Prevalence of parasites in freshwater snails with notes on helminth-associated diseases in Balo-i Lake, Lanao del Norte, Philippines

Prevalence of parasites in freshwater snails with notes on helminth-associated diseases in Balo-i Lake, Lanao del Norte, Philippines | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Prevalence of parasites in freshwater snails with notes on helminth-associated diseases in Balo-i Lake, Lanao del Norte, Philippines LEONARDO A. ESTANO, Johanisah D. Bari, Lady Jane G. Morilla, Leonardo A. Estaño This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4891076/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Feb, 2026 Read the published version in Journal of Parasitic Diseases → Version 1 posted 5 You are reading this latest preprint version Abstract Freshwater snails play crucial roles in aquatic habitats with essential ecosystem functions and services. However, they also serve as intermediate hosts for various parasites that pose risks to human and animal health. This study aimed to identify freshwater snail species with parasite infection and assess parasite prevalence in Balo-i Lake, Lanao del Norte, Philippines. Snail samples were collected from three sites (Power Plant area, Residential area, and Agricultural area) around the lake utilizing the belt transect method, and parasites were identified based on morphological characteristics. Physicochemical parameters were measured to explore their correlation with parasite prevalence. Results revealed a total prevalence rate of 3.78% (95% CI 2.372–5.966) among five freshwater snail species – S. angularis (n = 26), P. acuta (n = 22), M. maculata (n = 81), M. tuberculata (n = 44), and R. quadrasi (n = 5), with notable variations among sampling sites and seasonal variation between wet and dry seasons. M. maculata harbored the most parasites, with three cercarial morphotypes and a nematode. Trematodes were the most abundant parasites, with five morphotypes identified, namely Cercarium cercariae , Gymnocephalous cercariae , Parapleurolophocercous cercaria , Echinostome cercariae , and Strigea cercariae , most of which are produced by intestinal parasites of fish, birds, and mammals. Gymnocephalous cercariae infected most snail individuals (n = 6), but Parapleurolophocercous cercaria was the most common, infecting three snail species across two sampling sites. The residential area has the highest prevalence rate of infection, likely influenced by frequent human activities like bathing, washing clothes, pollution, and the presence of potential hosts such as ducks, amphibians, and mammals in adjacent areas. Weak correlations between parasite prevalence and pH and temperature suggest additional influencing factors. The presence of parasites highlights public health concerns, emphasizing the need for control measures and ecosystem conservation to mitigate disease transmission in the area. cercariae infection lake nematode trematode Figures Figure 1 Figure 2 Introduction Freshwater snails have been widely explored for their role as intermediate host of infectious trematodes and other parasites of animals and humans (Paller et al. 2019 ; Martin and Cabrera, 2018 ; Logronio et al. 2020 ; Cawas et al. 2020 ; Estaño, 2023 ). Some are responsible for several important human diseases such as schistosomiasis (bloodflukes) and fasciolosis (liver flukes) (Vaughn, 2009 ; Jumawan and Estaño, 2021 ). Millions of people in about 90 countries suffer from parasitic diseases transmitted by intermediate hosts freshwater snails. For instance, more than 20 million people are infected with Fasciola hepatica , and more than 200 million people are infected with Schistosoma spp. (Correa et al. 2011 ; Shan et al. 2020 ; Skelly and Da'Dara, 2023 ). Infections pose a public health risk and cause severe socio-economic problems in many tropical and subtropical countries, including the Philippines (Prasopdee et al. 2015 ; Estaño and Jumawan, 2023 ). Balo-i Lake is an artificial lake in the Municipality of Balo-i, Lanao del Norte in the Philippines, that feeds from the larger Lake Lanao in Lanao del Sur through the Agus River. This freshwater ecosystem harbors aquatic plants and animals that support its biodiversity and various livelihoods to the community. It has been a water source for the nearby locals for washing clothes and other domestic use, collecting fish, shrimps, and edible snails (Demayo et al. 2007 ). However, there is a dearth of information on freshwater snails and their associated parasites in the country, and no study has been conducted in the area. This study provides valuable information and updates on the resource utilization of freshwater snails in the different habitats surrounding the lake and the possible diseases associated with these freshwater snails. Materials and Methods The locale of the study The study site, Balo-i Lake (8° 7' 44.7594" N, 124° 12' 1.8" E), is situated in the Municipality of Balo-i, Lanao del Norte. Surrounding the lake are Barangays Nangka, Maria Cristina, Matampay, and Somiorang wherein existing land uses include built-up areas and agriculture (National Power Corporation, 2021). Balo-i Lake is a man-made lake that is part of the Lake Lanao watershed, serving as the reservoir of the Agus IV Hydroelectric Power Plant that is host to three generating units. Balo-i Lake is fed by water flowing from Lake Lanao in Lanao del Sur through the Agus River, which spans 36.5 kilometers (22.7 mi) from Lanao Lake to Iligan Bay. Within the lake, there is a significant accumulation of water hyacinth ( Eichhornia crassipes ) that continues to persist. Three sampling sites were established along the littoral/riparian zone of Balo-i Lake (Fig. 1 ). Sampling Methods Before the collection of samples, necessary permits were acquired from the LGU of Balo-i, and owners of the areas included in the sampling sites were also asked for their permission. Three sampling sites were identified and established namely; Power Plant area, Residential area, and Agricultural area. Sampling site 1 is along the Agus IV Power Plant area (8° 8' 1.017" N, 124° 12' 2.0334" E) thereby it is directly connected to the lake by a riprap wall, serving as the border to where the Agus IV facilities were located. Vegetation is limited, with few grasses, vines, and shrubs. Animals such as birds, insects, and shrimp were also present. The second site was established near residential areas (8° 7' 40.7" N, 124° 12' 28.2" E) where vegetation was more abundant, aside from grasses and vines, ferns, herbaceous plants like taro and banana, and trees were present. Animals such as ducks, insects, amphibians, as well as terrestrial snails were observed in this area. Also, a small fish pond was seen within the site. The third sampling site was near agricultural area (6° 7' 09.1" N, 124° 11' 58.2" E), particularly an openland with abundant coconut trees. Found directly on the lake and lake shore were plants such as Lantana camara , some vines, shrubs, and even a guava tree, as well as animals including ducks, birds, and insects. Livestock mammals such as cows were observed within the area. In all of these sites, the dense water hyacinths in the lake were prominent and pollution were evident, especially in the residential area and Power Plant area. In each sampling site, a belt transect of 100 m in length with a 1 m line perpendicular on both sides of the main transect was established. The collection of snails was done by handpicking along the belt transect lines. Sampling was performed between 6:00 am to 10:00 am. Snail samples collected were placed in containers with lake water, and transported to the laboratory within 2–3 hours after collection. Sampling was done twice, on August, 2023 and March, 2024. Processing and identification samples Each sample was recorded and identified to species level using taxonomic keys, different references, web searches, and previously published studies. Identification guides by Frest and Johannes ( 1999 ), Harold and Guralnick ( 2010 ), Cummings and Lydeard ( 2019 ) were utilized. To assess parasite infection in the samples, each snail was subjected to the crushing method (Caron et al. 2008 ; Jumawan and Estaño, 2021 ) wherein the snails were crushed using mortar and pestle and added few drops of saline solution. Using a dropper, 2–3 drops of the resulting liquid were placed onto a glass slide and viewed using a compound microscope to observe for parasites. Smaller snail samples, with sizes about 1cm or less, were directly crushed using two glass slides and viewed under a microscope. All parasites detected were identified based on morphotype using the classification key and identification manuals of Frandsen and Christensen ( 1984 ), Chontananarth and Wongsawad ( 2013 ), Farahnak, et al. (2006), Van Wyk and Mayhew ( 2013 ), Mohammed, et al. (2015), and Chontananarth, et al. ( 2017 ). Only presence-absence data of parasites were identified in the present study, that is the prevalence of infection or the proportion of infected individuals. Measurement of pH and temperature The physicochemical parameter pH was measured in situ using a multi-tester for every sampling site to study their possible effects on parasite prevalence among freshwater snails. Data Analysis The prevalence of parasite infection was computed using the formula: $$\:Prevalence=\frac{\#\:\text{o}\text{f}\:\text{i}\text{n}\text{f}\text{e}\text{c}\text{t}\text{e}\text{d}\:\text{s}\text{a}\text{m}\text{p}\text{l}\text{e}\text{s}}{\text{t}\text{o}\text{t}\text{a}\text{l}\:\text{n}\text{u}\text{m}\text{b}\text{e}\text{r}\:\text{o}\text{f}\:\text{s}\text{a}\text{m}\text{p}\text{l}\text{e}\text{s}}x\:100\%$$ A 95% confidence level was applied to the prevalence using the OpenEpi Program. Pearson’s correlation coefficient analysis was used to determine the correlation between physicochemical parameters and parasite infection prevalence. Statistical analysis was done using the SPSS version 20.0 software. Results Freshwater snail collected Four hundred fifty snail samples belonging to 9 species were examined for parasite infection. These include Pomacea canaliculata (233) known as an agricultural pest in the ricefield; Sinotaia angularis (26), an edible snail; Tarebia granifera (24); Melanoides tuberculata (44), Melanoides maculata (81), Radix quadrasi (5), Gyraulus sp. (5) Biomphalaria sp. (10) and Physella acuta (22). One hundred eighty-five individuals were collected from the August 2023 sampling, while 265 individuals were from the March 2024 sampling. All these freshwater snail species were of medical importance as they serve as vectors or an intermediate host for various pathogenic parasites such as nematodes and trematodes (Table 1 ). Table 1 Host species and prevalence of parasites in snails of Balo-i Lake, Balo-i, Lanao del Norte, Philippines. Host Snail Species No. of samples examined Number of infected individuals Total Prevalence (%) (CI**) Cer Par Gym Ech Str Nematode P. canaliculata 233 - - - - - - - S. angularis 26 - - - - - - 3.85 (0.68–18.89) P. acuta 22 - 2 2 - - 18.18 (7.31–38.52) Gyraulus sp. 5 - - - - - - - T. granifera 24 - - - - - - - Biomphalaria sp. 10 - - - - - - - M. maculata 81 1 2 6 - - 1 11.11 (5.96–19.79) M. tuberculata 44 - 1 - - - - 2.27 (0.40-11.81) R. quadrasi 5 - - - - 2 - 40.00 (11.76–76.93) **95% Confidence Interval Cer: Cercarium cercaraie, Par: Parapleurolophocercous cercaria, Gym: Gymnocephalous cercariae, Ech: Echinostome cercariae, and Str: Strigea cercariae. Parasites recovered in freshwater snails A total of 5 parasite morphotypes were identified: Cercarium cercariae is a cercarial type characterized by the absence of tail/s. It develops in rediae and encyst in snails. Gymnocephalous cercariae is the cercarial type characterized by an unforked tail, the presence of a ventral sucker on the mid-ventral surface of the body, neither stylet nor spiny collar present, having no eyespots, and numerous cystogenous glands in the body. They develop in rediae and encyst on external substrates. Parapleurolophocercous cercaria is a cercarial type characterized by an unforked tail with well-developed fin folds, ventral sucker vestigial or absent, visible eyespots, and a few cystogenous glands in the body. Echinostome cercariae are characterized by having an unforked tail, a ventral sucker on the mid-ventral surface of the body, an oral sucker without a stylet but are surrounded by a spiny collar, numerous cystogenous glands in the body, and having no eyespots., and Longifurcate-pharyngeate distome cercariae (Strigea cercariae) is the cercarial type with a longifurcate tail and a pharynx, both oral and ventral suckers present, the penetration