the dorsoventral finfold is absent, the virgula organ is not found, and the oral and ventral suckers are of equal size. Armatae xiphidiocercariae have been reported as the trematode present in the family Plagiorchidae and include H. similis (Grabda 1960 ; Faltýnková et al. 2007 ). Many Haematoloechus species have been described in the family Haematoloechidae and are characterized by a typical tail structure with the presence of fin folds, indicating the subgroup of Ornatae xiphidiocercariae, order Plagiorchiiformes Olsen 1974 . Here, we present H. similis , which belongs to the family Haematoloechidae and is characterized by simple-tailed xiphidiocercariae without a finfold and a stylet without shouldering (Yamaguti 1975 ). The cercaria were found in Surat Thani Province (SUT 0122028: Lamet 2, Chaiya District) and Chumphon Province (SUT 0122033: Hadpunkrai 2, Mueang District). They were found in 3 B. s. siamensis and 3 B. s. goniomphalos snails, with an infection rate of 0.42% (6/1413). H. similis has been reported in various regions of Thailand, with the thiarid snail M. tuberculata recorded as the first intermediate host, with an infection rate of 1.46% (468/32,026) (Krailas et al. 2014 ). The other Xiphidiocercariae type, belonging to the subgroup Virgulate xiphidiocercariae, has a virgular organ present in the region of the oral sucker. This virgular organ is used for the storage of mucoid secretions and is thought to provide some protection for the cercaria and aid in attachment to substrate materials (Schell 1970 ). L. bicolor , the most common parasite, has been reported to infect many snail species, such as thiarid snails ( M. tuberculata , T. granifera , Thiara (i.e., Mieniplotia ) scraba , and Stenomelania sp.) (Dechruksa et al. 2007 ; Ukong et al. 2007 ; Krailas et al. 2014 ; Veeravechsukij et al. 2018 ; Apiraksena et al. 2020 ) and pachychilid snails ( Brotia costula , Brotia dautzenbergiana , and Brotia wykoffi ) (Pratumsrikajorn et al. 2017 ). Many previous studies have reported on virgulate cercariae infections in Bithynia snails but did not specify the species of the emerging cercariae (Chontananarth and Wongsawad 2013 ; Kulsantiwong et al. 2015 , 2017 ; Sripa et al. 2016 ; Pitaksakulrat et al. 2022 ). Interestingly, L. bicolor is the most common parasite found in almost all studies; it has a high prevalence in collected snails and is distributed in every water body system. In our study, L. bicolor was detected in 6 specimens of B. s. siamensis and 5 specimens of B. s. goniomphalos , resulting in an infection rate of 0.78% (11/1,413). The cercariae were found in Nakhon Si Thammarat Province (SUT 0122015: Bo Lo 2, Chian Yai District) and Chumphon Province (SUT 0122032: Hadpunkrai 1, Mueang District; SUT 0122034: Bang Luk, Mueang District). This Virgulate xiphidiocercariae is produced by trematodes from the family Lecithodendriidae; we reported another Virgulate xiphidiocercariae, Loxogenes liberum , infecting B. s. siamensis from Chana District, Songkhla Province, in a previous article (Krailas et al. 2022 ). These findings confirm that the Bithynia snail is a common intermediate host of Virgulate xiphidiocercariae. One of the trematodes in the family Heterophyidae, S. tridactyla , a Parapleurolophocercous cercariae type, was reported to occasionally infest brackish water and marine snails, while metacercariae encyst in fish, with the definitive hosts being birds and mammals, including humans. Like other heterophyid trematodes, S. tridactyla can have significant implications for both wildlife and human health. While these parasites primarily infect birds, they can also infect fish species consumed by humans, leading to potential zoonotic infections. The consumption of undercooked or raw fish containing infective larvae can result in human intestinal infections, causing symptoms such as abdominal pain, diarrhea, and nausea (Chai et al. 1988 , 2005 , 2009 ; Elsheikha and Elshazly 2008 ). In our previous study, we reported that S. tridactyla was found in thiarid snails such as M. tuberculata , M. jugicostis , and T. granifera (Ukong et al. 2007 ; Krailas et al. 2014 ; Veeravechsukij et al. 2018 ). In this study, we identified S. tridactyla in Chumphon Province (SUT 0122032: Hadpunkrai 1, Mueang District). This species was detected in 2 B. s. siamensis snails, with an infection rate of 0.14% (2/1413). Likewise, the presence of Parapleurolophocercous cercariae raises concerns due to the potential transmission of other pathogens and contaminants through contaminated water sources. Additionally, the consumption of raw or undercooked fish infected with S. tridactyla metacercariae can lead to human infections with other trematode species, such as the liver flukes O. viverrini and C. sinensis or the intestinal flukes Haplorchis spp. and Metagonimus spp., posing risks to public health. In this study, two provinces did not harbor infected Bithynia snails, but in a previous study, we reported three species of trematodes from Bithynia s. siamensis , namely, Gastrothylax crumenifer , Astiotrema monticellii , and Loxogenes liberum , in Chana District, Songkhla Province (Krailas et al. 2022 ). This confirms that Bithynia snails are important trematode-transmitting snails in the southern region of Thailand. The lack of genetic analysis for the cercariae that were not included (i.e., Haematoloechus similis and Stictodora tridactyla ) in this phylogenetic lineage results from the insufficient number of cercariae for genomic DNA extractions; however, the morphological and internal organ characteristics of the cercariae were clearly identified. Additionally, research on the prevalence and distribution of trematodes and transmitting snails can be useful in medical and veterinary fields. The presence of these parasites in both humans and animals underscores the importance of continued research and vigilance in monitoring and controlling trematode infections to protect human and animal health. Conclusion Bithynia snails are recognized for their medical significance due to their role as intermediate hosts of trematodes. The prevalence and distribution of trematode-transmitting snails, specifically B. siamensis , were studied in southern Thailand. Both B. s. siamensis and B. s. goniomphalos specimens were collected, and cercarial infection analysis was conducted to identify trematodes at the larval stage. The morphological and internal organ characteristics of the cercariae allowed for the categorization of trematodes into five species: E. pelecani , E. revolutum , H. similis , L. bicolor , and S. tridactyla . This research holds potential utility in both medical and veterinary fields. The presence of these parasites in both humans and animals underscores the importance of continued research and vigilance in monitoring and controlling trematode infections to protect human and animal health. Declarations All authors have read and agreed to the final manuscript. Funding The financial support came from the Faculty of Science, grant no. SRIF-JRG-2567-06 , and the Thailand Science Research and Innovation (TSRI) National Science, Research and Innovation Fund (NSRF) (Fiscal Year 2024) , project no. 4691774 . Data Availability Code Availability Authors' Contributions Conceptualization and Experiment Design: DK, TW; Field Work: DK, TW, JK, CJ, PT; Laboratory Work: DK, TW, JK; Data Analysis: DK, TW, JK, NV, WD, SS, KT, MG; Manuscript Preparation: DK, TW, JK, NV, MG Compliance with Ethical Standards The authors of this study affirm that all research methods employed in this investigation strictly adhere to the ethical standards established by national and institutional committees concerning the welfare and utilization of laboratory animals. Prior approval for this study was obtained from the Committee for Animal Scientific Research at Silpakorn University, Thailand, under reference number 20/2565. Competing Interests All the authors declare that there is no conflict of interest. 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version\u003c/p\u003e","description":"","filename":"Figure5E.revolatum.png","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/ba37f1ed5785840457c8ae54.png"},{"id":57900144,"identity":"73ba14b9-7da7-4c32-9912-aa53849f6dc0","added_by":"auto","created_at":"2024-06-07 08:36:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2121939,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version\u003c/p\u003e","description":"","filename":"Figure6H.similis.png","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/7b32173012fe3bb46c005a10.png"},{"id":57899435,"identity":"49f7d101-f5cb-48d7-89cc-84a60daa284f","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1681536,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version\u003c/p\u003e","description":"","filename":"Figure8S.tridactyla.png","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/d5c27ac2c116f4393a52e6b5.png"},{"id":57899432,"identity":"551f6d05-844d-4a1a-9dfa-68c39f065935","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":277674,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version\u003c/p\u003e","description":"","filename":"Figure9treepatrasite.png","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/3bffacf993d4b329943ed3f2.png"},{"id":66096833,"identity":"588f9fce-206f-4702-934b-c76cc70d2291","added_by":"auto","created_at":"2024-10-07 16:10:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11216321,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/05cf883c-2d83-4e47-b582-a0583a5924f9.pdf"},{"id":57899429,"identity":"05df4201-f05d-4477-9311-eba2afb54b34","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":18022,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfile1.docx","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/7227cc6daa1b5ba88e1d5559.docx"},{"id":57899423,"identity":"81ee507a-44ac-44ac-b1b1-36060c11aad0","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":18796,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfile2.docx","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/94a1308d6fdb7502fe6533be.docx"},{"id":57899430,"identity":"22dfb46a-f4cc-4e0e-9003-d33690045240","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":17250,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfile3.docx","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/0bb1af6c025f3ef5715d25b1.docx"},{"id":57899428,"identity":"e883cfd7-6b8e-4ecc-b130-e8d0355af9d0","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":18350,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfile4.docx","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/599177cf8e11cdf9c931bcff.docx"},{"id":57899434,"identity":"7852b673-8737-4683-a975-293076d6f74a","added_by":"auto","created_at":"2024-06-07 08:28:46","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":19533,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfile5.docx","url":"https://assets-eu.researchsquare.com/files/rs-4464091/v1/9d535bb53d516be9286aa82e.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Prevalence and Distribution of the Trematode-Transmitting Snail Bithynia siamensis in Southern Thailand","fulltext":[{"header":"Introduction","content":"\u003cp\u003eParasitic diseases transmitted by snails pose a formidable global health challenge, disproportionately affecting populations in developing nations across Africa, Asia, and Latin America. These diseases, facilitated by freshwater snails acting as intermediate hosts, can lead to infections impacting various organs, such as the lungs, liver, biliary tract, intestines, brain, and kidneys. The resulting infections may trigger overactive immune responses, leading to severe consequences, including cancer, organ failure, infertility, and mortality (Choi \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Hering-Hagenbeck and Schuster \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Miyamoto et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Serbina \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Zheng et al. \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Despite advancements in healthcare, these diseases persistently afflict populations in developing nations at alarming rates.