Epidemiological factors associated with the spatial distribution of two Rickettsia hosts in a locality of Yucatán, Mexico

Epidemiological factors associated with the spatial distribution of two Rickettsia hosts in a locality of Yucatán, Mexico | 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 Epidemiological factors associated with the spatial distribution of two Rickettsia hosts in a locality of Yucatán, Mexico Abigail Arroyo-Ramírez, César Lugo-Caballero, Enrique Reyes-Novelo, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4451515/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Rickettsioses caused by the spotted fever group (SFG) and typhus group (TG) are endemic in southeastern Mexico. Dogs and rodents can host several species of these bacteria, but little is known about the epidemiological factors that influence the infection risk in these mammals. This study aims to identify the frequency of Rickettsia SFG and TG infection in the studied animals, to determine the spatial distribution of the hosts, and to identify the factors associated with the infection risk. Genomic DNA was obtained from 66 dog blood samples and 36 rodent spleens collected in 48 dwellings from the rural locality of Ucú, Yucatan, Mexico. Rickettsia SFG or TG infection was determined using a multiplex semi-nested PCR (snPCR). The predictor variables for the infection risk in dogs and rodents were selected using generalized linear models (GLM) ( p < 0.05). snPCR revealed Rickettsia DNA in 28.1% (18/64, 95% CI 17.6%-40.8%) of dogs and 27.8% (10/36, 95% CI 14.2%-45.2%) rodents. Only Rickettsia SFG was detected in dogs, while rodents hosted both Rickettsia TG and SFG. According to the corresponding GLM, dogs living in the interior area of Ucú have a lower risk of infection by Rickettsia SFG (RR = 0.14) than those living in the other areas. The presence of opossums ( Didelphis sp.) in the dwelling increases the risk of Rickettsia TG infection in rodents (RR = 14), and the presence of SFG-infected dogs in the dwelling increases the risk of Rickettsia SFG infection in rodents (RR = 21). Epidemiology vector-borne diseases rickettsiosis companion animals synanthropic animals animal health Figures Figure 1 Introduction Rickettsioses is a group of infectious diseases caused by the genera Orientia and Rickettsia bacteria. They are transmitted through the bite or feces of hematophagous ectoparasites such as ticks, lice, fleas, and mites (Gillespie and Salje 2023 ). According to its genomic characteristics, Rickettsia includes five groups: 1) Bellii , 2) transitional, 3) typhus (TG), 4) Tamurae / Ixodes , and 5) spotted fever (SFG) (Verhoeve et al. 2022 ). Rickettsiosis caused by Rickettsia shows a wide range of prevalence and incidence rates across different regions of Mexico. According to Sánchez-Montes et al. ( 2021a ) and Torres-Castro et al. ( 2024 ), the prevalence of this bacteria genus is higher in the northern and southeastern states of the country. In inhabitants from the Yucatan peninsula, southeastern Mexico, some species belonging to the SFG, such as R . rickettsii (Torres-Castro et al 2022a )d parkeri (Peniche-Lara and Lara-Perera 2022 ; Torres-Castro et al. 2022b ), and belonging to TG, such as R . typhi , have been found (Torres-Castro et al. 2022a ). The zoonotic foci of Rickettsia SFG and TG, including mammal hosts or ectoparasites vectors, have not been figured out (Torres-Castro et al. 2024 ). However, certain biotic and abiotic factors increase the risk of contact or infection with Rickettsia groups in localities of Yucatan state. These factors include a younger age for people living in rural localities, having peridomestic family gardens (orchards), and the presence of free-living vector arthropods in the peridomicile (Torres-Castro et al. 2020 b). Similarly, households with at least one case of human rickettsiosis recorded the presence of animals positive for Rickettsia SFG or TG (Dzul-Rosado et al. 2021 ). These last findings suggest the potential role of dogs (companion animals), rodents, and other synanthropic animals in the transmission cycles of Rickettsia (Torres-Castro et al. 2024 ). Dogs and rodents are hosts of several pathogenic Rickettsia species, taking part in their epidemiological cycles' transmission, maintenance, and dispersion (Moreira-Soto et al. 2016 ; Sánchez-Montes et al. 2021a ; Arroyo-Ramírez et al. 2022 ). In