gland cells are all of one kind, the body and furcal finfolds not present, excretory pores located on sides of furcae, and the caudal bodies present in the tailstem. Aside from the cercariae trematodes, a nematode was also observed in an M. maculata sample. The recovered nematodes are characterized by their elongated, cylindrical bodies, typically tapered at both ends, giving them a worm-like appearance (Fig. 2). Prevalence of parasites infection The total prevalence of parasite infection across all sampling sites is 3.78% (95% CI 2.372–5.966), with residential areas harboring the highest infection with 7.89% (95% CI4.21–14.33) prevalence rate, followed by agricultural areas with 3.74% (95% CI 5.39–12.9) prevalence rate while no infection observed in the power plant area. Among freshwater snail species, Radix quadrasi recorded the highest with 40.00% (95% CI 11.76–76.93) prevalence rate, followed by Physella acuta with 18.18 (7.31–38.52), Melanoides maculata with 11.11% (95% CI 5.96–19.79), Sinotia angularis with 3.85% (95% CI 0.68–18.89), and Melanoides tuberculata with 2.27% (95% CI 0.40–11.81) while no infections observed in Pomacea canaliculata, Gyraulus sp., Biomphalaria sp. , and Tarebia granifera. Regarding infection between seasonal periods, only March harbors infection with 6.42% (95% CI 4.04–10.03), and August reported no infections (Table 2 ). Table 2 Prevalence rates of parasite infection per parameter of snails in Balo-i Lake, Balo-i, Lanao del Norte, Philippines. Parameter No. of individuals No. of infected samples Prevalence (%) (CI**) Site 1: Power Plant 122 0 0.00 2: Residential Area 114 9 7.89 (4.21–14.33) 3: Agricultural Area 214 8 3.74 (5.39–12.9) Total 450 17 3.78 (2.372–5.966) Species P. canaliculata 233 0 0.00 S. angularis 26 1 3.85 (0.68–18.89) P. acuta 22 4 18.18 (7.31–38.52) Gyraulus sp. 5 0 0.00 T. granifera 24 0 0.00 Biomphalaria sp. 10 0 0.00 M. maculata 81 9 11.11 (5.96–19.79) M. tuberculata 44 1 2.27 (0.40–11.81) R. quadrasi 5 2 40.00 (11.76–76.93) Month August 185 0 0.00 March 265 17 6.42 (4.04–10.03) **95% Confidence Interval Physicochemical Parameters (pH and Temperature) Physicochemical parameters are among the factors that can affect the prevalence of parasite infection among freshwater snails. In this study, physicochemical parameters (pH and temperature) of the three sampling sites in Balo-i Lake were recorded, with the Power plant area recorded at 6.84 pH in August 2023 while 7.65 pH in March 2024 and 26.5 temperature (°C) in August while 28.4°C in August. Likewise, the Residential area had 7.43 pH in August, 7.33 pH in March, and 26.9°C temperature in August, while 27.6°C as well as Agricultural area recorded 7.75 pH in August while 7.98 pH in March and 27.7°C temperature in August while 29.1°C in March (Table 3 ). The correlation between physicochemical parameters (pH and temperature) and parasite infection of snails in Balo-i Lake was not significant (95% significance level or p = 0.05) given the pH and temperature values in Table 4 , the correlation between parasite infection and pH as well as temperature is technically positive but are too weak. P-values were not significant at p < 0.05 (Table 4 ). Table 3 Physicochemical Parameters (pH and temperature) of the three sampling sites in Balo-i Lake, Balo-i, Lanao del Norte, Philippines. Sampling Sites pH values Temperature (°C) August March August March Power Plant Area 6.84 7.65 26.5 28.4 Residential Area 7.43 7.33 26.9 27.6 Agricultural Area 7.75 7.98 27.7 29.1 Table 4 Correlation between physicochemical parameters (pH and temperature) and parasite infection of snails in Balo-i Lake, Balo-i (95% significance level or p = 0.05). pH Temperature Infection Pearson Correlation 0.505 0.279 Sig. (2-tailed) P-value 0.202 0.645 Discussion The collected freshwater snails were of medical importance as they serve as vectors or an intermediate host for various pathogenic parasites such as nematodes and trematodes. Pomacea canaliculata , on the other hand, was the most abundant species collected and was reported to be an intermediate host of the nematode Angiostrongylus cantonensis , which causes eosinophilic meningitis (Liu et al. 2018 ; Estano, 2023) yet no parasites were observed in the snail samples. This may be attributed to the invasive characteristics of P. canaliculata , wherein they tend to be less susceptible to naturally occurring parasites in a habitat. In addition, they are highly adaptable and were described as having grooming and defense mechanisms, helping them ward off predators and parasites (Cueto, 2015). Still, the total number of samples is not a definitive factor of the presence or absence of parasites among the freshwater snails since other species, such as the R. quadrasi , were shown to be infected despite only having a total of 5 individuals. Species of the genus Radix have been reported to be susceptible to medically and veterinary-important trematodes of bird schistosomes (family Schistosomatidae) and fasciolids (family Fasciolidae) (Huňová et al. 2012 ). M. maculata was found to have the highest number of individuals (9 in total) infected with parasites. This high susceptibility of M. maculata could be influenced by factors such as the presence of the parasite in the habitat, the environmental conditions and habitat type, and the presence of definitive hosts within the area (Paller et al. 2019 ). Co-infection was observed in an M. macluata sample for two cercarial morphotypes. The species of the genus Melanoides , including M. maculata and M. tuberculata , have been reported to accommodate a variety of parasites and varying cercariae morphotypes (Ballesteros and Dela Paz, 2010 ; Paller, 2019; Tujan et al. 2016 ; Najet, 2014; Yousif et al. 2014 ). The associated parasites were also based on morphotype for a more relevant comparison. The data from this study are consistent with the previous literature except for P. acuta . Although associated with several trematode cercarial types, its role as host of the Parapleurolophocercous cercaria is of limited evidence (Frandsen and Christensen, 1984 ). Thus, the presence of this parasite in P. acuta samples provides additional information on the range of parasite morphotypes that this snail species can accommodate. Among the parasites observed, trematodes (cercariae) were the most abundant. Cercarium cercariae is produced by species of the families Monorchiidae, which are intestinal parasites of fish, and Cyclocoelidae, which includes parasites of the respiratory tract of birds. Some of the host species of this type of trematode cercariae include the species of the genera Biomphalaria , Gabbiella , and Lymnaea (Frandsen and Christensen, 1984 ). In this study, the Cercarium cercariae was observed in one individual sample of M. maculata . Previous studies have not recorded Cercarium cercariae as one of the parasites of this snail species. In general, Cercarium cercariae have been an uncommon identification in recent studies as cercariae are usually characterized by a tail used for swimming. Gymnocephalous cercariae is produced by many species, including the family Fasciolidae, which consists of intestinal and liver parasites in herbivorous mammals. It utilizes the snails of the genera Biomphalaria , Bulinus , Ceratophallus , Gabbiella , Gyraulus , Lymnaea , and Melanoides . Among the nine species of the Fasciolidae family, three are responsible for zoonotic infections in humans. Fasciola hepatica and F. gigantica , the liver flukes that cause fascioliasis, and Fasciolopsis buski , the intestinal fluke causing fasciolopsiasis (Siles-Lucas et al. 2020 ). The absence of observed parasites in Gyraulus sp., Biomphalaria sp., and Tarebia granifera , which were recorded to serve as intermediate hosts of pathogenic parasites such as trematodes (El-Ansary and Al-Daihan, 2006 ; Pointier, 2001 ), may have been influenced by the limited number of samples collected and examined. With less than 30 total individuals, these species may have been underrepresented. This cercariae was found to be relatively abundant in M. maculata species. Although it is consistent with the record of Frandsen and Christensen ( 1984 ), it was only found in M. maculata and not in M. tuberclata , which belongs to the same genus, nor in samples of Biomphalaria and Gyraulus sp. previously described to accommodate this cercarial morphotype. Specifically, this cercaria was found in Site 2 (Residential Areas) only, wherein M. maculata was the only snail species collected belonging to the genera previously described to accommodate this cercarial type, suggesting host specificity of parasites. Also, Gymnocephalous cercariae is the most dominant cercarial type and parasite, as it infected six snail individuals. Parapleurolophocercous cercaria develops in rediae and encysts in fish and amphibians. Species of the genera Ceratophallus , Gabbiella , Melanoides , and Pirinella can serve as hosts for this type of parasite, produced by species of the family Heterophyidae, including intestinal parasites of birds and mammals. Within this family, species of Haplorchis (including Haplorchis taichui , H. pumilio , H. yokogawai ) are among those that infect humans in Asia. Adult forms parasitize the small intestines of birds and mammals (birds and humans) and cause abdominal pain, diarrhe, and weight loss (Chai et al. 2023 ). Interestingly, this cercaria was found in samples collected from Sites 2 and 3, the residential and agricultural areas, where toads were observed and where some parts of the lake were used to collect fish. Although it was not the most dominant cercarial type and parasite, it was the type that infected the most snail species – P. acuta , M. maculata , and M. tuberculata . This finding is similar to the results of Paller et al. ( 2019 ), wherein Parapleurolophocercous cercaria was the only cercarial morphotype observed to infect more than one snail species. This implies that Parapleurolophocercous cercaria has low specificity for infection in snail intermediate hosts (Chontananarth and Wongsawad, 2013 ). Echinostome cercariae develop in rediae and encyst in invertebrates, fish, and amphibians. It is produced by species of the family Echinostomatidae consisting of intestinal parasites of birds, reptiles, and mammals. Documented infections are primarily from members of the genera Echinostoma , which causes Echinostomiasis and infects the gastrointestinal tract of humans (Centers for Disease Control and Prevention, 2019 ). While patients are typically asymptomatic, heavy infections can lead to symptoms like abdominal pain, anorexia, nausea, vomiting, diarrhea, and weight loss due to catarrhal inflammation and mild ulceration. This infection is associated with sociocultural practices such as consuming raw or undercooked mollusks and fish (Sah et al. 2018 ). They utilize species of the genera Biomphalaria , Bulinus , Ceratophallus , Gyraulus , Lentorbis , Lymnaea , Pila , and Segmentorbis as intermediate hosts. This study observed two types of Echinostome cercariae in the freshwater snail samples (Fig. 2). Interestingly, these two types were found to infect one host species, the P. acuta . Longifurcate-pharyngeate distome cercariae (Strigea cercariae) develops in sporocysts and encysts in snails, tadpoles, reptiles, and fish. Species of the genera Biomphalaria , Bulinus , Ceratophallus , Gyraulus , Lymnaea , and Melanoides can serve as intermediate hosts of these parasites. They are produced by species of the Strigeidae and Diplostomatidae families, which include various intestinal parasites of birds and mammals. Recorded infections have been documented chiefly from fishes that serve as secondary intermediate hosts and birds (Ondračková et al. 2004 ). This cercaria was observed from R. quadrasi samples, a result consistent with Martin I and Cabrera (2018), who reported Lymnea (Radix) quadrasi from ricefields in Batangas, Philippines, to be infected with the Strigea cercariae parasite. Nematode also was recovered in snails in this study. Generally, nematodes adopt either a free-living or a parasitic lifestyle. Parasitic nematodes include heartworms that infect domestic dogs, hookworms, and pinworms that commonly infect small children. The nematode observed in this study was found in M. maculata , which was recorded to be one of the hosts of the nematode Angiostrongylus cantonensis that causes eosinophilic meningitis (Tujan et al. 2016 ). In addition, it was found in Site 2 or near the residential areas. This could pose a threat to the people, especially the children living near the lake who are exposed to the waters where such parasites could be present. However, this record is