\u003c/p\u003e \u003cp\u003eSeveral published studies have meticulously documented the intricate interplay between specific parasites and their intermediate host snails, highlighting the pivotal role snails play in the complex dynamics of snail-borne parasitic diseases. A comprehensive understanding of the fundamental biology of these diseases and the vectors involved is crucial to comprehending the expanding geographical spread of these debilitating conditions. This review aims to explore the current understanding of snail-borne parasitic diseases, with a particular focus on their global distribution, physical control measures targeting parasite-transmitting snails, and the epidemiology and clinical manifestations associated with these maladies (Sripa et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Lu et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBithyniidae snails, which are prevalent across various regions of Asia and Europe, including Cambodia, China, Germany, Japan, Korea, Laos, Russia, and Thailand (Hering-Hagenbeck and Schuster \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Guo et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Miyamoto et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Serbina \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), serve as intermediate hosts for liver flukes such as \u003cem\u003eClonorchis sinensis\u003c/em\u003e, \u003cem\u003eOpisthorchis felineus\u003c/em\u003e, and \u003cem\u003eOpisthorchis viverrini\u003c/em\u003e. These infections have been linked to a spectrum of hepatobiliary diseases, including opisthorchiasis, cholangitis, obstructive jaundice, hepatomegaly, cholecystitis, and biliary lithiasis (Harinasuta et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Osman et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Mairiang and Mairiang \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Sripa et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2005\u003c/span\u003e, \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Kulsantiwong et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Moreover, evidence suggests that opisthorchiasis may predispose individuals to cholangiocarcinoma development (Thamavit et al. \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Haswell-Elkins et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Sithithaworn et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Vatanasapt et al. \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Watanapa and Watanapa \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Honjo et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn Thailand, Bithyniidae snails are classified into three genera: \u003cem\u003eBithynia\u003c/em\u003e, \u003cem\u003eHydrobioides\u003c/em\u003e, and \u003cem\u003eWattebledia\u003c/em\u003e. Among these genera, only \u003cem\u003eBithynia\u003c/em\u003e snails are recognized for their medical significance (Brandt \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1974\u003c/span\u003e). Notably, \u003cem\u003eBithynia\u003c/em\u003e snails are intermediate hosts of \u003cem\u003eO. viverrini\u003c/em\u003e, which is contributing significantly to the increasing prevalence of opisthorchiasis in Thailand. Three taxa of \u003cem\u003eBithynia\u003c/em\u003e are implicated in the transmission of this parasite, with distinct species acting as intermediate hosts in different regions of Thailand. The distribution of \u003cem\u003eBithynia\u003c/em\u003e species across the country has been extensively documented across diverse geographical zones. In the northern regions, \u003cem\u003eB. funiculata\u003c/em\u003e and \u003cem\u003eB. s. siamensis\u003c/em\u003e are prevalent, whereas in the central and southern areas, \u003cem\u003eB. s. siamensis\u003c/em\u003e predominates. Conversely, in the northeast, \u003cem\u003eB. s. goniomphalos\u003c/em\u003e is the dominant species. Discrimination among these \u003cem\u003eBithynia\u003c/em\u003e species relies heavily on taxonomic keys, primarily focusing on shell morphology, including size, shape, color, surface sculpture, operculum structure, and arrangement patterns of radular teeth. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows a detailed examination of the specific characteristics utilized in the classification of these three bithyniid species (Brandt \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1974\u003c/span\u003e; Tropmed Technical Group \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Chitramvong \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Kiatsopit et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Petney et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSome specific characteristics utilized to classify the three bithyniid species found in Thailand.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies Characteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eBithynia funiculata\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eBithynia siamensis goniomphalos\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eBithynia siamensis siamensis\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUmbilicus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003efunnel-shaped\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWide, not funnel shaped\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eVery narrow\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCarina\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVery strong\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeak or missing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNot seen\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVery slightly eroded\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVery eroded\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSlightly eroded\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeridium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOlive-brown\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBrownish-olive or reddish-brown\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGreenish-olive or straw color and glossy\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpire\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShort, conic truncate spire\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLong conic spire\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSharp apex is not eroded\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShell size\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.2\u0026ndash;14.8 mm in length,\u003c/p\u003e \u003cp\u003e6.8\u0026ndash;9.6 mm in width\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.2\u0026ndash;14.9 mm in length,\u003c/p\u003e \u003cp\u003e5.6\u0026ndash;8.5 mm in width\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.4\u0026ndash;11.0 mm in length,\u003c/p\u003e \u003cp\u003e3.0-6.8 mm in width\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e(Tropmed Technical Group \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e1986\u003c/span\u003e)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWhile \u003cem\u003eBithynia\u003c/em\u003e snails have primarily drawn attention for their role in transmitting \u003cem\u003eO. viverrini\u003c/em\u003e, they may also serve as intermediate hosts for other medically significant trematodes affecting both humans and animals. Therefore, our study aimed to determine the prevalence and distribution of trematode-transmitting \u003cem\u003eBithynia\u003c/em\u003e snails by gathering specimens from five provinces in southern Thailand. This article emphasizes the profound impact of snail-borne parasitic diseases and underscores the urgent need for intervention strategies to mitigate their devastating effects on public health in affected regions.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSnail Collection and Sampling Sites\u003c/h2\u003e \u003cp\u003e \u003cem\u003eBithynia\u003c/em\u003e snails were collected from rice fields and stagnant water sources in the southern region of Thailand, totaling 27 survey sites in five provinces, namely, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, and Songkhla. The geographic coordinates of the sampling sites were determined using a global positioning system (GPS) device (Garmin PLUS III, Taiwan) based on the WGS84 datum. The snail specimens were collected between October 2021 and October 2022 by handpicking and scooping methods and then kept in aeration tanks and transported to the Parasitology and Medical Malacology Research Unit (PaMaSU) located at the Biology Department, Faculty of Science, Silpakorn University, Nakhon Pathom, Thailand. Identification was performed using shell morphological assessment based on references from Brandt (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1974\u003c/span\u003e) and Upatham et al. (\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). Furthermore, the snails subsequently underwent molecular studies and trematode infection determination.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eMolecular Subspecies Study of Bithynia siamensis\u003c/h2\u003e \u003cp\u003eThe genomic DNA of collected snails was extracted from the foot tissues of \u003cem\u003eBithynia\u003c/em\u003e snails. The preserved snail tissue was extracted by using a Wizard\u0026reg; Genomic DNA Purification Kit (Promega, USA). Polymerase chain reaction (PCR) was performed by using the cytochrome oxidase subunit 1 (\u003cem\u003ecox1\u003c/em\u003e) primer combination LCO1490: 5\u0026rsquo;- GGT CAA CAA ATC ATA AAG ATA TTG G- 3\u0026rsquo; and HCO2198: 5\u0026rsquo;- TTA ACT TCA GGG TGA CCA AAA AAT CA- 3\u0026rsquo; (Folmer et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Reactions were set up with a volume of 20 \u0026micro;l containing 2 \u0026micro;l of genomic DNA (50\u0026ndash;100 ng), 0.5 \u0026micro;l of each primer (10 \u0026micro;M), 13 \u0026micro;l of ddH\u003csub\u003e2\u003c/sub\u003eO, 4 \u0026micro;l of SolisFAST\u0026reg; Master Mix (5 \u0026micro;M) (Solis Biodyne, Estonia). The PCR thermal cycle involved initial denaturation at 94\u0026deg;C for 4 min; 35 cycles of denaturation at 94\u0026deg;C for 1 min, annealing at 60\u0026deg;C for 30 s, and elongation at 72\u0026deg;C for 2 min (Sato et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2009\u003c/span\u003e); and a final elongation step at 72\u0026deg;C for 10 min, after which the products were stored at -20\u0026deg;C. Subsequently, the PCR products were purified and sequenced by Macrogen (Korea). Forward and reverse strands were assembled as consensus sequences by using MEGA XI with ClustalW under the default settings, and a phylogenetic tree was constructed via neighbor-joining analysis based on p-distances with 1,000 bootstrap replicates.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eExamination of Trematode Infections and Cercarial Study\u003c/h2\u003e \u003cp\u003eThe cercariae were investigated using shedding and crushing methods. These techniques were employed to examine the whether the snails caused trematode infections. The emergent cercariae were observed using both a stereomicroscope and a light microscope. The morphology of the cercariae was described based on this examination, and the assessment took place while the cercariae were alive and either unstained or vitally stained with 0.5% neutral red. Free-swimming cercariae were observed under a dissecting microscope, and sample measurements (average size in micrometers) were taken using an ocular micrometer. These measurements were taken from specimens that had been fixed with 10% formalin. Images of the cercariae were acquired using a differential interference contrast (DIC) microscope (Olympus BX53, Japan). Subsequently, these cercariae were drawn and identified based on their overall characteristics following references such as Schell (\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1970\u003c/span\u003e), Yamaguti (\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e1971\u003c/span\u003e, \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e1975\u003c/span\u003e), Ito (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1980\u003c/span\u003e), Nasir (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1984\u003c/span\u003e), McCarthy (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1989\u003c/span\u003e), Falt\u0026yacute;nkov\u0026aacute; et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), Krailas et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2011\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2014\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), Veeravechsukij et al. (\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), Apiraksena et al. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and Wongpim et al. (\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The cercariae were preserved in 95% ethanol for molecular analysis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eCercarial Molecular Characterization: Insights from Genetic Analysis\u003c/h2\u003e \u003cp\u003eThe genomic DNA of preserved cercariae in 95% ethanol was extracted by using PureLink Genomic DNA Kits (Invitrogen, Thermo Fisher Scientific\u0026reg;, USA). Polymerase chain reaction (PCR) was performed using the internal transcribed spacer 2 (ITS2) primer combination ITS2-F (5\u0026rsquo;-CTT GAA CGC ACA TTG CGG CCA TGG G-3\u0026rsquo;) and ITS2-R (5\u0026rsquo;-GCG GGT AAT CAC GTC TGA GCC GAG G-3\u0026rsquo;) (Sato et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Reactions were set conducted with a total volume of 40 \u0026micro;l containing 2 \u0026micro;l of genomic DNA (50\u0026ndash;100 ng), 2.5 \u0026micro;l of each primer (10 \u0026micro;M), 10 \u0026micro;l of 2X Platinum Direct PCR Universal Master Mix (Invitrogen, Thermo Fisher Scientific\u0026reg;, USA), 4 \u0026micro;l of Platinum GC Enhancer, and 19 \u0026micro;l of nuclease-free water. The PCR thermal cycles were initial denaturation at 94\u0026deg;C for 4 min; 35 cycles of denaturation at 94\u0026deg;C for 1 min, annealing at 60\u0026deg;C for 30 s, and elongation at 72\u0026deg;C for 2 min (Sato et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2009\u003c/span\u003e); and a final elongation step at 72\u0026deg;C for 10 min, followed by storage at -20\u0026deg;C. Subsequently, the PCR products were purified and sequenced using the next-generation sequencing method by Macrogen (Korea). The consensus sequences were aligned by using MEGA XI with ClustalW under the default settings, and a phylogenetic tree was constructed using maximum-likelihood analysis based on p-distances with 1,000 bootstrap replicates.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eSnail Collection\u003c/h2\u003e \u003cp\u003e \u003cem\u003eBithynia\u003c/em\u003e snails were collected from the water bodies of paddy fields on the water surface. Through systematic surveying and random sampling, 1,413 \u003cem\u003eB. siamensis\u003c/em\u003e snails were meticulously collected from 27 distinct sampling sites in five provinces within the southern region of Thailand (Fig.\u0026nbsp;1 and Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLocations, number of \u003cem\u003eBithynia\u003c/em\u003e snails, number of infected snails, and cercariae obtained from collected snails; sampling from 5 provinces in southern Thailand (844 \u003cem\u003eB. S. siamensis\u003c/em\u003e and 569 \u003cem\u003eB. s. goniomphalos\u003c/em\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVoucher Number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCoordinates\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCollected snails (number)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNumber of infected snails\u003c/p\u003e \u003cp\u003e(Infection rate %)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eType: Cercariae species\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003ePhatthalung Province\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1. SUT 0121001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKhuha Sawan, Mueang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 37' 41.8\" N\u003c/p\u003e \u003cp\u003e100\u0026deg; 07' 16.1\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (105)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2. SUT 0121002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLam Pam 1, Mueang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 37' 33.3\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 07' 46.2\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3. SUT 0121003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLam Pam 2, Mueang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 38' 18.4\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 08' 55.4\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4. SUT 0121004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThale Noi 1, Khuan Khanun District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 44' 26.9\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 08' 23.4\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eSongkhla Province\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5. SUT 0121009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBan Mai, Ranot District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 48' 30.9\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 17' 09\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6. SUT 0121010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRanot, Ranot District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 46' 06.17\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 18'53.26\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7. SUT 0121011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePak Trae, Ranot District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 46' 06.2\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 21' 10.2\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (37)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8. SUT 0121012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKo Yai, Krasae Sin District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 34' 36.1\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 17' 27.4\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9. SUT 0121013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKhlong Ri, Sathing Phra District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026deg; 31' 27.3\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 24' 23.5\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eNakhon Si Thammarat Province\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10. SUT 0121014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBo Lo 1, Chian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 06' 52.4\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 06' 09.3\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e11. SUT 0122015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBo Lo 2, Chian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e8\u0026deg; 06' 55\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 06' 12\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. goniomphalos\u003c/em\u003e (243)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 (0.14%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eVirgulate xiphidiocercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eLoxogenoides bicolor\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12. SUT 0121017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThong Lan, Thong Lamchiak,\u003c/p\u003e \u003cp\u003eChian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 08' 08.4\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 07' 48.9\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e13. SUT 0122018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDon Jik 1, Thong Lamchiak,\u003c/p\u003e \u003cp\u003eChian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e8\u0026deg; 08' 48\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 07' 34\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. goniomphalos\u003c/em\u003e (12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (41)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14. SUT 0122019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDon Jik 2, Thong Lamchiak,\u003c/p\u003e \u003cp\u003eChian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 09' 13\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 06' 25\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (20)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15. SUT 0121020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChian Yai, Chian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 10' 07\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 08' 56.8\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (26)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16. SUT 0121021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTakhanan, Chian Yai District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 10' 02.5\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 09' 19.7\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e17. SUT 0121022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHu Long, Pak Phanang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 17' 06.6\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 10' 00.4\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e18. SUT 0121023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKhlong Krabue,\u003c/p\u003e \u003cp\u003ePak Phanang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u0026deg; 17' 08.3\"N\u003c/p\u003e \u003cp\u003e100\u0026deg; 09' 04.5\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (16)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eSurat Thani Province\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e19. SUT 0121026\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThakhoei, Tha Chang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u0026deg; 13' 11.5\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 10' 08.15\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20. SUT 0121027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLamet 1, Chaiya District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u0026deg; 22' 15.6\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 12' 28.8\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (80)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e21. SUT 0122028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eLamet 2, Chaiya District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e9\u0026deg; 22' 16\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 12' 28\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eB. s. goniomphalos\u003c/em\u003e (286)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4 (0.28%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEchinostome cercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eEchinochasmus pelecani\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (0.21%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eArmatae xiphidiocercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eHaematoloechus similis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22. SUT 0122029\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLamet 3, Chaiya District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e9\u0026deg; 22' 53\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 12' 30\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. goniomphalos\u003c/em\u003e (17)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (112)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23. SUT 0121030\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThung 1, Chaiya District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u0026deg; 23' 23.4\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 12' 31.1\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e24. SUT 0122031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eThung 2, Chaiya District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e9\u0026deg; 23' 28\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 12' 32.1\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. goniomphalos\u003c/em\u003e (6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5 (0.35%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEchinostome cercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eEchinostoma revolutum\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eChumphon Province\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e25. SUT 0122032\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eHadpunkrai 1, Mueang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e10\u0026deg; 34' 40\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 10' 06\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e42 (2.97%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEchinostome cercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eEchinochasmus pelecani\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6 (0.42%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eVirgulate xiphidiocercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eLoxogenoides bicolor\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 (0.14%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eParapleurolophocercous cercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eStictodora tridactyla\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26. SUT 0122033\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHadpunkrai 2, Mueang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u0026deg; 34' 39\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 10' 07\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (0.21%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eArmatae xiphidiocercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eHaematoloechus similis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e27. SUT 0122034\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBang Luk, Mueang District\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e10\u0026deg; 32' 33\"N\u003c/p\u003e \u003cp\u003e99\u0026deg; 10' 35\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. goniomphalos\u003c/em\u003e (5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (0.21%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eVirgulate xiphidiocercaria:\u003c/p\u003e \u003cp\u003e\u003cem\u003eLoxogenoides bicolor\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eB. s. siamensis\u003c/em\u003e (15)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTotal 1,413\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e70 (4.95%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe classification of these collected \u003cem\u003eBithynia\u003c/em\u003e snails was based on their shell morphology. This categorization led to the identification of two subspecies: 844 snails were categorized as \u003cem\u003eB. s. siamensis\u003c/em\u003e, and an additional 569 snails were recognized as \u003cem\u003eB. s. goniomphalos\u003c/em\u003e (Fig.