Yucatan, these animals are hosts of pathogenic species, such as R . felis (Panti-May et al. 2015 ), R. typhi (Peniche-Lara et al. 2015a ; Martínez-Ortiz et al. 2016 ; Torres-Castro et al. 2018 )d parkeri (Ojeda-Chi et al. 2019 ; Arroyo-Ramírez et al. 2023 ), and also for several species of Rickettsia vector ectoparasites (Peniche-Lara et al. 2015a , b ; Martínez-Ortiz et al. 2019 ; Ojeda-Chi et al. 2019 ; Torres-Castro et al. 2022c ). The spatial distribution of these host animals is a relevant feature for the understanding of the Rickettsia infection risk, particularly in inhabited areas (Quintero et al. 2018; Torres-Castro et al. 2022c ; Arroyo-Ramírez et al. 2023 ). Recent studies that explored the spatial distribution of arthropod vectors and rickettsial hosts reveal that infection tends to occur in spatial clusters where mammal hosts and ectoparasitic arthropods converge (Dzul-Rosado et al. 2021 ). However, the generalized distribution of companion animals like dogs and synanthropic fauna and their ectoparasites in human settlements makes it challenging to understand Rickettsia infection risk. This study aims to identify the frequency of Rickettsia SFG and TG infection in the studied animals, to determine the spatial distribution of the hosts, and to identify the factors associated with the infection risk at locality scale. Materials and methods Study site The study was conducted in the locality of Ucú (22°01′55″ N, 89°44′47″ W), located in the state of Yucatan, Mexico, in the municipality of the same name (Fig. 1 ). The municipality has a territorial total area of 130.8 km 2 and an average altitude of 8 m above sea level. Ucú is part of the metropolitan area of Merida City, which is the capital of Yucatan (INAFED 2021). The study site has a population of approximately 4,049 residents who live in 1,139 dwellings within the town (INEGI 2020). The region has a warm, subhumid climate with summer rainfall. The average annual temperature is 26° C, and rainfall is 800 mm (INAFED 2021). The original vegetation includes low deciduous forests surrounded by patches of secondary and introduced vegetation, such as pastures for cutting and forage and temporary agriculture, as well as infrastructure such as dwellings, warehouses, parks, roads, and streets (Quiroz-Carranza and Orellana 2007). Study design The study design was descriptive and cross-sectional. Due to the sanitary restrictions caused by the CoViD-19 pandemic, the sample size was obtained based on the number of occupied dwellings (1,139) with the formula to calculate a sample size to estimate a frequency (Thrusfield 2007 ), using a confidence level of 95%, precision of 80%, and expected proportion of 6% of animal captures accordingly with previous studies in the region (Panti-May et al. 2016 ; Torres-Castro et al. 2022c ). To cover the total extension of the study site, two imaginary lines that crossed its center were drawn to divide it into three concentric areas (interior, central, and exterior). For a homogeneous distribution of the dwellings, sixteen per area for 48 total dwellings throughout the study site were considered (Fig. 1 ). Dwellings were selected by convenience, and those whose owners signed informed consent to participate in the study were included in the sample. Biological samples From August to October 2021, a single visit to each dwelling was carried out. Puppies < 2 months of age and dogs that had received antibiotic treatment at least two months before the visit, according to the information provided by the owner, were excluded. Before blood sampling, the venipuncture skin area was sanitized with iodine and hydrogen peroxide to prevent cross-contamination with ectoparasite feces. Each dog's peripheral blood sample (up to 5 ml) was collected through femoral or cephalic vein puncture using 5 ml sterile syringes (BD Plastipak, Mexico) and placed in tubes with heparin (BD Vacutainer® PST, USA). During fieldwork, the samples were kept in portable iceboxes with refrigerants. All samples were then transferred to the laboratory to be centrifuged at 1,500 g for 10 min at room temperature to separate the plasma stored in a 1.8 ml microcentrifuge tube (Eppendorf®, USA) at -80° C until diagnostic procedures. Ten Sherman traps (8 x 23 x 9 cm; HB Sherman Traps Inc.