insufficient, given that only one individual sample was recorded to have nematode infection. Prevalence Rates of Parasite Infection The total prevalence of parasite infection across all sampling sites is 3.78% (95% CI 2.372–5.966), a value higher than documented by Paller et al. ( 2019 ) on the cercarial fauna of freshwater snails (n = 2720) of agricultural areas in Laguna, Philippines with only 1.56% total prevalence rate. However, the present study has a lower prevalence rate than the 30.53% total prevalence of parasite infection recorded by Logronio et al. ( 2020 ) in freshwater snails (n = 2460) from the Municipalities of Lala, Kapatagan, and Salvador, Lanao del Norte. It should be noted, however, that they included free-living protozoa (Paramecium) to calculate this prevalence, which may have affected the calculated value. Still, other studies also show a higher total infection prevalence. Chontananarth and Wongsawad ( 2013 ) reported a 17.27% total prevalence of trematodes in freshwater snails (n = 2779) from Chiang Mai province, Thailand while Selbach et al. ( 2020 ) recorded an overall prevalence of 19.6% of primarily trematode infection among freshwater snails (families Lymnaeidae and Planorbidae; n = 5347) in five lakes in Ruhr River system in Germany. A stark difference between this study and those previously reported is the gap between the total number of samples. Nevertheless, recording five cercarial morphotypes and a nematode from the relatively small sample size implies that the Balo-i Lake could also harbor abundant snail and parasite composition. Among the parasites observed and identified, the Gymnocephalous cercaria had the highest prevalence with 1.33% (95% CI 0.61–2.88), followed by Parapleurolophocercous cercaria with 1.11% (95% CI 0.48–2.57) (Table 5 ). Although the relative dominance of Parapleurolophocercous cercaria infection among freshwater snails has been documented by previous studies (Chontananarth and Wongsawad, 2013 ; Anucherngchai et al. 2016 ), studies that documented Gymnocephalous cercaria from freshwater snails recorded low prevalence (Chontananarth and Wongsawad, 2013 ). Table 5 Prevalence of parasite infection per parasite across the three sampling sites, Balo-i Lake, Balo-i, Lanao del Norte, Philippines. Parasite Power Plant Area Residential Area Agricultural Area Total Prevalence (%) (CI**) No. of infected samples and Prevalence (%) No. of infected samples Prevalence (%) No. of infected samples Prevalence (%) Trematode Cer - 1 0.88 - - 0.22 (0.04–1.25) Par - 2 1.75 3 1.40 1.11 (0.48–2.57) Gym - 6 5.26 - - 1.33 (0.61–2.88) Ech - - - 2 0.93 0.44 (0.12–1.61) Str - - - 2 0.93 0.44 (0.12–1.61) Non-trematode Nematode - 1 0.88 - - 0.22 (0.04–1.25) **95% Confidence Interval Cer: Cercarium cercaraie, Par: Parapleurolophocercous cercaria, Gym: Gymnocephalous cercariae, Ech: Echinostome cercariae, and Str: Strigea cercariae. Still, the findings in this study are similar to those reported by Phiri et al. ( 2007 ), wherein Gymnocephalous cercaria was also the most common cercarial type observed from snail samples of the Kafue wetlands of Zambia. Interestingly, the Kafue River within this wetland is utilized for the generation of electricity, similar to how water flowing into Balo-i Lake is used by Agus IV to generate electricity. The prevalence rates among sampling sites showed that Site 2 (Residential Area) had the highest prevalence rate with 7.89% (95% CI 4.21–14.33), followed by Site 3 (Agricultural Area) with 3.74% (95% CI 5.39–12.9). In contrast, Site 1 (Power Plant) had no infected samples. These results can be attributed to the difference in the characteristics of each sampling site. In the Power Plant area, the presence of the riprap wall with connecting roads represents habitat modification, which is a significant threat to biodiversity (World Wide Fund for Nature, 2020 ). Marcogliese ( 2023 ) reported that multi-host parasites, particularly those with complex life cycles and free-living infectious stages such as the trematodes and nematodes, should be affected by changes in biodiversity more than directly transmitted specialists. Thus, the parasites that use snails as intermediate hosts cannot accomplish their life cycles since not many final hosts exist within the area. According to Jayawardena et al. ( 2010 ), the diversity of digenean trematodes is dependent on conditions that are conducive to transmission, such as the presence of final and intermediate hosts. Thus, although some birds were observed flying around this site, the type of parasites that could thrive in the area is limited. On the other hand, the site near residential areas (Site 2) had a ground area with trees and frequent human activities like washing clothes. In addition, near this area is a small isolated or caged area most likely placed for fish collection. Ducks were sighted swimming around, and amphibians were also observed while collecting snails on this site. Pollution was evident in this site as many plastic and waste materials were observed floating and scattered around. The last site, Site 3, was near agricultural areas with an open grassland area directly adjacent to the lake, and grazing animals like cows could be seen. Large birds were seen flying over while ducks were swimming, and many insects, including dragonflies, were flying across small flowering plants. Human activities were also present, as people doing their laundry were seen in the area. Anthropogenic activities such as open field defecation, urination, livestock grazing, farming, and swimming were highly correlated with trematode infection (Mereta et al. 2019 ). Prevalence among species was highest for R. quadrasi with 40% (95% CI 11.76–76.93), a value which may have been influenced by its very small sample size (n = 5) as well as the susceptibility of R. quadrasi to parasite infection, along with other species from the same genus (Soldánová et al. 2010 ; Huňová et al. 2012 ; Martin I and Cabrera, 2018) and family (Correa et al. 2010). Meanwhile, M. tuberculata has the lowest prevalence rate with 2.27% (95% CI 0.40–11.81) despite being a species with many published studies documenting it harboring different parasites (Ballesteros and Dela Paz, 2010 ; Tujan et al. 2016 ; Najet, 2014; Yousif et al. 2014 ). Physicochemical parameters are among the factors that can affect the prevalence of parasite infection among freshwater snails. In this study, physicochemical parameters (pH and temperature) of the three sampling sites in Balo-i Lake were recorded, with the Power plant area recorded at 6.84 pH in August 2023 while 7.65 pH in the month of March 2024 and 26.5 temperature (°C) in August while 28.4°C in August. Likewise, the Residential area had 7.43 pH in August, 7.33 pH in March, and 26.9°C temperature in August, while 27.6°C as well as Agricultural area recorded 7.75 pH in August while 7.98 pH in March and 27.7°C temperature in August while 29.1°C in March. As described in the previous section, increased temperature generally increases the prevalence. In terms of pH, Logronio ( 2020 ) described that pH and infected snails showed a negative correlation and a positive correlation to non-infected, supported by further regression analysis. The prevalence of parasite infection was 0% in August or the wet season, while 6.42% was in March or the dry season. This difference can be attributed to the seasonal changes in rainfall, temperature, and food availability that can affect the intensity or prevalence of parasitism through changes in host susceptibility (Shearer and Ezenwa, 2020 ), or changes in host exposure influenced by seasonal variation in host behavior (Petrić et al. 2011 ) or parasite development and survival (Zamora-Vilchis et al. 2012 ). Despite these mechanisms, all findings suggest a strong and positive association between parasite prevalence and temperature. Parasite prevalence increased during the dry season, as observed from parasite-host interactions of helminths and many host species, including fishes, mammals, and birds (Shearer and Ezenwa, 2020 ; Zamora-Vilchis et al. 2012 ). Thus, the data for the parasites observed during the August sampling must be lower than during the March sampling. This is consistent with the findings of Purwaningsih et al. ( 2022 ), wherein the highest prevalence of Fasciola gigantica , a trematode, infection in Lymnaea sp. snails was highest in November when the rainfall was low, and was lowest in April when the recorded rainfall was at its peak. Also, the study by Rowel et al. ( 2015 ) showed that the cercarial shedding of snails ( Biomphalaria ) has a positive relationship with temperature and a negative relationship with pH. In this study, however, given the pH and temperature values in Table 4 , the correlation between parasite infection and pH and temperature is technically positive but is too weak. P-values were not significant at p < 0.05. These inconsistent results imply that the seasonal difference in the prevalence of infection may have been influenced more by rainfall patterns and indirect changes in the host and environmental conditions instead of the temperature and pH levels. Human activities and disturbances could also be a factor in altering water flow patterns, changing the habitat structure, and disrupting the life cycle of some parasite species. Other studies that explored the shedding of cercariae by freshwater snail species showed a non-linear relationship between pH and temperature and the cercarial emergence. It was instead a range of optimum pH and temperature levels (20–25°C for monostome type and 25–30°C for Pleurolophocercous cercariae ) that induced cercarial shedding (Achiorno and Martorelli, 2016 ). The presence of documented parasites, including trematodes and nematodes, suggests the presence and abundance of vertebrate definitive and intermediate hosts needed to complete their life cycle. This indicates that the community, especially sites 2 and 3, the residential and agricultural areas, still have birds, fishes, reptiles, and mammals that are thriving and helping support the parasite population to persist. However, the presence of these parasites also has implications for public health and veterinary medicine concerning the risk they pose to the animals and humans living near and around Balo-i Lake. Most of the parasites observed are cercarial morphotypes produced by pathogenic groups, including intestinal parasites of fish, birds, and mammals. The prevalence of parasitic zoonoses, facilitated by freshwater snails acting as intermediate hosts, has increased human mortality and morbidity as these snails are utilized for food and medicinal purposes (Logronio, 2020 ). Although parasites, in general, are essential in keeping the balance in an ecosystem, human disturbances and alterations can tweak this balance, causing harmful effects and diseases to humans. With freshwater snails as a point of transmission, it is essential that control measures, including proper sanitation and possibly managing parasite hosts, be in place to prevent, manage, and control diseases (Pathak, et al. 2023 ). These measures aim to mitigate the transmission of diseases and reduce their impact on human and animal populations. Johnson et al. ( 2009 ) emphasized the importance of collaboration of ecological and parasitological research in the mediation of transmission of human pathogens as their findings showed that increased community diversity reduced Schistosoma infection among snail hosts ( Biomphalaria glabrata ) by 20–50%. Thus, maintaining a diverse and healthy ecosystem can be a way to control and mitigate disease transmission by parasites. Conclusion and Recommendation The presence of parasites in Balo-i Lake has implications for public health and veterinary medicine, particularly for communities close to the lake. Control measures, including proper sanitation and management of parasite hosts, are crucial for preventing and managing disease transmission. Maintaining a diverse and healthy ecosystem may help mitigate disease transmission by reducing host susceptibility to infection. Future studies in the lake include more sampling days and time and other areas around the lake for more comprehensive results; molecular analysis can be utilized to identify parasites to provide more insight into their composition, abundance, and implications for the people and animals surrounding the lake. Regular surveillance of parasite infections in freshwater snails is in place to detect changes in prevalence rates and understand parasite dynamics to aid public health. Community engagement and education programs are implemented to raise awareness of the health risks associated with parasite infections and to promote practices that reduce exposure. Efforts to preserve and restore the ecological integrity of the lake and its surrounding habitats are made to maintain a healthy ecosystem and reduce the risk of disease transmission. Through these recommendations and adopting a holistic approach to parasite control, we can work towards safeguarding the health and well-being of communities living near Balo-i Lake and preserving the ecological balance of this freshwater ecosystem. Declarations Compliance with ethical standards Conflict of interest None declared Author contribution Conceived and designed sampling: JDB, LJGM, and LAE performed the collection of samples and laboratory analysis as well as the writing of the paper. Acknowledgments The author would like to express the most profound appreciation and gratitude to the local government units (LGU) and locals of Nangka, Balo-i, Lanao del Norte, for assistance during the collection of samples and to the Department of Biological Sciences, College of Science and Mathematics, Center for Biodiversity Studies and Conservation of Premier Research Institute of Science and Mathematics for allowing the researcher to conduct the processing of samples and laboratory analysis. To the Agus IV Hydroelectric Power Plant Management and the Department of Science and Technology-Science Education Institute for funding this research. References Achiorno CL, Martorelli SR (2016) Effect of temperature changes on the cercarial-shedding rate of two trematodes. 