\u0026nbsp;2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eMolecular Subspecies Study of B. siamensis\u003c/h2\u003e \u003cp\u003eA study was conducted to investigate the molecular subspecies of \u003cem\u003eB. siamensis\u003c/em\u003e snails following classification based on shell morphology. The collected Bithynia snails were identified as belonging to two distinct subspecies: \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e. To construct a phylogenetic tree, the \u003cem\u003ecox1\u003c/em\u003e gene from mitochondria, with a length of approximately 550\u0026ndash;630 base pairs, was utilized. This gene sequence was obtained through maximum-likelihood analysis and compared with sequences from \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e from various regions of Thailand, including the north, northeast, and central regions (Fig.\u0026nbsp;3 and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eList of cytochrome c oxidase subunit 1 (\u003cem\u003ecox1\u003c/em\u003e) genes used for phylogenetic analysis.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies of gastropod\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVoucher code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGenBank accession number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"9\" rowspan=\"10\"\u003e \u003cp\u003e\u003cem\u003eBithynia s. siamensis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBo Lo 1, Chian Yai district, Nakhon Si Thammarat Province\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0121014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP455495\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eThis study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLamet 1, Chaiya district, Surat Thani Province\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0121027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP455496\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBan Mai, Ranot district, Songkhla Province\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0121009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP455497\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCentral region, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEU195827.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDuangprompo et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eNortheast region, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKY118670.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eKulsantiwong et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKY118671.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKY118672.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eNorth region, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMW832465.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBssH198\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eBunchom et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMW832466.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBssH199\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMW832467.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBssH200\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"9\" rowspan=\"10\"\u003e \u003cp\u003e\u003cem\u003eBithynai s. goniomphalos\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLamet 2, Chaiya district, Surat Thani Province\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0121028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP455498\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eThis study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThung 2, Chaiya district, Surat Thani Province\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0122031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP455499\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCentral region, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEU195833.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDuangprompo et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"6\" rowspan=\"7\"\u003e \u003cp\u003eNortheast region, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKY118630.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eKulsantiwong et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKY118631.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKY118632.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMN399671.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eTantrawatpan et al. (\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMN399672.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMN399673.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMN399673.1(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn the resulting phylogenetic tree, \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e were observed to cluster together but were separated into three distinct clusters (Fig.\u0026nbsp;3).\u003c/p\u003e \u003cp\u003eCluster 1 included sequences from \u003cem\u003eB. s. siamensis\u003c/em\u003e (KY118670.1-KY118672.1; Kulsantiwong et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e and MW832465.1-MW832467.1; Bunchom et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e)d s. \u003cem\u003egoniomphalos\u003c/em\u003e (KY118630.1-KY118632.1; Kulsantiwong et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e and MN399671.1-MN399673.1; Tantrawatpan et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) originating from the north and northeast regions of Thailand. These sequences were previously reported and submitted to the National Center of Biotechnology Information (NCBI) and the European Bioinformatics Institute (EMBL-EBI). Cluster 2 consisted of sequences from \u003cem\u003eB. s. goniomphalos\u003c/em\u003e (SUT0121028, SUT0122031) and \u003cem\u003eB. s. siamensis\u003c/em\u003e (SUT0121014, SUT0121027, SUT0121009) obtained from the southern region of Thailand, as part of the present study. Cluster 3 included sequences from \u003cem\u003eB. s. siamensis\u003c/em\u003e (EU195827.1; Duangprompo et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e)d s. \u003cem\u003egoniomphalos\u003c/em\u003e (EU195833.1; Duangprompo et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) originating from Central Thailand. These sequences were previously reported and submitted to the NCBI (refer to Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003eParasitic Infections of Snail Specimens\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eParasitic infections were detected in snails collected from 6 of the 27 sampling sites, resulting in a cercarial infection rate of 4.95% (70 out of 1,413). The morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of cercariae (belonging to four families). The identified species include \u003cem\u003eEchinochasmus pelecani\u003c/em\u003e Johnston and Simpson, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1944\u003c/span\u003e (family: Echinostomatidae), \u003cem\u003eEchinostoma revolutum\u003c/em\u003e (Fr\u0026ouml;lich (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1802\u003c/span\u003e) Looss, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1899\u003c/span\u003e (family: Echinostomatidae), \u003cem\u003eHaematoloechus similis\u003c/em\u003e Looss, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1899\u003c/span\u003e (family: Haematoloechidae), \u003cem\u003eLoxogenoides bicolor\u003c/em\u003e (Krull, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1933\u003c/span\u003e) Kaw, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1945\u003c/span\u003e (family: Lecithodendriidae), and \u003cem\u003eStictodora tridactyla\u003c/em\u003e Martin and Kuntz, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1955\u003c/span\u003e (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eMorphology of the Cercariae\u003c/h2\u003e \u003cp\u003eAnalysis of emerging cercariae involved the examination of both live cercariae extracted from collected snails and formalin-fixed cercariae. Using a DIC microscope, images of the cercariae were captured, and their sizes were measured to determine their species. Based on their morphological and organ characteristics, the cercariae were categorized into four types: Echinostome cercariae, Armatae xiphidiocercariae, Virgulate xiphidiocercariae, and Parapleurolophocercous cercariae. The differentiation of these five cercariae is detailed as follows.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eType 1. Echinostome cercariae\u003c/h2\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003eFamily: Echinostomatidae (Looss, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1899\u003c/span\u003e) Poche, 1926\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section4\"\u003e \u003ch2\u003eEchinochasmus pelecani\u003c/h2\u003e \u003cp\u003eCercariae were detected in 42 \u003cem\u003eB. s. siamensis\u003c/em\u003e and 4 \u003cem\u003eB. s. goniomphalos\u003c/em\u003e specimens, resulting in an infection rate of 3.26% (46/1,413) relative to the total number of collected snails. The cercarial body displays an enlarged, oval-elongate shape and is clear white in color, without eyespots. The oral sucker is located anteriorly with 3 openings of the duct, while the collar spine remains unobservable. Throughout the entire body, internal organs exhibit a dense distribution of granules and cystogenous glands, impeding clear visualization of the penetration gland and other structures. The pharynx is medium in size, and the esophagus is situated between the pharynx and ventral sucker, bifurcating into two intestinal caeca extending to the bladder. The two main excretory tubes converge before entering the bladder. The genital primordia consist of two masses behind the ventral sucker, and the flame cell pattern has not been determined. The tail is connected to the rear of the body, is the same length as the body and flexible, and does not have a finfold (Fig.\u0026nbsp;4 and Supplementary File 1).\u003c/p\u003e \u003cp\u003eThe size range and average size (in micrometers, calculated from 10 cercariae) are detailed below:\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e110\u0026ndash;191 \u0026micro;m (avg. 155 \u0026micro;m) \u0026times; 107\u0026ndash;149 \u0026micro;m (avg. 124 \u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePharynx\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12\u0026ndash;18 \u0026micro;m (avg. 17 \u0026micro;m) \u0026times; 11\u0026ndash;18 \u0026micro;m (avg. 14 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36\u0026ndash;46 \u0026micro;m (avg. 42 \u0026micro;m) \u0026times; 30\u0026ndash;44 \u0026micro;m (avg. 40 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVentral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32\u0026ndash;39 \u0026micro;m (avg. 35 \u0026micro;m) \u0026times; 24\u0026ndash;41 \u0026micro;m (avg. 33 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExcretory bladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21\u0026ndash;30 \u0026micro;m (avg. 24 \u0026micro;m) \u0026times; 9\u0026ndash;10 \u0026micro;m (avg. 9.8 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTail\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e92-162 \u0026micro;m (avg. 127 \u0026micro;m) \u0026times; 19\u0026ndash;42 \u0026micro;m (avg. 31 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eEchinostoma revolutum\u003c/h2\u003e \u003cp\u003eCercariae were detected in 5 \u003cem\u003eBithynia s. goniomphalos\u003c/em\u003e snails, resulting in an infection rate of 0.35% (5/1,413) (refer to Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). These cercariae exhibited an elongated pear shape complemented by a circular oral sucker adorned with collar spines. The prepharynx was short, while the pharynx was relatively large. The esophagus displayed a bifurcation into two intestinal caeca situated between the pharynx and the ventral sucker, extending almost to the posterior end of the body. The relatively large ventral sucker was positioned approximately one-third to three-fourths of the body length from the anterior end. Additionally, four pairs of small penetration glands were observed, while the flame cell pattern remained unidentified. Furthermore, the excretory bladder appeared small and displayed an oval-shaped morphology. The slender tail of the cercariae was longer than the body and did not possess a distinct dorsal finfold. The tip of the tail featured an opening to the excretory duct, which exhibited a Y-shaped structure when viewed in an inverted manner (Fig.