®; USA) per dwelling were used to capture rodents. Traps were baited with oat flakes and artificial vanilla flavoring and placed only in the peridomicile area for two consecutive nights, resulting in a total capture effort of 960 nights/trap. The captured rodents were transported to the laboratory facilities for further processing. Rodent species using field guides were identified (Reid 2009 ). All rodents were anesthetized with isoflurane (Piramal Enterprises Limited®; United Kingdom) and euthanized with an overdose (90–210 mg/kg) of pentobarbital sodium (Aranda®; Mexico). After euthanasia, the abdominal cavity was opened, and the spleen was collected and stored in 1.8 ml microcentrifuge tubes at -80° C. Animal data collection Dog data was collected by applying a questionnaire to each animal's owner on the day of blood sampling and visually inspecting the animals. The data collected included information on the sex (male or female) and age (puppy: < 1 year, adult: 1 to 6 years, or geriatric: ≥ 6 years [Torres-Castro et al. 2022c ]). Additionally, the study examined whether the animals were recently infested with ticks or fleas (positive [yes] or negative [no], regardless of the number of ectoparasites) and the level of infestation (regardless of the type of ectoparasite [tick or flea]). Infestation levels assessed by visual inspection were classified as negative (no presence of ectoparasites), mild (≤ 10 ectoparasites), moderate (11 to 30 ectoparasites), or severe (> 30 ectoparasites) (Torres-Castro et al. 2022c ). Lastly, the study also considered whether the animals had access to roam outside the dwelling (yes or no, regardless of time). Rodent data was collected on sex (male or female), age (adult or juvenile), weight (≤ 10 g or > 10 g), and reproductive conditions (active or inactive) (Panti-May et al. 2016 ). Dwelling data collection The questionnaire also gathered information on dwelling characteristics, location (interior, central, and exterior), the presence/absence of 1) companion animals other than dogs (e.g., cats, rabbits, etc.), 2) production animals (e.g., cattle, goats, sheep, horses, and poultry), and 3) synanthropic fauna (rodents or opossums). To monitor the presence/absence of opossums ( Didelphis sp.), a Tomahawk trap (23 x 23 x 66 cm, Tomahawk Live Trap Inc.®, USA) was placed per dwelling, along potential routes passing (e.g., fences, fruit trees, orchards). Traps were baited with seasonal fruit and kept open during the same consecutive nights of rodent trapping, resulting in a total capture effort of 96 nights/trap. All captured opossums were released in the nearest forested area to the study locality. Genomic DNA extraction and identification of Rickettsia groups Genomic DNA was extracted from blood samples and spleens using the Wizard Genomic DNA Purification Kit® (Promega®, USA). The extracted DNA was then assessed for its quality (A260/280) and concentration (ng/µl) using a Nanodrop™ (Thermofisher Scientific™, USA). Subsequently, the DNA samples were stored at -20° C until used to detect Rickettsia DNA. To identify Rickettsia groups (SFG and TG), a semi-nested multiplex PCR (snPCR) targeting a fragment of sca5 , which encodes a fragment of the outer membrane protein B (omp B) in all Rickettsia members, was performed. In the first round, the oligonucleotides rOmpB OF (5’-GTAACCGGAAGTAATCGTTTCGTAA-3’), rOmpB OR (5’-GCTTTATAACCAGCTAAACCACC-3’) (Choi et al. 2005 ), and rOmpB-804 Fw TG (5’-GAATCAACTGATACAGCAGC-3’) were used. In the second, the oligonucleotides rOmpB SFG IF (5'-GTTTAATACGTGCTGCTAACCAA-3'), rOmpB SFG/TG IR (5'-GGTTTGGCCCATATACCATAAG-3') (Choi et al. 2005 ), and rOmpB TG IF (5'-AAGATCCTTCTGATGTTGCAACA-3') were used. For the first round, initial denaturation at 95°C for 5 min was followed by 35 cycles of denaturation at 95°C for 15 sec, alignment at 54°C for 15 sec, extension at 72°C for 30 sec, and a final extension of 72°C for 3 min. The same conditions were used for the second round, but the alignment temperature was changed to 56°C. The final extension was conducted at 72° C for 3 min (Arroyo-Ramírez et al. 2023 ). Due to the low genetic similarity between these two Rickettsia groups, this snPCR produces amplified fragments of two sizes: 420 base pairs (bp) for the SFG and 237 bp for the TG (Choi et al. 2005 ). Previously characterized positive controls were used to confirm that the reactions were done correctly (Torres-Castro et al. 2020 b, c). The negative control was the PCR mixture without any