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PLoS ONE 7(6):e39208. https://doi.org/10.1371/journal.pone.0039208 Cite Share Download PDF Status: Published Journal Publication published 26 Feb, 2026 Read the published version in Journal of Parasitic Diseases → Version 1 posted Reviewers agreed at journal 14 Jul, 2025 Editor invited by journal 13 Jul, 2025 Reviewers invited by journal 14 Aug, 2024 Editor assigned by journal 10 Aug, 2024 First submitted to journal 10 Aug, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4891076","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":340376717,"identity":"75d6a4f4-a6a1-4c8d-a453-816198e99ed7","order_by":0,"name":"LEONARDO A. 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Estaño","email":"","orcid":"","institution":"Mindanao State University - Iligan Institute of Technology: MSU-Iligan Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Leonardo","middleName":"A.","lastName":"Estaño","suffix":""}],"badges":[],"createdAt":"2024-08-10 09:38:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4891076/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4891076/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s12639-026-01920-9","type":"published","date":"2026-02-26T15:58:45+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":64282599,"identity":"a7db61ca-8c64-4c3e-92da-780e1779c32b","added_by":"auto","created_at":"2024-09-11 08:02:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":957026,"visible":true,"origin":"","legend":"\u003cp\u003eMap of the Study Sites in Balo-i Lake, Balo-i, Lanao del Norte Province, Philippines.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4891076/v1/2ea94164875e090c3d1e7097.png"},{"id":64282598,"identity":"c0497422-6752-4d28-b452-fbfb2160b7e5","added_by":"auto","created_at":"2024-09-11 08:02:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1518110,"visible":true,"origin":"","legend":"\u003cp\u003eParasites observed from freshwater snails of Balo-i Lake viewed under microscope (HPO lens). \u003cem\u003eCercarium cercariae \u003c/em\u003e(A-B), \u003cem\u003eGymnocephalous cercariae\u003c/em\u003e (C), \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e (D), \u003cem\u003eEchinostome cercariae\u003c/em\u003e (E-F), \u003cem\u003eEchinostome cercariae\u003c/em\u003e types occurring within a single snail host (G), \u003cem\u003eStrigea cercariae\u003c/em\u003e (H), and Nematode (I). (Scale bar = 20μM)\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4891076/v1/df106550bf614d4f65ccb9b0.png"},{"id":103765587,"identity":"e0b06709-5319-48b6-a7aa-0480d5ac9191","added_by":"auto","created_at":"2026-03-02 16:05:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3334201,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4891076/v1/a277f6c1-b1e4-4f21-a207-2a0893559a5c.pdf"}],"financialInterests":"","formattedTitle":"Prevalence of parasites in freshwater snails with notes on helminth-associated diseases in Balo-i Lake, Lanao del Norte, Philippines","fulltext":[{"header":"Introduction","content":"\u003cp\u003eFreshwater snails have been widely explored for their role as intermediate host of infectious trematodes and other parasites of animals and humans (Paller et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Martin and Cabrera, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Logronio et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Cawas et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Esta\u0026ntilde;o, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Some are responsible for several important human diseases such as schistosomiasis (bloodflukes) and fasciolosis (liver flukes) (Vaughn, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Jumawan and Esta\u0026ntilde;o, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Millions of people in about 90 countries suffer from parasitic diseases transmitted by intermediate hosts freshwater snails. For instance, more than 20\u0026nbsp;million people are infected with \u003cem\u003eFasciola hepatica\u003c/em\u003e, and more than 200\u0026nbsp;million people are infected with \u003cem\u003eSchistosoma\u003c/em\u003e spp. (Correa et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Shan et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Skelly and Da'Dara, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Infections pose a public health risk and cause severe socio-economic problems in many tropical and subtropical countries, including the Philippines (Prasopdee et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Esta\u0026ntilde;o and Jumawan, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBalo-i Lake is an artificial lake in the Municipality of Balo-i, Lanao del Norte in the Philippines, that feeds from the larger Lake Lanao in Lanao del Sur through the Agus River. This freshwater ecosystem harbors aquatic plants and animals that support its biodiversity and various livelihoods to the community. It has been a water source for the nearby locals for washing clothes and other domestic use, collecting fish, shrimps, and edible snails (Demayo et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). However, there is a dearth of information on freshwater snails and their associated parasites in the country, and no study has been conducted in the area. This study provides valuable information and updates on the resource utilization of freshwater snails in the different habitats surrounding the lake and the possible diseases associated with these freshwater snails.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eThe locale of the study\u003c/h2\u003e \u003cp\u003eThe study site, Balo-i Lake (8\u0026deg; 7' 44.7594\" N, 124\u0026deg; 12' 1.8\" E), is situated in the Municipality of Balo-i, Lanao del Norte. Surrounding the lake are Barangays Nangka, Maria Cristina, Matampay, and Somiorang wherein existing land uses include built-up areas and agriculture (National Power Corporation, 2021). Balo-i Lake is a man-made lake that is part of the Lake Lanao watershed, serving as the reservoir of the Agus IV Hydroelectric Power Plant that is host to three generating units. Balo-i Lake is fed by water flowing from Lake Lanao in Lanao del Sur through the Agus River, which spans 36.5 kilometers (22.7 mi) from Lanao Lake to Iligan Bay. Within the lake, there is a significant accumulation of water hyacinth (\u003cem\u003eEichhornia crassipes\u003c/em\u003e) that continues to persist. Three sampling sites were established along the littoral/riparian zone of Balo-i Lake (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003eSampling Methods\u003c/h2\u003e \u003cp\u003eBefore the collection of samples, necessary permits were acquired from the LGU of Balo-i, and owners of the areas included in the sampling sites were also asked for their permission. Three sampling sites were identified and established namely; Power Plant area, Residential area, and Agricultural area.\u003c/p\u003e \u003cp\u003eSampling site 1 is along the Agus IV Power Plant area (8\u0026deg; 8' 1.017\" N, 124\u0026deg; 12' 2.0334\" E) thereby it is directly connected to the lake by a riprap wall, serving as the border to where the Agus IV facilities were located. Vegetation is limited, with few grasses, vines, and shrubs. Animals such as birds, insects, and shrimp were also present. The second site was established near residential areas (8\u0026deg; 7' 40.7\" N, 124\u0026deg; 12' 28.2\" E) where vegetation was more abundant, aside from grasses and vines, ferns, herbaceous plants like taro and banana, and trees were present. Animals such as ducks, insects, amphibians, as well as terrestrial snails were observed in this area. Also, a small fish pond was seen within the site. The third sampling site was near agricultural area (6\u0026deg; 7' 09.1\" N, 124\u0026deg; 11' 58.2\" E), particularly an openland with abundant coconut trees. Found directly on the lake and lake shore were plants such as \u003cem\u003eLantana camara\u003c/em\u003e, some vines, shrubs, and even a guava tree, as well as animals including ducks, birds, and insects. Livestock mammals such as cows were observed within the area. In all of these sites, the dense water hyacinths in the lake were prominent and pollution were evident, especially in the residential area and Power Plant area.\u003c/p\u003e \u003cp\u003eIn each sampling site, a belt transect of 100 m in length with a 1 m line perpendicular on both sides of the main transect was established. The collection of snails was done by handpicking along the belt transect lines. Sampling was performed between 6:00 am to 10:00 am. Snail samples collected were placed in containers with lake water, and transported to the laboratory within 2\u0026ndash;3 hours after collection. Sampling was done twice, on August, 2023 and March, 2024.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eProcessing and identification samples\u003c/h2\u003e \u003cp\u003eEach sample was recorded and identified to species level using taxonomic keys, different references, web searches, and previously published studies. Identification guides by Frest and Johannes (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1999\u003c/span\u003e), Harold and Guralnick (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), Cummings and Lydeard (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) were utilized. To assess parasite infection in the samples, each snail was subjected to the crushing method (Caron et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Jumawan and Esta\u0026ntilde;o, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) wherein the snails were crushed using mortar and pestle and added few drops of saline solution. Using a dropper, 2\u0026ndash;3 drops of the resulting liquid were placed onto a glass slide and viewed using a compound microscope to observe for parasites. Smaller snail samples, with sizes about 1cm or less, were directly crushed using two glass slides and viewed under a microscope.\u003c/p\u003e \u003cp\u003eAll parasites detected were identified based on morphotype using the classification key and identification manuals of Frandsen and Christensen (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e), Chontananarth and Wongsawad (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), Farahnak, et al. (2006), Van Wyk and Mayhew (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), Mohammed, et al. (2015), and Chontananarth, et al. (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Only presence-absence data of parasites were identified in the present study, that is the prevalence of infection or the proportion of infected individuals.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003eMeasurement of pH and temperature\u003c/h2\u003e \u003cp\u003eThe physicochemical parameter pH was measured \u003cem\u003ein situ\u003c/em\u003e using a multi-tester for every sampling site to study their possible effects on parasite prevalence among freshwater snails.