\u0026nbsp;5 and Supplementary File 2).\u003c/p\u003e \u003cp\u003eThe size range and average size (in micrometers, calculated from 10 cercariae) are detailed below:\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e276\u0026ndash;450 \u0026micro;m (avg. 376 \u0026micro;m) \u0026times; 180\u0026ndash;260 \u0026micro;m (avg. 220 \u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePharynx\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u0026ndash;26 \u0026micro;m (avg. 21 \u0026micro;m) \u0026times; 15\u0026ndash;28 \u0026micro;m (avg. 23 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEsophagus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e95\u0026ndash;164 \u0026micro;m (avg. 136 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54\u0026ndash;65 \u0026micro;m (avg. 58 \u0026micro;m) \u0026times; 48\u0026ndash;65 \u0026micro;m (avg. 57 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVentral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e65\u0026ndash;80 \u0026micro;m (avg. 75 \u0026micro;m) \u0026times; 58\u0026ndash;80 \u0026micro;m (avg. 69 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExcretory bladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48\u0026ndash;65 \u0026micro;m (avg. 57 \u0026micro;m) \u0026times; 14\u0026ndash;23 \u0026micro;m (avg. 18 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTail\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e376\u0026ndash;650 \u0026micro;m (avg. 491 \u0026micro;m) \u0026times; 45\u0026ndash;57 \u0026micro;m (avg. 51 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eType 2. Armatae xiphidiocercariae\u003c/h2\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003eFamily: Haematoloechidae Odening \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e1964\u003c/span\u003e\u003c/h2\u003e \u003cdiv id=\"Sec18\" class=\"Section4\"\u003e \u003ch2\u003eHaematoloechus similis\u003c/h2\u003e \u003cp\u003eCercariae were detected in 3 specimens of \u003cem\u003eB. s. siamensis\u003c/em\u003e and 3 specimens of \u003cem\u003eB. s. goniomphalos\u003c/em\u003e. The infection rate among the snails was determined to be 0.42% (6/1,413) (refer to Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The cercariae have an ovate body shape with a surface adorned with spines. The stylet, which is elongated and lacks a shoulder, is positioned at the anterior oral sucker. Notably, the virgulate gland is absent. The prepharynx is relatively short, and the pharynx is positioned close to the oral sucker. Development of the esophagus, ceca, and genitalia did not occur. The excretory vesicle adopts a Y-shaped configuration. Throughout the body, scattered granules and cystogenous glands hinder the observation of the penetration glands. The tail commences immediately after the body's end, appearing relatively short and cylindrical, lacking a finfold, and having an obliterated tail tubule. The cercaria surface is wrinkled and adorned with small spines (Fig.\u0026nbsp;6 and Supplementary File 3).\u003c/p\u003e \u003cp\u003eThe size range and average size (in micrometers, calculated from 10 cercariae) are detailed below:\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabc\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e116\u0026ndash;251 \u0026micro;m (avg. 172 \u0026micro;m) \u0026times; 76\u0026ndash;115 \u0026micro;m (avg. 91 \u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStylet\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u0026ndash;8 \u0026micro;m (avg. 5.6 \u0026micro;m) \u0026times; 2\u0026ndash;4 \u0026micro;m (avg. 2.8 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePharynx\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u0026ndash;14 \u0026micro;m (avg. 8 \u0026micro;m) \u0026times; 6\u0026ndash;17 \u0026micro;m (avg. 11 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29\u0026ndash;43 \u0026micro;m (avg. 35 \u0026micro;m) \u0026times; 26\u0026ndash;41 \u0026micro;m (avg. 31 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVentral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u0026ndash;34 \u0026micro;m (avg. 29 \u0026micro;m)23\u0026ndash;32 \u0026micro;m (avg. 26 \u0026micro;m) \u0026times;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExcretory bladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17\u0026ndash;25 \u0026micro;m (avg. 21 \u0026micro;m) \u0026times; 18\u0026ndash;26 \u0026micro;m (avg. 21 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTail\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e89\u0026ndash;144 \u0026micro;m (avg. 104 \u0026micro;m) \u0026times; 20\u0026ndash;37 \u0026micro;m (avg. 27 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eType 3. Virgulate xiphidiocercariae\u003c/h2\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003eFamily: Lecithodendriidae (L\u0026uuml;he 1901) sensu Odhner, 1910\u003c/h2\u003e \u003cdiv id=\"Sec21\" class=\"Section4\"\u003e \u003ch2\u003eLoxogenoides bicolor\u003c/h2\u003e \u003cp\u003eCercariae were detected in 6 specimens of \u003cem\u003eB. s. siamensis\u003c/em\u003e and 5 specimens of \u003cem\u003eB. s. goniomphalos\u003c/em\u003e, resulting in an infection rate of 0.78% (11/1,413) of the total number of collected snails (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). These cercariae possess an oval shape with a spiny surface adorned throughout with granules. The oral sucker, which is larger than the ventral sucker, is globular and contains an internal stylet, which is present with shouldering. A large virgular organ is located near the oral sucker. The pharynx is distinct, and neither the esophagus nor the ceca were observed. Three pairs of penetration glands are present, located at approximately two-thirds of the body length; the anterior pairs consist of fine granules, while the two posterior pairs contain relatively coarse, dark granules. A U-shaped excretory bladder is present. The tail of the cercaria is spinose and shorter than the body (Fig.\u0026nbsp;7 and Supplementary File 4).\u003c/p\u003e \u003cp\u003eThe size range and average size (in micrometers, calculated from 10 cercariae) are detailed below:\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabd\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e72\u0026ndash;124 \u0026micro;m (avg. 101 \u0026micro;m) \u0026times; 52\u0026ndash;87 \u0026micro;m (avg. 74 \u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStylet\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8\u0026ndash;16 \u0026micro;m (avg. 12 \u0026micro;m) \u0026times; 3\u0026ndash;5 \u0026micro;m (avg. 4 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePharynx\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9\u0026ndash;10 \u0026micro;m (avg. 9.5 \u0026micro;m) \u0026times; 6\u0026ndash;8 \u0026micro;m (avg. 7 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21\u0026ndash;32 \u0026micro;m (avg. 28 \u0026micro;m) \u0026times; 20\u0026ndash;28 \u0026micro;m (avg. 23 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVentral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9\u0026ndash;17 \u0026micro;m (avg. 15 \u0026micro;m) \u0026times; 11\u0026ndash;17 \u0026micro;m (avg. 15 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExcretory bladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23\u0026ndash;31 \u0026micro;m (avg. 27 \u0026micro;m) \u0026times; 12\u0026ndash;23 \u0026micro;m (avg. 17 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTail\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e72\u0026ndash;109 \u0026micro;m (avg. 93 \u0026micro;m) \u0026times; 27\u0026ndash;34 \u0026micro;m (avg. 29 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003eType 4 Parapleurolophocercous cercariae\u003c/h2\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003eFamily: Heterophyidae (Leiper, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1909\u003c/span\u003e) Odhner, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e1914\u003c/span\u003e\u003c/h2\u003e \u003cdiv id=\"Sec24\" class=\"Section4\"\u003e \u003ch2\u003eStictodora tridactyla\u003c/h2\u003e \u003cp\u003eCercariae were detected in 2 specimens of \u003cem\u003eB. s. siamensis\u003c/em\u003e, resulting in an infection rate of 0.14% (2/1,413) of the total number of collected snails (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The cercarial body exhibits an oval shape, and the cuticle is covered with spines. Additionally, delicate bristles are present laterally on the cuticle. A pair of pigmented eyespots is present. The oral sucker is well developed and globular, while the pharynx is small. Seven pairs of penetration glands are located between the pharynx and the anterior margins of the excretory bladder; the ducts are distinct in the oral sucker area. They pass from the penetration glands to terminate near the anterior end of the body. The cystogenous glands are located laterally from slightly below the eyespots to the posterior end of the body. The excretory bladder is thick-walled and V-shaped. The tail of the cercaria is longer than the body and features both lateral and dorsoventral finfolds on each side (Fig.\u0026nbsp;8 and Supplementary File 5).\u003c/p\u003e \u003cp\u003eThe size range and average size (in micrometers, calculated from 10 cercariae) are detailed below:\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabe\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e127\u0026ndash;256 \u0026micro;m (avg. 184 \u0026micro;m) \u0026times; 91\u0026ndash;120 \u0026micro;m (avg. 101 \u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEyespots\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u0026ndash;13 \u0026micro;m (avg. 8 \u0026micro;m) \u0026times; 4\u0026ndash;10 \u0026micro;m (avg. 7 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOral sucker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33\u0026ndash;47 \u0026micro;m (avg. 39 \u0026micro;m) \u0026times; 31\u0026ndash;37 \u0026micro;m (avg. 35 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExcretory bladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33\u0026ndash;72 \u0026micro;m (avg. 53 \u0026micro;m) x 18\u0026ndash;43 \u0026micro;m (avg. 27 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTail\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e396\u0026ndash;435 \u0026micro;m (avg. 407 \u0026micro;m) \u0026times; 29\u0026ndash;45 \u0026micro;m (avg. 33 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLateral finfold\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e139\u0026ndash;256 \u0026micro;m (avg. 199 \u0026micro;m) \u0026times; 12\u0026ndash;26 \u0026micro;m (avg. 16 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDorso-ventral finfold\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e212\u0026ndash;256 \u0026micro;m (avg. 236 \u0026micro;m) \u0026times; 11\u0026ndash;32 \u0026micro;m (avg. 22 \u0026micro;m)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003eCercarial Molecular Characterization: Insights from Genetic Analysis\u003c/h2\u003e \u003cp\u003eIn this study, examination of trematode infections in \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e revealed three distinct cercarial types. All trematodes were subjected to amplification using \u003cem\u003eITS2\u003c/em\u003e subsequences of approximately 350\u0026ndash;800 base pairs to generate a phylogenetic lineage through maximum likelihood analysis. The resulting sequences were compared with \u003cem\u003eITS2\u003c/em\u003e sequences from GenBank (refer to Fig.