template DNA. Electrophoresis was performed in 10% polyacrylamide gels (Sigma-Aldrich Products®, Germany) deposited in vertical cameras (Bio-Rad Laboratories®, USA) and stained with 1.1 molar silver nitrate. For the final visualization and recording of the results, a UV light transilluminator was used (Hoefer®, USA). The sample that showed amplification was considered positive for Rickettsia infection. Statistical analysis Descriptive statistics were used to analyze snPCR results and determine Rickettsia infection frequencies and percentages in the studied animals. The Clopper-Pearson procedure estimated 95% confidence intervals (CI) using the Quantitative Parasitology package for R (Rózsa et al. 2000 ; Reiczigel et al. 2019 ). A Fisher's exact test was used to determine the statistical association between the frequency of infected animals and the surveyed variables related to biological or dwelling characteristics. Those associations with a p < 0.3 were considered significant for inclusion as independent variables in the modeling analyses with generalized linear models. A generalized linear model (GLM) with binomial error distribution was used to select predictor variables for the risk of Rickettsia infection in dogs. The dependent variable for the dog's data was the animal's status according to snPCR results (positive or negative for infection with SFG). The rodent’s data was analyzed by a multinomial GLM using the dependent variable of the infection group with three levels: 1) "Not infected" or "negative," 2) "SFG infected," and 3) "TG infected." The "negative" level was used as a reference. Akaike’s information criterion was used to select the best-fit model. The statistical significance was set at a p < 0.05. The relative risk (RR) and a 95% confidence interval (CI) were estimated. R software version 3.9.0 in the RStudio programming environment helped with the statistical analyses (R Core Team 2024 ). Results One hundred animals were studied; 64% were dogs, and 36% were rodents. Of the studied dogs, 57.8% (37/64) were males and 42.2% (27/64) were females. About age, 21.8% (14/64) were puppies, 67.2% (43/64) were adults, and 10.9% (7/64) were geriatric. The results showed that 29.7% (19/64) had fleas, and 75% (48/64) had ticks. The infestation levels, regardless of the type of ectoparasite (fleas or ticks), were distributed as follows: 7.8% (5/64) had no infestations, 67.2% (43/64) had mild infestations, 20.3% (13/64) had moderate infestations, and 4.7% (3/64) had severe infestations. Moreover, 73.4% (47/64) of the studied dogs had free access to roam outside the dwelling and its peridomicile (Table 1 ). Table 1 Frequency of Rickettsia SFG infection and the characteristics of the dogs and dwellings of Ucú, Yucatan, Mexico, and its respective P -value from the Fisher’s exact test for the predictor variable selection. Variables Dogs (%) n = 64 SFG (%) n = 18 P -value Dog characteristics Sex Male Female 37 (57.8) 27 (42.2) 9 (50) 9 (50) 0.6 Age Puppy Adult Geriatric 14 (21.8) 43 (67.2) 7 (10.9) 6 (33.3) 9 (50) 3 (16.7) 0.18* Flea infestation Presence Absence 19 (29.7) 45 (70.3) 3 (16.7) 15 (83.3) 0.22* Tick infestation Presence Absence 48 (75) 16 (25) 15 (83.3) 3 (16.7) 0.52 Infestation level Null Mild Moderate Severe 5 (7.8) 43 (67.2) 13 (20.3) 3 (4.7) 1 (5.6) 12 (66.7) 4 (22.2) 1 (5.6) 0.96 Access to roam Yes No 47 (73.4) 17 (26.6) 15 (83.3) 3 (16.7) 0.41 Dwelling characteristics Location Interior Central Exterior 19 (29.7) 19 (29.7) 26 (40.6) 2 (11.1) 6 (33.3) 10 (55.6) 0.11* Production animals Presence Absence 40 (62.5) 24 (37.5) 11 (61.1) 7 (38.9) 1 Companion animals Presence 56 (87.5) 17 (94.4) 0.52 Absence 8 (12.5) 1 (5.6) Synanthropic animals Presence 36 (56.2) 12 (66.7) 0.17* Absence 28 (43.8) 6 (33.3) Rodents Presence Absence 30 (46.9) 34 (53.1) 10 (55.6) 8 (44.4) 0.55 Opossums Presence Absence 16 (25) 48 (75) 3 (16.7) 15 (83.3) 0.52 * p < 0.3 Regarding the characteristics of the dwellings, 29.7% (19/64) of sampled dogs were from dwellings in the interior area, the same amount from the central area, and 40.6% (26/64) of dogs were from dwellings of the exterior area; 62.5% (40/64) of the sampled dogs coincided with at least one production animal; 87.5% (56/64) coincided with companion animals different from dogs; 46.9% (30/64) were sampled in dwellings with rodents, and 25% (16/64) of the studied dogs were from dwellings