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eData Analysis\u003c/h2\u003e \u003cp\u003eThe prevalence of parasite infection was computed using the formula:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:Prevalence=\\frac{\\#\\:\\text{o}\\text{f}\\:\\text{i}\\text{n}\\text{f}\\text{e}\\text{c}\\text{t}\\text{e}\\text{d}\\:\\text{s}\\text{a}\\text{m}\\text{p}\\text{l}\\text{e}\\text{s}}{\\text{t}\\text{o}\\text{t}\\text{a}\\text{l}\\:\\text{n}\\text{u}\\text{m}\\text{b}\\text{e}\\text{r}\\:\\text{o}\\text{f}\\:\\text{s}\\text{a}\\text{m}\\text{p}\\text{l}\\text{e}\\text{s}}x\\:100\\%$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eA 95% confidence level was applied to the prevalence using the OpenEpi Program. Pearson\u0026rsquo;s correlation coefficient analysis was used to determine the correlation between physicochemical parameters and parasite infection prevalence. Statistical analysis was done using the SPSS version 20.0 software.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eFreshwater snail collected\u003c/h2\u003e \u003cp\u003eFour hundred fifty snail samples belonging to 9 species were examined for parasite infection. These include \u003cem\u003ePomacea canaliculata\u003c/em\u003e (233) known as an agricultural pest in the ricefield; Sinotaia \u003cem\u003eangularis\u003c/em\u003e (26), an edible snail; Tarebia \u003cem\u003egranifera\u003c/em\u003e (24); \u003cem\u003eMelanoides tuberculata\u003c/em\u003e (44), \u003cem\u003eMelanoides maculata\u003c/em\u003e (81), \u003cem\u003eRadix quadrasi\u003c/em\u003e (5), \u003cem\u003eGyraulus\u003c/em\u003e sp. (5) \u003cem\u003eBiomphalaria\u003c/em\u003e sp. (10) and \u003cem\u003ePhysella acuta\u003c/em\u003e (22). One hundred eighty-five individuals were collected from the August 2023 sampling, while 265 individuals were from the March 2024 sampling. All these freshwater snail species were of medical importance as they serve as vectors or an intermediate host for various pathogenic parasites such as nematodes and trematodes (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\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\u003eHost species and prevalence of parasites in snails of Balo-i Lake, Balo-i, Lanao del Norte, Philippines.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" 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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eHost Snail Species\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNo. of samples examined\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c8\" namest=\"c3\"\u003e \u003cp\u003eNumber of infected individuals\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eTotal Prevalence (%) (CI**)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCer\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePar\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGym\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eEch\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eStr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNematode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eP. canaliculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e233\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\u003e-\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eS. angularis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e26\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\u003e-\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3.85 (0.68\u0026ndash;18.89)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eP. acuta\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e22\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\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e18.18 (7.31\u0026ndash;38.52)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eGyraulus sp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\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\u003e-\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eT. granifera\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e24\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\u003e-\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eBiomphalaria sp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10\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\u003e-\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. maculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e11.11 (5.96\u0026ndash;19.79)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. tuberculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e44\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\u003e1\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.27 (0.40-11.81)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eR. quadrasi\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\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\u003e-\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e40.00 (11.76\u0026ndash;76.93)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u003cem\u003e**95% Confidence Interval\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u003cem\u003eCer: Cercarium cercaraie, Par: Parapleurolophocercous cercaria, Gym: Gymnocephalous cercariae, Ech: Echinostome cercariae, and Str: Strigea cercariae.\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eParasites recovered in freshwater snails\u003c/h2\u003e \u003cp\u003eA total of 5 parasite morphotypes were identified: Cercarium cercariae is a cercarial type characterized by the absence of tail/s. It develops in rediae and encyst in snails. Gymnocephalous cercariae is the cercarial type characterized by an unforked tail, the presence of a ventral sucker on the mid-ventral surface of the body, neither stylet nor spiny collar present, having no eyespots, and numerous cystogenous glands in the body. They develop in rediae and encyst on external substrates. Parapleurolophocercous cercaria is a cercarial type characterized by an unforked tail with well-developed fin folds, ventral sucker vestigial or absent, visible eyespots, and a few cystogenous glands in the body. Echinostome cercariae are characterized by having an unforked tail, a ventral sucker on the mid-ventral surface of the body, an oral sucker without a stylet but are surrounded by a spiny collar, numerous cystogenous glands in the body, and having no eyespots., and Longifurcate-pharyngeate distome cercariae (Strigea cercariae) is the cercarial type with a longifurcate tail and a pharynx, both oral and ventral suckers present, the penetration gland cells are all of one kind, the body and furcal finfolds not present, excretory pores located on sides of furcae, and the caudal bodies present in the tailstem. Aside from the cercariae trematodes, a nematode was also observed in an \u003cem\u003eM. maculata\u003c/em\u003e sample. The recovered nematodes are characterized by their elongated, cylindrical bodies, typically tapered at both ends, giving them a worm-like appearance (Fig.\u0026nbsp;2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePrevalence of parasites infection\u003c/h2\u003e \u003cp\u003eThe total prevalence of parasite infection across all sampling sites is 3.78% (95% CI 2.372\u0026ndash;5.966), with residential areas harboring the highest infection with 7.89% (95% CI4.21\u0026ndash;14.33) prevalence rate, followed by agricultural areas with 3.74% (95% CI 5.39\u0026ndash;12.9) prevalence rate while no infection observed in the power plant area. Among freshwater snail species, \u003cem\u003eRadix quadrasi\u003c/em\u003e recorded the highest with 40.00% (95% CI 11.76\u0026ndash;76.93) prevalence rate, followed by \u003cem\u003ePhysella acuta\u003c/em\u003e with 18.18 (7.31\u0026ndash;38.52), \u003cem\u003eMelanoides maculata\u003c/em\u003e with 11.11% (95% CI 5.96\u0026ndash;19.79), \u003cem\u003eSinotia angularis\u003c/em\u003e with 3.85% (95% CI 0.68\u0026ndash;18.89), and \u003cem\u003eMelanoides tuberculata\u003c/em\u003e with 2.27% (95% CI 0.40\u0026ndash;11.81) while no infections observed in \u003cem\u003ePomacea canaliculata, Gyraulus\u003c/em\u003e sp., \u003cem\u003eBiomphalaria sp.\u003c/em\u003e, and \u003cem\u003eTarebia granifera.\u003c/em\u003e Regarding infection between seasonal periods, only March harbors infection with 6.42% (95% CI 4.04\u0026ndash;10.03), and August reported no infections (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\u003ePrevalence rates of parasite infection per parameter of snails in Balo-i Lake, Balo-i, Lanao del Norte, Philippines.\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\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo. of individuals\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo. of infected samples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePrevalence (%) (CI**)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSite\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\u003e1: Power Plant\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2: Residential Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e114\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.89 (4.21\u0026ndash;14.33)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3: Agricultural Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e214\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.74 (5.39\u0026ndash;12.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e3.78 (2.372\u0026ndash;5.966)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSpecies\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eP. canaliculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eS. angularis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.85 (0.68\u0026ndash;18.89)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eP. acuta\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.18 (7.31\u0026ndash;38.52)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eGyraulus sp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eT. granifera\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eBiomphalaria sp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. maculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.11 (5.96\u0026ndash;19.79)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. tuberculata\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.27 (0.40\u0026ndash;11.81)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eR. quadrasi\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40.00 (11.76\u0026ndash;76.93)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMonth\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAugust\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMarch\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e265\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.42 (4.04\u0026ndash;10.03)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u003cem\u003e**95% Confidence Interval\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003ePhysicochemical Parameters (pH and Temperature)\u003c/h2\u003e \u003cp\u003ePhysicochemical parameters are among the factors that can affect the prevalence of parasite infection among freshwater snails. In this study, physicochemical parameters (pH and temperature) of the three sampling sites in Balo-i Lake were recorded, with the Power plant area recorded at 6.84 pH in August 2023 while 7.65 pH in March 2024 and 26.5 temperature (\u0026deg;C) in August while 28.4\u0026deg;C in August. Likewise, the Residential area had 7.43 pH in August, 7.33 pH in March, and 26.9\u0026deg;C temperature in August, while 27.6\u0026deg;C as well as Agricultural area recorded 7.75 pH in August while 7.98 pH in March and 27.7\u0026deg;C temperature in August while 29.1\u0026deg;C in March (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The correlation between physicochemical parameters (pH and temperature) and parasite infection of snails in Balo-i Lake was not significant (95% significance level or p\u0026thinsp;=\u0026thinsp;0.05) given the pH and temperature values in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the correlation between parasite infection and pH as well as temperature is technically positive but are too weak. P-values were not significant at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\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\u003ePhysicochemical Parameters (pH and temperature) of the three sampling sites in Balo-i Lake, Balo-i, Lanao del Norte, Philippines.\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSampling Sites\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003epH values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTemperature (\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAugust\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMarch\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAugust\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMarch\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePower Plant Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e26.