\u0026nbsp;9 and Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eList of internal transcribed spacer 2 (\u003cem\u003eITS2\u003c/em\u003e) sequences used for phylogenetic analysis.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies of trematode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVoucher code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGenBank accession number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eStage of trematode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReferences\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eEchinochasmus pelecani\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLamet 2, Chaiya District, Surat Thani Province, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0122028.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP460908\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCercaria\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eThis study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eEchinochasmus japonicus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eKT873310.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBesprozvannykh et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eKT873311.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cem\u003eEchinostoma revolutum\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThung 2, Chaiya District,\u003c/p\u003e \u003cp\u003eSurat Thani Province, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0122031.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP460909\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCercaria\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eThis study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eIndiana\u003c/em\u003e, United States of\u0026nbsp;\u003cem\u003eAmerica\u003c/em\u003e.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAF067850.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAdult\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSorensen et al. (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e1998\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGrigorevo, Bulgaria\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAY168930.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eKostadinova and Gibson (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2003\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cem\u003eLoxogenoides bicolor\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHadpunkrai 1, Mueang District, Chumphon Province, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSUT 0122032.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePP460910\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCercaria\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eThis study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBan Purakom (Phachi drainage, Mae Klong River system), Suan Phueng District, Ratchaburi Province, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMH991970.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCercaria\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eVeeravechsukij et al. (\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTat Duen waterfall (Yom drainage, Chao Phraya River system), Si Satchanalai District, Sukhothai Province, Thailand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMH991971.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eAngiostrongylus cantonensis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHQ540551.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLiu (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2010\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn the resultant phylogenetic tree, the trematodes clustered into three distinct groups that were rooted using the nematode \u003cem\u003eAngiostrongylus cantonensis\u003c/em\u003e (HQ540551.1; Liu \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) as an outgroup to ensure notable associations. Clusters 1 and 2 comprised Echinostome cercariae, with Cluster 1 including sequences from \u003cem\u003eEchinochamus japonicus\u003c/em\u003e (KT873310.1, KT873311.1; Besprozvannykh et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and \u003cem\u003eEchinochamus pelecani\u003c/em\u003e obtained from \u003cem\u003eB. s. goniomphalos\u003c/em\u003e from Lamed 2, Chaiya District, Surat Thani Province, Thailand (SUT0122028.3; this study). Cluster 2 represented \u003cem\u003eEchinostoma revolatum\u003c/em\u003e obtained from \u003cem\u003eB. s. goniomphalos\u003c/em\u003e from Thung 2, Chaiya District, Surat Thani Province, Thailand (SUT0122031.1; this study), as well as \u003cem\u003eE. revolutum\u003c/em\u003e from Indiana, U.S.A. (AF067850.1; Sorensen et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) and from Grigorevo, Bulgaria (AY068930.1; Kostadinova et al. 2003). Cluster 3 represented Xiphidiocercariae, consisting of \u003cem\u003eL. bicolor\u003c/em\u003e obtained from \u003cem\u003eB. s. goniomphalos\u003c/em\u003e in Bang Luk, Mueang District, Chumphon Province, Thailand (SUT0122032.2; this study), which clustered with \u003cem\u003eL. bicolor\u003c/em\u003e from Thailand and was reported to infect \u003cem\u003eTarebia granifera\u003c/em\u003e (MH991970.1, MH 991971.1, MH991985.1; Veeravechsukij et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) with high confidence. Thus, this phylogenetic lineage reveals relationships among the species and distinct cercarial types, confirming morphological distinctions.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec27\" class=\"Section2\"\u003e \u003ch2\u003e\u003cem\u003eBithynia snails\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eSnails are commonly found in various aquatic habitats across tropical regions, with certain species significantly impacting public health due to their role as intermediate hosts for many parasitic diseases. The presence of certain snail species, such as \u003cem\u003eBithynia\u003c/em\u003e spp., in major water development projects in Southeast Asia can have adverse effects on socioeconomic development, as they may contribute to the spread of snail-borne parasitic diseases. Diseases transmitted by snails, particularly opisthorchiasis and echinostomiasis, are considered significant public health concerns in this region.\u003c/p\u003e \u003cp\u003eBithyniidae snails, which are found across continents and the Indo-Pacific Islands, typically exhibit small sizes ranging from 6.5 to 14.8 mm in length and 3.0 to 9.6 mm in diameter. These snails are characterized by ovate-conoidal shells, often in brownish, corneous, or olive colors, with delicate spiral lines instead of pronounced sculpturing. The aperture of their shells tends to be round or ovate, featuring a calcareous operculum typically possessing a paucispiral nucleus. While the Bithyniidae family encompasses numerous genera and species, only a select few within the genus Bithynia hold medical significance.\u003c/p\u003e \u003cp\u003eWithin the genus Bithynia, further classification revealed two subgenera: \u003cem\u003eGabbia\u003c/em\u003e and \u003cem\u003eDigoniostoma\u003c/em\u003e. The \u003cem\u003eGabbia\u003c/em\u003e subgenus includes species such as \u003cem\u003eBithynia\u003c/em\u003e (\u003cem\u003eGabbia\u003c/em\u003e) \u003cem\u003ewykojfi\u003c/em\u003e, \u003cem\u003eB.\u003c/em\u003e (\u003cem\u003eG.\u003c/em\u003e) \u003cem\u003ewalkeri\u003c/em\u003e, and \u003cem\u003eB.\u003c/em\u003e (\u003cem\u003eG\u003c/em\u003e.) \u003cem\u003epygmaea\u003c/em\u003e, none of which are medically significant. Conversely, the \u003cem\u003eDigoniostoma\u003c/em\u003e subgenus comprises species such as \u003cem\u003eBithynia\u003c/em\u003e (\u003cem\u003eDigoniostoma\u003c/em\u003e) \u003cem\u003efuniculata\u003c/em\u003e, \u003cem\u003eB.\u003c/em\u003e (\u003cem\u003eD.\u003c/em\u003e) \u003cem\u003esiamensis\u003c/em\u003e, and \u003cem\u003eB.\u003c/em\u003e (\u003cem\u003eD.\u003c/em\u003e) \u003cem\u003epulchella\u003c/em\u003e, which, except for \u003cem\u003eB. pulchella\u003c/em\u003e, are medically important. The morphological characteristics and geographical distribution of \u003cem\u003eB. siamensis\u003c/em\u003e, which is classified into two different subspecies, \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s\u003c/em\u003e. \u003cem\u003egoniomphalos\u003c/em\u003e, are important. The specific characteristics utilized in the classification of \u003cem\u003eB. funiculata\u003c/em\u003e, \u003cem\u003eB. s. siamensis\u003c/em\u003e, and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (Tropmed Technical Group \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Petney et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Although \u003cem\u003eB. s. goniomphalos\u003c/em\u003e has been reported throughout the Lower Mekong Basin, this species is predominantly found in northeast Thailand. Here, we present findings on the populations of both subspecies of \u003cem\u003eB. siamensis\u003c/em\u003e found in southern Thailand. These snails predominantly inhabit freshwater environments, particularly rice fields, ponds, and irrigation canals. Our study focused on differentiating \u003cem\u003eBithynia\u003c/em\u003e subspecies based on morphological shell characteristics, with molecular analysis for confirmation. Molecular analysis was conducted to confirm the identification of \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e snails collected from the southern region of Thailand based on their shell morphology and sculptures. The nucleotide sequences of \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e from this study clustered together with their respective species and were clearly separated from those found in the north, northeast, and central regions of Thailand.\u003c/p\u003e \u003cp\u003eAccording to phylogenetic lineage, the distributions of \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e underscore the significant role of snail cluster differentiation over species differentiation, given their categorization within the same species (\u003cem\u003eBithynia siamensis\u003c/em\u003e) and their closely similar shell morphology. \u003cem\u003eB. s. siamensis\u003c/em\u003e typically exhibits a conical shell with a pointed apex and a rounded base, featuring a tightly coiled structure with light greenish-brown coloration and a glossy surface. In contrast, \u003cem\u003eB. s. goniomphalos\u003c/em\u003e has a thicker shell with brownish coloration and a matte surface. These subtle differences in shell morphology necessitate the use of \u003cem\u003ecox1\u003c/em\u003e sequences to confirm species categorizations (Duangprompo et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Kulsantiwong et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Tantrawatpan et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Bunchom et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAs a result, the differentiation between \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e based on shell morphology was validated, with both subspecies clustering with their respective species and showing close relationships to each other. In the present study, we confirmed the presence of both \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e in the southern region of Thailand. Moreover, both \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e serve as the first intermediate hosts of trematode infections in the study areas.