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResidential Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e26.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e27.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAgricultural Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e29.1\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\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\u003eCorrelation between physicochemical parameters (pH and temperature) and parasite infection of snails in Balo-i Lake, Balo-i (95% significance level or p\u0026thinsp;=\u0026thinsp;0.05).\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTemperature\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInfection\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePearson Correlation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.505\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.279\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 \u003cp\u003eSig. (2-tailed) P-value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.202\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.645\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"},{"header":"Discussion","content":"\u003cp\u003eThe collected freshwater snails were of medical importance as they serve as vectors or an intermediate host for various pathogenic parasites such as nematodes and trematodes. \u003cem\u003ePomacea canaliculata\u003c/em\u003e, on the other hand, was the most abundant species collected and was reported to be an intermediate host of the nematode \u003cem\u003eAngiostrongylus cantonensis\u003c/em\u003e, which causes eosinophilic meningitis (Liu et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Estano, 2023) yet no parasites were observed in the snail samples. This may be attributed to the invasive characteristics of \u003cem\u003eP. canaliculata\u003c/em\u003e, wherein they tend to be less susceptible to naturally occurring parasites in a habitat. In addition, they are highly adaptable and were described as having grooming and defense mechanisms, helping them ward off predators and parasites (Cueto, 2015). Still, the total number of samples is not a definitive factor of the presence or absence of parasites among the freshwater snails since other species, such as the \u003cem\u003eR. quadrasi\u003c/em\u003e, were shown to be infected despite only having a total of 5 individuals. Species of the genus \u003cem\u003eRadix\u003c/em\u003e have been reported to be susceptible to medically and veterinary-important trematodes of bird schistosomes (family Schistosomatidae) and fasciolids (family Fasciolidae) (Huňov\u0026aacute; et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). \u003cem\u003eM. maculata\u003c/em\u003e was found to have the highest number of individuals (9 in total) infected with parasites. This high susceptibility of \u003cem\u003eM. maculata\u003c/em\u003e could be influenced by factors such as the presence of the parasite in the habitat, the environmental conditions and habitat type, and the presence of definitive hosts within the area (Paller et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Co-infection was observed in an \u003cem\u003eM. macluata\u003c/em\u003e sample for two cercarial morphotypes. The species of the genus \u003cem\u003eMelanoides\u003c/em\u003e, including \u003cem\u003eM. maculata\u003c/em\u003e and \u003cem\u003eM. tuberculata\u003c/em\u003e, have been reported to accommodate a variety of parasites and varying cercariae morphotypes (Ballesteros and Dela Paz, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Paller, 2019; Tujan et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Najet, 2014; Yousif et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe associated parasites were also based on morphotype for a more relevant comparison. The data from this study are consistent with the previous literature except for \u003cem\u003eP. acuta\u003c/em\u003e. Although associated with several trematode cercarial types, its role as host of the \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e is of limited evidence (Frandsen and Christensen, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Thus, the presence of this parasite in \u003cem\u003eP. acuta\u003c/em\u003e samples provides additional information on the range of parasite morphotypes that this snail species can accommodate. Among the parasites observed, trematodes (cercariae) were the most abundant.\u003c/p\u003e \u003cp\u003e \u003cem\u003eCercarium cercariae\u003c/em\u003e is produced by species of the families Monorchiidae, which are intestinal parasites of fish, and Cyclocoelidae, which includes parasites of the respiratory tract of birds. Some of the host species of this type of trematode cercariae include the species of the genera \u003cem\u003eBiomphalaria\u003c/em\u003e, \u003cem\u003eGabbiella\u003c/em\u003e, and \u003cem\u003eLymnaea\u003c/em\u003e (Frandsen and Christensen, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). In this study, the \u003cem\u003eCercarium cercariae\u003c/em\u003e was observed in one individual sample of \u003cem\u003eM. maculata\u003c/em\u003e. Previous studies have not recorded \u003cem\u003eCercarium cercariae\u003c/em\u003e as one of the parasites of this snail species. In general, \u003cem\u003eCercarium cercariae\u003c/em\u003e have been an uncommon identification in recent studies as cercariae are usually characterized by a tail used for swimming. \u003cem\u003eGymnocephalous cercariae\u003c/em\u003e is produced by many species, including the family Fasciolidae, which consists of intestinal and liver parasites in herbivorous mammals. It utilizes the snails of the genera \u003cem\u003eBiomphalaria\u003c/em\u003e, \u003cem\u003eBulinus\u003c/em\u003e, \u003cem\u003eCeratophallus\u003c/em\u003e, \u003cem\u003eGabbiella\u003c/em\u003e, \u003cem\u003eGyraulus\u003c/em\u003e, \u003cem\u003eLymnaea\u003c/em\u003e, and \u003cem\u003eMelanoides\u003c/em\u003e. Among the nine species of the Fasciolidae family, three are responsible for zoonotic infections in humans. \u003cem\u003eFasciola hepatica\u003c/em\u003e and \u003cem\u003eF. gigantica\u003c/em\u003e, the liver flukes that cause fascioliasis, and \u003cem\u003eFasciolopsis buski\u003c/em\u003e, the intestinal fluke causing fasciolopsiasis (Siles-Lucas et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe absence of observed parasites in \u003cem\u003eGyraulus\u003c/em\u003e sp., \u003cem\u003eBiomphalaria\u003c/em\u003e sp., and \u003cem\u003eTarebia granifera\u003c/em\u003e, which were recorded to serve as intermediate hosts of pathogenic parasites such as trematodes (El-Ansary and Al-Daihan, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Pointier, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2001\u003c/span\u003e), may have been influenced by the limited number of samples collected and examined. With less than 30 total individuals, these species may have been underrepresented.\u003c/p\u003e \u003cp\u003eThis cercariae was found to be relatively abundant in \u003cem\u003eM. maculata\u003c/em\u003e species. Although it is consistent with the record of Frandsen and Christensen (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e), it was only found in \u003cem\u003eM. maculata\u003c/em\u003e and not in \u003cem\u003eM. tuberclata\u003c/em\u003e, which belongs to the same genus, nor in samples of \u003cem\u003eBiomphalaria\u003c/em\u003e and \u003cem\u003eGyraulus\u003c/em\u003e sp. previously described to accommodate this cercarial morphotype. Specifically, this cercaria was found in Site 2 (Residential Areas) only, wherein \u003cem\u003eM. maculata\u003c/em\u003e was the only snail species collected belonging to the genera previously described to accommodate this cercarial type, suggesting host specificity of parasites. Also, \u003cem\u003eGymnocephalous cercariae\u003c/em\u003e is the most dominant cercarial type and parasite, as it infected six snail individuals.\u003c/p\u003e \u003cp\u003e \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e develops in rediae and encysts in fish and amphibians. Species of the genera \u003cem\u003eCeratophallus\u003c/em\u003e, \u003cem\u003eGabbiella\u003c/em\u003e, \u003cem\u003eMelanoides\u003c/em\u003e, and \u003cem\u003ePirinella\u003c/em\u003e can serve as hosts for this type of parasite, produced by species of the family Heterophyidae, including intestinal parasites of birds and mammals. Within this family, species of \u003cem\u003eHaplorchis\u003c/em\u003e (including \u003cem\u003eHaplorchis taichui\u003c/em\u003e, \u003cem\u003eH. pumilio\u003c/em\u003e, \u003cem\u003eH. yokogawai\u003c/em\u003e) are among those that infect humans in Asia. Adult forms parasitize the small intestines of birds and mammals (birds and humans) and cause abdominal pain, diarrhe, and weight loss (Chai et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Interestingly, this cercaria was found in samples collected from Sites 2 and 3, the residential and agricultural areas, where toads were observed and where some parts of the lake were used to collect fish. Although it was not the most dominant cercarial type and parasite, it was the type that infected the most snail species \u0026ndash; \u003cem\u003eP. acuta\u003c/em\u003e, \u003cem\u003eM. maculata\u003c/em\u003e, and \u003cem\u003eM. tuberculata\u003c/em\u003e. This finding is similar to the results of Paller et al. (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), wherein \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e was the only cercarial morphotype observed to infect more than one snail species. This implies that \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e has low specificity for infection in snail intermediate hosts (Chontananarth and Wongsawad, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEchinostome cercariae develop in rediae and encyst in invertebrates, fish, and amphibians. It is produced by species of the family Echinostomatidae consisting of intestinal parasites of birds, reptiles, and mammals. Documented infections are primarily from members of the genera \u003cem\u003eEchinostoma\u003c/em\u003e, which causes Echinostomiasis and infects the gastrointestinal tract of humans (Centers for Disease Control and Prevention, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). While patients are typically asymptomatic, heavy infections can lead to symptoms like abdominal pain, anorexia, nausea, vomiting, diarrhea, and weight loss due to catarrhal inflammation and mild ulceration. This infection is associated with sociocultural practices such as consuming raw or undercooked mollusks and fish (Sah et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). They utilize species of the genera \u003cem\u003eBiomphalaria\u003c/em\u003e, \u003cem\u003eBulinus\u003c/em\u003e, \u003cem\u003eCeratophallus\u003c/em\u003e, \u003cem\u003eGyraulus\u003c/em\u003e, \u003cem\u003eLentorbis\u003c/em\u003e, \u003cem\u003eLymnaea\u003c/em\u003e, \u003cem\u003ePila\u003c/em\u003e, and \u003cem\u003eSegmentorbis\u003c/em\u003e as intermediate hosts. This study observed two types of \u003cem\u003eEchinostome cercariae\u003c/em\u003e in the freshwater snail samples (Fig.\u0026nbsp;2). Interestingly, these two types were found to infect one host species, the \u003cem\u003eP. acuta\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eLongifurcate-pharyngeate distome cercariae (Strigea cercariae) develops in sporocysts and encysts in snails, tadpoles, reptiles, and fish. Species of the genera \u003cem\u003eBiomphalaria\u003c/em\u003e, \u003cem\u003eBulinus\u003c/em\u003e, \u003cem\u003eCeratophallus\u003c/em\u003e, \u003cem\u003eGyraulus\u003c/em\u003e, \u003cem\u003eLymnaea\u003c/em\u003e, and \u003cem\u003eMelanoides\u003c/em\u003e can serve as intermediate hosts of these parasites. They are produced by species of the Strigeidae and Diplostomatidae families, which include various intestinal parasites of birds and mammals. Recorded infections have been documented chiefly from fishes that serve as secondary intermediate hosts and birds (Ondračkov\u0026aacute; et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). This cercaria was observed from \u003cem\u003eR. quadrasi\u003c/em\u003e samples, a result consistent with Martin I and Cabrera (2018), who reported \u003cem\u003eLymnea (Radix) quadrasi\u003c/em\u003e from ricefields in Batangas, Philippines, to be infected with the \u003cem\u003eStrigea cercariae\u003c/em\u003e parasite.\u003c/p\u003e \u003cp\u003eNematode also was recovered in snails in this study. Generally, nematodes adopt either a free-living or a parasitic lifestyle. Parasitic nematodes include heartworms that infect domestic dogs, hookworms, and pinworms that commonly infect small children. The nematode observed in this study was found in \u003cem\u003eM. maculata\u003c/em\u003e, which was recorded to be one of the hosts of the nematode \u003cem\u003eAngiostrongylus cantonensis\u003c/em\u003e that causes eosinophilic meningitis (Tujan et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In addition, it was found in Site 2 or near the residential areas. This could pose a threat to the people, especially the children living near the lake who are exposed to the waters where such parasites could be present. However, this record is insufficient, given that only one individual sample was recorded to have nematode infection.\u003c/p\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePrevalence Rates of Parasite Infection\u003c/h2\u003e \u003cp\u003eThe total prevalence of parasite infection across all sampling sites is 3.78% (95% CI 2.372\u0026ndash;5.966), a value higher than documented by Paller et al. (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) on the cercarial fauna of freshwater snails (n\u0026thinsp;=\u0026thinsp;2720) of agricultural areas in Laguna, Philippines with only 1.56% total prevalence rate. However, the present study has a lower prevalence rate than the 30.53% total prevalence of parasite infection recorded by Logronio et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) in freshwater snails (n\u0026thinsp;=\u0026thinsp;2460) from the Municipalities of Lala, Kapatagan, and Salvador, Lanao del Norte. It should be noted, however, that they included free-living protozoa (Paramecium) to calculate this prevalence, which may have affected the calculated value. Still, other studies also show a higher total infection prevalence. Chontananarth and Wongsawad (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) reported a 17.27% total prevalence of trematodes in freshwater snails (n\u0026thinsp;=\u0026thinsp;2779) from Chiang Mai province, Thailand while Selbach et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) recorded an overall prevalence of 19.6% of primarily trematode infection among freshwater snails (families Lymnaeidae and Planorbidae; n\u0026thinsp;=\u0026thinsp;5347) in five lakes in Ruhr River system in Germany. A stark difference between this study and those previously reported is the gap between the total number of samples. Nevertheless, recording five cercarial morphotypes and a nematode from the relatively small sample size implies that the Balo-i Lake could also harbor abundant snail and parasite composition.\u003c/p\u003e \u003cp\u003eAmong the parasites observed and identified, the \u003cem\u003eGymnocephalous cercaria\u003c/em\u003e had the highest prevalence with 1.33% (95% CI 0.61\u0026ndash;2.88), followed by \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e with 1.11% (95% CI 0.48\u0026ndash;2.57) (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Although the relative dominance of \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e infection among freshwater snails has been documented by previous studies (Chontananarth and Wongsawad, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Anucherngchai et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), studies that documented \u003cem\u003eGymnocephalous cercaria\u003c/em\u003e from freshwater snails recorded low prevalence (Chontananarth and Wongsawad, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePrevalence of parasite infection per parasite across the three sampling sites, Balo-i Lake, Balo-i, Lanao del Norte, Philippines.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParasite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePower Plant Area\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eResidential Area\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eAgricultural Area\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal Prevalence (%) (CI**)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo. of infected samples and Prevalence (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo. of infected samples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePrevalence (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo. of infected samples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePrevalence (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eTrematode\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCer\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\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.88\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.22 (0.04\u0026ndash;1.25)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePar\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\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.11 (0.48\u0026ndash;2.57)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGym\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\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.26\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.33 (0.61\u0026ndash;2.88)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEch\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.44 (0.12\u0026ndash;1.61)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStr\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.44 (0.12\u0026ndash;1.61)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNon-trematode\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNematode\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\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.88\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.22 (0.04\u0026ndash;1.25)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003cem\u003e**95% Confidence Interval\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003cem\u003eCer: Cercarium cercaraie, Par: Parapleurolophocercous cercaria, Gym: Gymnocephalous cercariae, Ech: Echinostome cercariae, and Str: Strigea cercariae.\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eStill, the findings in this study are similar to those reported by Phiri et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), wherein \u003cem\u003eGymnocephalous cercaria\u003c/em\u003e was also the most common cercarial type observed from snail samples of the Kafue wetlands of Zambia. Interestingly, the Kafue River within this wetland is utilized for the generation of electricity, similar to how water flowing into Balo-i Lake is used by Agus IV to generate electricity.\u003c/p\u003e \u003cp\u003eThe prevalence rates among sampling sites showed that Site 2 (Residential Area) had the highest prevalence rate with 7.89% (95% CI 4.21\u0026ndash;14.33), followed by Site 3 (Agricultural Area) with 3.74% (95% CI 5.39\u0026ndash;12.9). In contrast, Site 1 (Power Plant) had no infected samples. These results can be attributed to the difference in the characteristics of each sampling site. In the Power Plant area, the presence of the riprap wall with connecting roads represents habitat modification, which is a significant threat to biodiversity (World Wide Fund for Nature, \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Marcogliese (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) reported that multi-host parasites, particularly those with complex life cycles and free-living infectious stages such as the trematodes and nematodes, should be affected by changes in biodiversity more than directly transmitted specialists. Thus, the parasites that use snails as intermediate hosts cannot accomplish their life cycles since not many final hosts exist within the area. According to Jayawardena et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), the diversity of digenean trematodes is dependent on conditions that are conducive to transmission, such as the presence of final and intermediate hosts. Thus, although some birds were observed flying around this site, the type of parasites that could thrive in the area is limited.\u003c/p\u003e \u003cp\u003eOn the other hand, the site near residential areas (Site 2) had a ground area with trees and frequent human activities like washing clothes. In addition, near this area is a small isolated or caged area most likely placed for fish collection. Ducks were sighted swimming around, and amphibians were also observed while collecting snails on this site. Pollution was evident in this site as many plastic and waste materials were observed floating and scattered around.\u003c/p\u003e \u003cp\u003eThe last site, Site 3, was near agricultural areas with an open grassland area directly adjacent to the lake, and grazing animals like cows could be seen. Large birds were seen flying over while ducks were swimming, and many insects, including dragonflies, were flying across small flowering plants. Human activities were also present, as people doing their laundry were seen in the area. Anthropogenic activities such as open field defecation, urination, livestock grazing, farming, and swimming were highly correlated with trematode infection (Mereta et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePrevalence among species was highest for \u003cem\u003eR. quadrasi\u003c/em\u003e with 40% (95% CI 11.76\u0026ndash;76.93), a value which may have been influenced by its very small sample size (n\u0026thinsp;=\u0026thinsp;5) as well as the susceptibility of \u003cem\u003eR. quadrasi\u003c/em\u003e to parasite infection, along with other species from the same genus (Sold\u0026aacute;nov\u0026aacute; et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Huňov\u0026aacute; et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Martin I and Cabrera, 2018) and family (Correa et al. 2010). Meanwhile, \u003cem\u003eM. tuberculata\u003c/em\u003e has the lowest prevalence rate with 2.27% (95% CI 0.40\u0026ndash;11.81) despite being a species with many published studies documenting it harboring different parasites (Ballesteros and Dela Paz, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Tujan et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Najet, 2014; Yousif et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePhysicochemical parameters are among the factors that can affect the prevalence of parasite infection among freshwater snails. In this study, physicochemical parameters (pH and temperature) of the three sampling sites in Balo-i Lake were recorded, with the Power plant area recorded at 6.84 pH in August 2023 while 7.65 pH in the month of March 2024 and 26.5 temperature (\u0026deg;C) in August while 28.4\u0026deg;C in August. Likewise, the Residential area had 7.43 pH in August, 7.33 pH in March, and 26.9\u0026deg;C temperature in August, while 27.6\u0026deg;C as well as Agricultural area recorded 7.75 pH in August while 7.98 pH in March and 27.7\u0026deg;C temperature in August while 29.1\u0026deg;C in March. As described in the previous section, increased temperature generally increases the prevalence. In terms of pH, Logronio (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) described that pH and infected snails showed a negative correlation and a positive correlation to non-infected, supported by further regression analysis. The prevalence of parasite infection was 0% in August or the wet season, while 6.42% was in March or the dry season. This difference can be attributed to the seasonal changes in rainfall, temperature, and food availability that can affect the intensity or prevalence of parasitism through changes in host susceptibility (Shearer and Ezenwa, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), or changes in host exposure influenced by seasonal variation in host behavior (Petrić et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) or parasite development and survival (Zamora-Vilchis et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite these mechanisms, all findings suggest a strong and positive association between parasite prevalence and temperature. Parasite prevalence increased during the dry season, as observed from parasite-host interactions of helminths and many host species, including fishes, mammals, and birds (Shearer and Ezenwa, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Zamora-Vilchis et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Thus, the data for the parasites observed during the August sampling must be lower than during the March sampling. This is consistent with the findings of Purwaningsih et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), wherein the highest prevalence of \u003cem\u003eFasciola gigantica\u003c/em\u003e, a trematode, infection in \u003cem\u003eLymnaea\u003c/em\u003e sp. snails was highest in November when the rainfall was low, and was lowest in April when the recorded rainfall was at its peak.