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec28\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003eParasitic Infections of Bithynia Snails\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eThrough subspecies differentiation, we determined the prevalence of trematodes in both \u003cem\u003eB. siamensis\u003c/em\u003e subspecies. However, the \u003cem\u003eBithynia s. goniomphalos\u003c/em\u003e subspecies was present only in three provinces (not all five provinces), namely, Nakhon Si Thammarat Province, Surat Thani Province, and Chumphon Province. The prevalence of trematode infections in these provinces was assessed in the present study, in which both Bithynia subspecies were found. Seventeen snails of 569 \u003cem\u003eB. s. goniomphalos\u003c/em\u003e were infected with four species of trematodes belonging to three classes of cercariae: Echinostome cercariae, Armatae xiphidiocercariae, and Virgulate xiphidiocercariae. Fifty-three of 844 \u003cem\u003eB. s. siamensis\u003c/em\u003e snails were infected with four species of trematodes belonging to four classes of cercariae: Echinostome cercariae, Armatae xiphidiocercariae, Virgulate xiphidiocercariae, and Parapleurolophocercous cercariae. According to previous reports, \u003cem\u003eB. s. goniomphalos\u003c/em\u003e has been reported as the first intermediate host of many types of cercariae, including Amphistome cercariae, Cystophorous cercariae, Echinostome cercariae, Furcocercous cercariae, Monostome cercariae, Mutabile cercariae, Parapleurolophocercous cercariae, Pleurolophocercous cercariae, Amartae xiphidiocercariae, and Virgulate xiphidiocercariae, whereas \u003cem\u003eB. s. siamensis\u003c/em\u003e has also been reported as an intermediate host of cercarial types, including Amphistome cercariae, Gymnocephalous cercariae, Monostome cercariae, Parapleurolophocercous cercariae, Pleurolophocercous cercariae, Strigea cercariae, and Virgulate xiphidiocercariae (Nithiuthai et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Sri-Aroon et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Chontananarth and Wongsawad \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Kulsantiwong et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Sripa et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Nguyen et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Krailas et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, many reports have differentiated only the cercarial type and not the species of cercariae. In our study, we differentiated the cercarial species using morphology, organ characteristics, and genetic analysis. Five species of cercariae belonging to four families were identified: (1) the family Echinostomatidae, which consists of \u003cem\u003eE. pelecani\u003c/em\u003e and \u003cem\u003eE. revolutum\u003c/em\u003e; (2) the family Haematoloechidae, \u003cem\u003eH. similis\u003c/em\u003e; (3) the family Lecithodendriidae, \u003cem\u003eL. bicolor\u003c/em\u003e; and (4) the family Heterophyidae, \u003cem\u003eS. tridactyla\u003c/em\u003e. These cercariae are Echinostoma cercariae, Armatae xiphidiocercariae, Virgulate xiphidiocercariae, and Parapleurolophocercous cercariae.\u003c/p\u003e \u003cp\u003eEchinostome cercariae were found to comprise two species belonging to two subfamilies: the first subfamily was Echinochasminae, and the second subfamily was Echinostomatinae. These species were \u003cem\u003eE. pelecani\u003c/em\u003e and \u003cem\u003eE. revolutum\u003c/em\u003e. \u003cem\u003eE. pelecani\u003c/em\u003e was found in Surat Thani Province (SUT 0122028: Lamet 2, Chaiya District) and Chumphon Province (SUT 0122032: Hadpunkrai 1, Mueang District). This trematode has never been reported in the southern part of Thailand or in the Bithynia snail host, but this species has been reported in \u003cem\u003eMelanoides tuberculata\u003c/em\u003e in the eastern region of Thailand (Krailas et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). \u003cem\u003eE. pelecani\u003c/em\u003e was reported in 42 \u003cem\u003eB. s. siamensis\u003c/em\u003e and 4 \u003cem\u003eB. s. goniomphalos\u003c/em\u003e snails, with an infection rate of 3.26% (46/1413). This trematode was the most prevalent among the other trematodes in this study. \u003cem\u003eE. pelecani\u003c/em\u003e was first isolated from the small intestine of a pelican (\u003cem\u003ePelecanus conspicillatus\u003c/em\u003e) at Tailem Bend, Murray River, Australia (Johnston and Simpson \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1944\u003c/span\u003e). Even though the worms were of the Echinostoma cercaria type, the cercaria lost its collar spines. In our study, we differentiated \u003cem\u003eE. pelecani\u003c/em\u003e using morphological and internal organ characteristics. The morphological character of the body shape distinguishes the cercaria, which shows an oral sucker with three duct openings. Moreover, we analyzed the genetics of the emerging cercariae collected from \u003cem\u003eBithynia\u003c/em\u003e snails to confirm the results of this study. The definitive host of \u003cem\u003eE. pelecani\u003c/em\u003e includes several fish-eating birds and mammals; this parasite primarily affects avian hosts, and its complex life cycle involving snails and other aquatic organisms poses risks to human health. Ingestion of contaminated water or undercooked fish containing infective larvae can lead to human infection, resulting in symptoms such as abdominal pain, diarrhea, and malaise (Toledo and Fried \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). This is crucial for assessing its impact on public health. Furthermore, \u003cem\u003eEchinochasmus\u003c/em\u003e infections have been reported worldwide, highlighting the global significance of studying and monitoring these parasites for effective control measures (Chai et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). \u003cem\u003eE. revolutum\u003c/em\u003e was also found in Surat Thani Province (SUT 0122031: Thung 2, Chaiya District). In this study, \u003cem\u003eE. revolutum\u003c/em\u003e was reported in 5 \u003cem\u003eB. s. goniomphalos\u003c/em\u003e snails, with an infection rate of 0.35% (5/1413). This parasite was the first Echinostome species discovered in the intestinal flukes of ducks and described in the literature. Infections primarily affect avian hosts; however, accidental ingestion of infected intermediate hosts by humans or other mammals can lead to intestinal infections, causing symptoms such as abdominal pain, diarrhea, and malnutrition. In veterinary medicine, infections in domestic animals, particularly poultry, can result in economic losses due to decreased productivity and mortality (Chai \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Fried et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Furthermore, \u003cem\u003eE. revolutum\u003c/em\u003e serves as a model organism for studying host-parasite interactions and the immunology of trematode infections, contributing valuable insights to broader parasitological research. Previous reports have shown that \u003cem\u003eE. revolutum\u003c/em\u003e is found worldwide, including in Asia, Europe, Africa, Australia, New Zealand, and the Americas. The second intermediate host was the snail genus \u003cem\u003eFilopaludina\u003c/em\u003e, which is popular in Asian food. Eating raw or improperly cooked snails can cause human echinostomiasis. It is likely that since \u003cem\u003eE. pelecani\u003c/em\u003e was reported to successfully encyst in fish (\u003cem\u003eOryzias latipes\u003c/em\u003e, \u003cem\u003eGambusia affinis\u003c/em\u003e), it can also do so in snails (\u003cem\u003eLymnaea lessoni\u003c/em\u003e, \u003cem\u003eAmeria\u003c/em\u003e spp.) and tadpoles (\u003cem\u003eCrinia\u003c/em\u003e sp.). However, both \u003cem\u003eE. pelecani\u003c/em\u003e and \u003cem\u003eE. revolutum\u003c/em\u003e exemplify the complexity of trematode parasites and their intricate relationships with various hosts. Their widespread distribution, diverse host range, and implications for both veterinary and human health underscore the importance of continued research into the biology, ecology, and control strategies of this fascinating parasite (Kostadinova and Gibson \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Chai \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Fried et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cem\u003eH. similis\u003c/em\u003e is a parasite belonging to the family Haematoloechidae. This species can be distinguished as a Xiphidiocercariae type, presenting a stylet in the oral sucker. The genus Haematoloechus has been reported in all zoogeographical regions and is found in the lungs of various anurans (Kim et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). In this study, \u003cem\u003eH. similis\u003c/em\u003e was categorized based on the morphological distinction of cercariae. The stylet is a typical structure of the xiphidiocercariae type. Although at least six subgroups of xiphidiocercariae are known (Schell \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1970\u003c/span\u003e), we described \u003cem\u003eH. similis\u003c/em\u003e as belonging to the subgroup of Armatae xiphidiocercariae, where the tail is shorter than the body, the dorsoventral finfold is absent, the virgula organ is not found, and the oral and ventral suckers are of equal size. Armatae xiphidiocercariae have been reported as the trematode present in the family Plagiorchidae and include \u003cem\u003eH. similis\u003c/em\u003e (Grabda \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1960\u003c/span\u003e; Falt\u0026yacute;nkov\u0026aacute; et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Many \u003cem\u003eHaematoloechus\u003c/em\u003e species have been described in the family Haematoloechidae and are characterized by a typical tail structure with the presence of fin folds, indicating the subgroup of Ornatae xiphidiocercariae, order Plagiorchiiformes Olsen \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e1974\u003c/span\u003e. Here, we present \u003cem\u003eH. similis\u003c/em\u003e, which belongs to the family Haematoloechidae and is characterized by simple-tailed xiphidiocercariae without a finfold and a stylet without shouldering (Yamaguti \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e1975\u003c/span\u003e). The cercaria were found in Surat Thani Province (SUT 0122028: Lamet 2, Chaiya District) and Chumphon Province (SUT 0122033: Hadpunkrai 2, Mueang District). They were found in 3 \u003cem\u003eB. s. siamensis\u003c/em\u003e and 3 \u003cem\u003eB. s. goniomphalos\u003c/em\u003e snails, with an infection rate of 0.42% (6/1413). \u003cem\u003eH. similis\u003c/em\u003e has been reported in various regions of Thailand, with the thiarid snail \u003cem\u003eM. tuberculata\u003c/em\u003e recorded as the first intermediate host, with an infection rate of 1.46% (468/32,026) (Krailas et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe other Xiphidiocercariae type, belonging to the subgroup Virgulate xiphidiocercariae, has a virgular organ present in the region of the oral sucker. This virgular organ is used for the storage of mucoid secretions and is thought to provide some protection for the cercaria and aid in attachment to substrate materials (Schell \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1970\u003c/span\u003e). \u003cem\u003eL. bicolor\u003c/em\u003e, the most common parasite, has been reported to infect many snail species, such as thiarid snails (\u003cem\u003eM. tuberculata\u003c/em\u003e, \u003cem\u003eT. granifera\u003c/em\u003e, \u003cem\u003eThiara\u003c/em\u003e (i.e., \u003cem\u003eMieniplotia\u003c/em\u003e) \u003cem\u003escraba\u003c/em\u003e, and \u003cem\u003eStenomelania\u003c/em\u003e sp.) (Dechruksa et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Ukong et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Krailas et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Veeravechsukij et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Apiraksena et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and pachychilid snails (\u003cem\u003eBrotia costula\u003c/em\u003e, \u003cem\u003eBrotia dautzenbergiana\u003c/em\u003e, and \u003cem\u003eBrotia wykoffi\u003c/em\u003e) (Pratumsrikajorn et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Many previous studies have reported on virgulate cercariae infections in \u003cem\u003eBithynia\u003c/em\u003e snails but did not specify the species of the emerging cercariae (Chontananarth and Wongsawad \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Kulsantiwong et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Sripa et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Pitaksakulrat et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Interestingly, \u003cem\u003eL. bicolor\u003c/em\u003e is the most common parasite found in almost all studies; it has a high prevalence in collected snails and is distributed in every water body system. In our study, \u003cem\u003eL. bicolor\u003c/em\u003e was detected in 6 specimens of \u003cem\u003eB. s. siamensis\u003c/em\u003e and 5 specimens of \u003cem\u003eB. s. goniomphalos\u003c/em\u003e, resulting in an infection rate of 0.78% (11/1,413). The cercariae were found in Nakhon Si Thammarat Province (SUT 0122015: Bo Lo 2, Chian Yai District) and Chumphon Province (SUT 0122032: Hadpunkrai 1, Mueang District; SUT 0122034: Bang Luk, Mueang District). This Virgulate xiphidiocercariae is produced by trematodes from the family Lecithodendriidae; we reported another Virgulate xiphidiocercariae, \u003cem\u003eLoxogenes liberum\u003c/em\u003e, infecting \u003cem\u003eB. s. siamensis\u003c/em\u003e from Chana District, Songkhla Province, in a previous article (Krailas et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). These findings confirm that the \u003cem\u003eBithynia\u003c/em\u003e snail is a common intermediate host of Virgulate xiphidiocercariae.