\u003c/p\u003e \u003cp\u003eAlso, the study by Rowel et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) showed that the cercarial shedding of snails (\u003cem\u003eBiomphalaria\u003c/em\u003e) has a positive relationship with temperature and a negative relationship with pH. In this study, however, given the pH and temperature values in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the correlation between parasite infection and pH and temperature is technically positive but is too weak. P-values were not significant at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003cp\u003eThese inconsistent results imply that the seasonal difference in the prevalence of infection may have been influenced more by rainfall patterns and indirect changes in the host and environmental conditions instead of the temperature and pH levels. Human activities and disturbances could also be a factor in altering water flow patterns, changing the habitat structure, and disrupting the life cycle of some parasite species. Other studies that explored the shedding of cercariae by freshwater snail species showed a non-linear relationship between pH and temperature and the cercarial emergence. It was instead a range of optimum pH and temperature levels (20\u0026ndash;25\u0026deg;C for monostome type and 25\u0026ndash;30\u0026deg;C for \u003cem\u003ePleurolophocercous cercariae\u003c/em\u003e) that induced cercarial shedding (Achiorno and Martorelli, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe presence of documented parasites, including trematodes and nematodes, suggests the presence and abundance of vertebrate definitive and intermediate hosts needed to complete their life cycle. This indicates that the community, especially sites 2 and 3, the residential and agricultural areas, still have birds, fishes, reptiles, and mammals that are thriving and helping support the parasite population to persist. However, the presence of these parasites also has implications for public health and veterinary medicine concerning the risk they pose to the animals and humans living near and around Balo-i Lake. Most of the parasites observed are cercarial morphotypes produced by pathogenic groups, including intestinal parasites of fish, birds, and mammals.\u003c/p\u003e \u003cp\u003eThe prevalence of parasitic zoonoses, facilitated by freshwater snails acting as intermediate hosts, has increased human mortality and morbidity as these snails are utilized for food and medicinal purposes (Logronio, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Although parasites, in general, are essential in keeping the balance in an ecosystem, human disturbances and alterations can tweak this balance, causing harmful effects and diseases to humans. With freshwater snails as a point of transmission, it is essential that control measures, including proper sanitation and possibly managing parasite hosts, be in place to prevent, manage, and control diseases (Pathak, et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). These measures aim to mitigate the transmission of diseases and reduce their impact on human and animal populations. Johnson et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) emphasized the importance of collaboration of ecological and parasitological research in the mediation of transmission of human pathogens as their findings showed that increased community diversity reduced \u003cem\u003eSchistosoma\u003c/em\u003e infection among snail hosts (\u003cem\u003eBiomphalaria glabrata\u003c/em\u003e) by 20\u0026ndash;50%. Thus, maintaining a diverse and healthy ecosystem can be a way to control and mitigate disease transmission by parasites.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eConclusion and Recommendation\u003c/h2\u003e \u003cp\u003eThe presence of parasites in Balo-i Lake has implications for public health and veterinary medicine, particularly for communities close to the lake. Control measures, including proper sanitation and management of parasite hosts, are crucial for preventing and managing disease transmission. Maintaining a diverse and healthy ecosystem may help mitigate disease transmission by reducing host susceptibility to infection. Future studies in the lake include more sampling days and time and other areas around the lake for more comprehensive results; molecular analysis can be utilized to identify parasites to provide more insight into their composition, abundance, and implications for the people and animals surrounding the lake. Regular surveillance of parasite infections in freshwater snails is in place to detect changes in prevalence rates and understand parasite dynamics to aid public health. Community engagement and education programs are implemented to raise awareness of the health risks associated with parasite infections and to promote practices that reduce exposure. Efforts to preserve and restore the ecological integrity of the lake and its surrounding habitats are made to maintain a healthy ecosystem and reduce the risk of disease transmission. Through these recommendations and adopting a holistic approach to parasite control, we can work towards safeguarding the health and well-being of communities living near Balo-i Lake and preserving the ecological balance of this freshwater ecosystem.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompliance with ethical standards\u003c/h2\u003e \u003ch2\u003eConflict of interest\u003c/h2\u003e \u003cp\u003eNone declared\u003c/p\u003e \u003ch2\u003eAuthor contribution\u003c/h2\u003e \u003cp\u003eConceived and designed sampling: JDB, LJGM, and LAE performed the collection of samples and laboratory analysis as well as the writing of the paper.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003e The author would like to express the most profound appreciation and gratitude to the local government units (LGU) and locals of Nangka, Balo-i, Lanao del Norte, for assistance during the collection of samples and to the Department of Biological Sciences, College of Science and Mathematics, Center for Biodiversity Studies and Conservation of Premier Research Institute of Science and Mathematics for allowing the researcher to conduct the processing of samples and laboratory analysis. To the Agus IV Hydroelectric Power Plant Management and the Department of Science and Technology-Science Education Institute for funding this research.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAchiorno CL, Martorelli SR (2016) Effect of temperature changes on the cercarial-shedding rate of two trematodes. Iheringia Serie Zoologia 106:e2016020. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1590/1678-4766e2016020\u003c/span\u003e\u003cspan address=\"10.1590/1678-4766e2016020\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnucherngchai S, Tejangkura T, Chontananarth T (2016) Epidemiological situation and molecular identification of cercarial stage in freshwater snails in Chao-Phraya Basin, Central Thailand. 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PLoS ONE 7(6):e39208. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1371/journal.pone.0039208\u003c/span\u003e\u003cspan address=\"10.1371/journal.pone.0039208\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-parasitic-diseases","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jopd","sideBox":"Learn more about [Journal of Parasitic Diseases](https://www.springer.com/journal/12639)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/jopd/default.aspx","title":"Journal of Parasitic Diseases","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"cercariae, infection, lake, nematode, trematode","lastPublishedDoi":"10.21203/rs.3.rs-4891076/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4891076/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFreshwater snails play crucial roles in aquatic habitats with essential ecosystem functions and services. However, they also serve as intermediate hosts for various parasites that pose risks to human and animal health. This study aimed to identify freshwater snail species with parasite infection and assess parasite prevalence in Balo-i Lake, Lanao del Norte, Philippines. Snail samples were collected from three sites (Power Plant area, Residential area, and Agricultural area) around the lake utilizing the belt transect method, and parasites were identified based on morphological characteristics. Physicochemical parameters were measured to explore their correlation with parasite prevalence. Results revealed a total prevalence rate of 3.78% (95% CI 2.372\u0026ndash;5.966) among five freshwater snail species \u0026ndash; \u003cem\u003eS. angularis\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;26), \u003cem\u003eP. acuta\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;22), \u003cem\u003eM. maculata\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;81), \u003cem\u003eM. tuberculata\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;44), and \u003cem\u003eR. quadrasi\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;5), with notable variations among sampling sites and seasonal variation between wet and dry seasons. \u003cem\u003eM. maculata\u003c/em\u003e harbored the most parasites, with three cercarial morphotypes and a nematode. Trematodes were the most abundant parasites, with five morphotypes identified, namely \u003cem\u003eCercarium cercariae\u003c/em\u003e, \u003cem\u003eGymnocephalous cercariae\u003c/em\u003e, \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e, \u003cem\u003eEchinostome cercariae\u003c/em\u003e, and \u003cem\u003eStrigea cercariae\u003c/em\u003e, most of which are produced by intestinal parasites of fish, birds, and mammals. \u003cem\u003eGymnocephalous cercariae\u003c/em\u003e infected most snail individuals (n\u0026thinsp;=\u0026thinsp;6), but \u003cem\u003eParapleurolophocercous cercaria\u003c/em\u003e was the most common, infecting three snail species across two sampling sites. The residential area has the highest prevalence rate of infection, likely influenced by frequent human activities like bathing, washing clothes, pollution, and the presence of potential hosts such as ducks, amphibians, and mammals in adjacent areas. Weak correlations between parasite prevalence and pH and temperature suggest additional influencing factors. The presence of parasites highlights public health concerns, emphasizing the need for control measures and ecosystem conservation to mitigate disease transmission in the area.\u003c/p\u003e","manuscriptTitle":"Prevalence of parasites in freshwater snails with notes on helminth-associated diseases in Balo-i Lake, Lanao del Norte, Philippines","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-11 08:02:30","doi":"10.21203/rs.3.rs-4891076/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-07-14T11:49:25+00:00","index":0,"fulltext":""},{"type":"editorInvited","content":"Journal of Parasitic Diseases","date":"2025-07-13T09:59:44+00:00","index":"","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-08-14T16:43:09+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-10T11:50:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Parasitic Diseases","date":"2024-08-10T05:16:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-parasitic-diseases","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jopd","sideBox":"Learn more about [Journal of Parasitic Diseases](https://www.springer.com/journal/12639)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/jopd/default.aspx","title":"Journal of Parasitic Diseases","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"64275268-102a-42fb-836f-bbd1b79a9e5b","owner":[],"postedDate":"September 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-02T16:02:01+00:00","versionOfRecord":{"articleIdentity":"rs-4891076","link":"https://doi.org/10.1007/s12639-026-01920-9","journal":{"identity":"journal-of-parasitic-diseases","isVorOnly":false,"title":"Journal of Parasitic Diseases"},"publishedOn":"2026-02-26 15:58:45","publishedOnDateReadable":"February 26th, 2026"},"versionCreatedAt":"2024-09-11 08:02:30","video":"","vorDoi":"10.1007/s12639-026-01920-9","vorDoiUrl":"https://doi.org/10.1007/s12639-026-01920-9","workflowStages":[]},"version":"v1","identity":"rs-4891076","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4891076","identity":"rs-4891076","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}