\u003c/p\u003e \u003cp\u003eOne of the trematodes in the family Heterophyidae, \u003cem\u003eS. tridactyla\u003c/em\u003e, a Parapleurolophocercous cercariae type, was reported to occasionally infest brackish water and marine snails, while metacercariae encyst in fish, with the definitive hosts being birds and mammals, including humans. Like other heterophyid trematodes, \u003cem\u003eS. tridactyla\u003c/em\u003e can have significant implications for both wildlife and human health. While these parasites primarily infect birds, they can also infect fish species consumed by humans, leading to potential zoonotic infections. The consumption of undercooked or raw fish containing infective larvae can result in human intestinal infections, causing symptoms such as abdominal pain, diarrhea, and nausea (Chai et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1988\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2005\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Elsheikha and Elshazly \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). In our previous study, we reported that \u003cem\u003eS. tridactyla\u003c/em\u003e was found in thiarid snails such as \u003cem\u003eM. tuberculata\u003c/em\u003e, \u003cem\u003eM. jugicostis\u003c/em\u003e, and \u003cem\u003eT. granifera\u003c/em\u003e (Ukong et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Krailas et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Veeravechsukij et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In this study, we identified \u003cem\u003eS. tridactyla\u003c/em\u003e in Chumphon Province (SUT 0122032: Hadpunkrai 1, Mueang District). This species was detected in 2 \u003cem\u003eB. s. siamensis\u003c/em\u003e snails, with an infection rate of 0.14% (2/1413). Likewise, the presence of Parapleurolophocercous cercariae raises concerns due to the potential transmission of other pathogens and contaminants through contaminated water sources. Additionally, the consumption of raw or undercooked fish infected with \u003cem\u003eS. tridactyla\u003c/em\u003e metacercariae can lead to human infections with other trematode species, such as the liver flukes \u003cem\u003eO. viverrini\u003c/em\u003e and \u003cem\u003eC. sinensis\u003c/em\u003e or the intestinal flukes \u003cem\u003eHaplorchis\u003c/em\u003e spp. and \u003cem\u003eMetagonimus\u003c/em\u003e spp., posing risks to public health.\u003c/p\u003e \u003cp\u003eIn this study, two provinces did not harbor infected \u003cem\u003eBithynia\u003c/em\u003e snails, but in a previous study, we reported three species of trematodes from \u003cem\u003eBithynia s. siamensis\u003c/em\u003e, namely, \u003cem\u003eGastrothylax crumenifer\u003c/em\u003e, \u003cem\u003eAstiotrema monticellii\u003c/em\u003e, and \u003cem\u003eLoxogenes liberum\u003c/em\u003e, in Chana District, Songkhla Province (Krailas et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This confirms that \u003cem\u003eBithynia\u003c/em\u003e snails are important trematode-transmitting snails in the southern region of Thailand. The lack of genetic analysis for the cercariae that were not included (i.e., \u003cem\u003eHaematoloechus similis\u003c/em\u003e and \u003cem\u003eStictodora tridactyla\u003c/em\u003e) in this phylogenetic lineage results from the insufficient number of cercariae for genomic DNA extractions; however, the morphological and internal organ characteristics of the cercariae were clearly identified. Additionally, research on the prevalence and distribution of trematodes and transmitting snails can be useful in medical and veterinary fields. The presence of these parasites in both humans and animals underscores the importance of continued research and vigilance in monitoring and controlling trematode infections to protect human and animal health.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003e \u003cem\u003eBithynia\u003c/em\u003e snails are recognized for their medical significance due to their role as intermediate hosts of trematodes. The prevalence and distribution of trematode-transmitting snails, specifically \u003cem\u003eB. siamensis\u003c/em\u003e, were studied in southern Thailand. Both \u003cem\u003eB. s. siamensis\u003c/em\u003e and \u003cem\u003eB. s. goniomphalos\u003c/em\u003e specimens were collected, and cercarial infection analysis was conducted to identify trematodes at the larval stage. The morphological and internal organ characteristics of the cercariae allowed for the categorization of trematodes into five species: \u003cem\u003eE. pelecani\u003c/em\u003e, \u003cem\u003eE. revolutum\u003c/em\u003e, \u003cem\u003eH. similis\u003c/em\u003e, \u003cem\u003eL. bicolor\u003c/em\u003e, and \u003cem\u003eS. tridactyla\u003c/em\u003e. This research holds potential utility in both medical and veterinary fields. The presence of these parasites in both humans and animals underscores the importance of continued research and vigilance in monitoring and controlling trematode infections to protect human and animal health.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAll authors have read and agreed to the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe financial support came from the Faculty of Science, grant \u003cu\u003eno.\u0026nbsp;\u003c/u\u003e\u003cu\u003eSRIF-JRG-2567-06\u003c/u\u003e, and the \u003cu\u003eThailand Science Research and Innovation (TSRI) National Science, Research and Innovation Fund (NSRF) (Fiscal Year 2024)\u003c/u\u003e\u003cu\u003e,\u003c/u\u003e\u003cu\u003e\u0026nbsp;\u003c/u\u003e\u003cu\u003eproject no. 4691774\u003c/u\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eData Availability\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eCode Availability\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eAuthors\u0026apos; Contributions\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization and Experiment Design: DK, TW; Field Work: DK, TW, JK, CJ, PT; Laboratory Work: DK, TW, JK; Data Analysis: DK, TW, JK, NV, WD, SS, KT, MG; Manuscript Preparation: DK, TW, JK, NV, MG\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eCompliance with Ethical Standards\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors of this study affirm that all research methods employed in this investigation strictly adhere to the ethical standards established by national and institutional committees concerning the welfare and utilization of laboratory animals. Prior approval for this study was obtained from the Committee for Animal Scientific Research at Silpakorn University, Thailand, under reference number 20/2565.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eCompeting Interests\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors declare that there is no conflict of interest.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eResearch Involving Humans and Animals\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cstrong\u003e\u003cem\u003eInformed consent\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cbr\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eApiraksena K, Namchote S, Komsuwan J, Dechraksa W, Tharapoom K, Veeravechsukij N, Glaubrecht M, Krailas D (2020) Survey of \u003cem\u003eStenomelania\u003c/em\u003e Fisher, 1885 (Cerithioidea, Thiaridae): the potential of trematode infections in a newly-recorded snail genus at the coast of Andaman Sea, South Thailand. 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Br J Surg 89:962-970. https://doi.org/10.1046/j.1365-2168.2002.02143.x\u003c/li\u003e\n\u003cli\u003eWongpim T, Komsuwan J, Janmanee C, Thongchot P, Limsampan S, Wichiannarat N, Chaowatut W, Suwanrat S, Dechruksa W, Veeravechsukij N, Glaubrecht M, Krailas D (2023) Freshwater pulmonate snails and their potential role as trematode intermediate host in a cercarial dermatitis outbreak in Southern Thailand. Evol Syst 7:293-315. https://doi.org/10.3897/evolsyst.7.107847\u003c/li\u003e\n\u003cli\u003eYamaguti S (1971) Synopsis of digenetic trematodes of vertebrates. Vol. I. Keigaku Publishing Co., Tokyo, Japan\u003c/li\u003e\n\u003cli\u003eYamaguti S (1975) A synoptical review of life histories of digenetic trematodes of vertebrates. Keigaku Pub. Co., Kyoto, Japan\u003c/li\u003e\n\u003cli\u003eZheng S, Zhu Y, Zhao Z, Wu Z, Okanurak K, Lv Z (2017) Liver fluke infection and cholangiocarcinoma: a review. Parasitol Res 116:11-19. https://doi.org/10.1007/s00436-016-5276-y\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"parasitology-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pare","sideBox":"Learn more about [Parasitology Research](http://link.springer.com/journal/436)","snPcode":"436","submissionUrl":"https://submission.nature.com/new-submission/436/3","title":"Parasitology Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Bithynia siamensis, trematode infection, southern Thailand, Echinostome cercariae, Xiphidiocercariae, Parapleurolophocercous cercariae","lastPublishedDoi":"10.21203/rs.3.rs-4464091/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4464091/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study aimed to investigate the occurrence of larval trematode infections in bithyniid snails across five provinces in southern Thailand. A total of 1,413 \u003cem\u003eBithynia siamensis\u003c/em\u003e snails were collected between October 2021 and October 2022 using handpicking and scooping methods. Among these, 844 were identified as \u003cem\u003eB. s. siamensis\u003c/em\u003e and 569 as \u003cem\u003eB. s. goniomphalos\u003c/em\u003e. The snail samples were examined for parasitic infections in the laboratory using shedding and crushing methods. Among the 27 sampling sites, snails from 6 sites were infected with various trematode species (infection rate: 4.95%, 70/1,413). Evaluation of the morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of cercariae (belonging to four families). The identified species included \u003cem\u003eEchinochasmus pelecani\u003c/em\u003e (family: Echinostomatidae), \u003cem\u003eEchinostoma revolutum\u003c/em\u003e (family: Echinostomatidae), \u003cem\u003eHaematoloechus similis\u003c/em\u003e (family: Haematoloechidae), \u003cem\u003eLoxogenoides bicolor\u003c/em\u003e (family Lecithodendriidae), and \u003cem\u003eStictodora tridactyla\u003c/em\u003e (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively.\u003c/p\u003e","manuscriptTitle":"Prevalence and Distribution of the Trematode-Transmitting Snail Bithynia siamensis in Southern Thailand","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-07 08:28:41","doi":"10.21203/rs.3.rs-4464091/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-07-05T23:09:54+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-30T18:00:17+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-28T07:43:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"317253706223193178180648100095934619837","date":"2024-05-30T07:32:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"121880803048272084929960295442356574248","date":"2024-05-30T05:10:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"12260197259442296509704787464942952737","date":"2024-05-29T09:51:09+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-28T11:31:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-27T08:28:32+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-05-27T05:37:57+00:00","index":"","fulltext":""},{"type":"submitted","content":"Parasitology Research","date":"2024-05-23T04:15:45+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"parasitology-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pare","sideBox":"Learn more about [Parasitology Research](http://link.springer.com/journal/436)","snPcode":"436","submissionUrl":"https://submission.nature.com/new-submission/436/3","title":"Parasitology Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"5064bd80-3950-4b85-9f11-15ac3f11b8c6","owner":[],"postedDate":"June 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-10-07T16:01:29+00:00","versionOfRecord":{"articleIdentity":"rs-4464091","link":"https://doi.org/10.1007/s00436-024-08345-4","journal":{"identity":"parasitology-research","isVorOnly":false,"title":"Parasitology Research"},"publishedOn":"2024-10-01 15:57:32","publishedOnDateReadable":"October 1st, 2024"},"versionCreatedAt":"2024-06-07 08:28:41","video":"","vorDoi":"10.1007/s00436-024-08345-4","vorDoiUrl":"https://doi.org/10.1007/s00436-024-08345-4","workflowStages":[]},"version":"v1","identity":"rs-4464091","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4464091","identity":"rs-4464091","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}