with opossums (Table 1 ). In the captured rodents, 88.9% (32/36) were Mus musculus , 8.3% (3/36) were Peromyscus yucatanicu s, and 2.8% (1/36) were Ototylomys phyllotis . Among them, 66.7% (24/36) were males and 33.3% (12/36) were females. The adult rodents were 86.1% (31/36), and juveniles were 13.9% (5/36). According to the dwellings’ characteristics, 27.8% (10/36) of the rodents were captured in the interior area, 16.7% (6/36) in the central area, and 55.6% (20/36) in the exterior area; 58.3% of rodents (21/36) were from dwellings with at least one production animal and 80.6% (29/36) were from dwellings with companion animals. Records of opossum presence were for 16.7% (6/36) of captured rodents. snPCR testing revealed Rickettsia DNA in 28.1% (18/64, 95% CI 17.6%-40.8%) of dogs and 27.8% (10/36, 95% CI 14.2%-45.2%) rodents. All Rickettsia -positive dogs were for SFG. The distribution of these dogs was equal between females and males (50%, 9/18); 50% (9/18) were adults, 33.3% (6/18) were puppies, and 16.7% (3/18) were geriatrics (Table 1 ). Of the Rickettsia -positive rodents, 90% (9/10) were M . musculus and 10% (1/10) were P . yucatanicus ; 70% (7/10) were positive for SFG, including the individual P . yucatanicus , while 30% (3/10) were positive for TG, all of which were M . musculus . Among these infected rodents, 80% (8/10) were male and 20% (2/10) were female. Additionally, 80% (8/10) were adults, and 20% (2/10) were juveniles (Table 2 ). Finally, 16.7% (6/36) of the captured rodents coincided with at least one dog with Rickettsia infection. Table 2 Frequency of Rickettsia SFG and TG infection detected by multiplex semi-nested polymerase chain reaction concerning the characteristics of the rodents and dwellings from Ucú, Yucatan, Mexico, and their respective P -value returned by the Fisher’s exact test for the selection of the predictor variables. Variables SFG (%) P-value TG (%) P-value Rodents’ characteristics Sex Male Female 6 (85.7) 1 (14.3) 0.38 2 (66.7) 1 (33.3) 1 Age Juvenil Adult 1 (14.3) 6 (85.7) 1 1 (33.3) 2 (66.7) 0.37 Weight (gr) 10 1 (14.3) 6 (85.7) 0.49 1 (33.3) 2 (66.7) 0.23* Reproductive condition Male Active Inactive Female Active Inactive 6 (85.7) 0 0 1 (14.3) -- 2 (66.7) 0 1 (33.3) 0 -- Dwellings’ characteristics Dwelling location Interior Central Exterior 1 (14,3) 2 (28,6) 4 (57,1) 0.54 0 0 3 (100) -- Production animals Presence Absence 5 (71.4) 2 (28.6) 0.67 2 (66.7) 1 (33.3) 1 Other companion animals Presence Absence 6 (85.7) 1 (14.3) 1 2 (66.7) 1 (33.3) 0.49 Opossums Presence Absence 1 (14.3) 6 (85.7) 1 2 (66.7) 1 (33.3) 0.07* Dogs with Rickettsia spp. Presence Absence 4 (57.1) 3 (42.9) 0.007* 0 3/3 (100) -- * p < 0.3 The exploratory bivariate analyses showed statistical associations between infected dogs with Rickettsia SFG with age, flea infestation, dwelling location, and presence of synanthropic animals (Table 1 ). In contrast, the best predictor variables for the presence of Rickettsia infection in rodents were 1) the presence of opossums for TG Rickettsia and 2) the presence of SFG-infected dogs for SFG Rickettsia (Table 2 ). The final binomial GLM with the smallest AIC value (76.33) for SFG-infected dogs included the predictor variables “dwelling location” and “other companion animals.” The model showed that dogs from the interior area have a lower risk (RR = 0.14; 95% CI 0.02–0.65) of Rickettsia SFG infection than dogs from the other areas (Table 3 ). Table 3 Results of the best Generalized Linear Model with binomial error distribution to identify the risk ratio (RR) and its 95% confidence intervals (CI) of Rickettsia Spotted Fever Group (SFG) infection in the studied dog population from Ucú, Yucatan, Mexico. Variables P-value RR 95% CI Area 0.13–1.88 0.02–0.65 Exterior -- Central 0.32 0.51 Interior 0.02 0.14 Other companion animals Absence Presence -- 0.14 5.57 0.77–115.2 The multinomial model with the lowest AIC value (53.68) showed a higher risk of Rickettsia TG infection (RR = 14; 95% CI 0.95–206) in rodents captured in dwellings with presence of opossum and a higher risk of Rickettsia SFG infection (RR = 21; 95% CI 2.3–196) in rodents captured in dwellings with presence of an SFG-infected dog (Table 4 ). Table 4 Results of the multinomial stratified model to identify the risk ratio (RR) and its 95% confidence intervals (CI) of Rickettsia Spotted Fever Group (SFG) and Typhus Group (TG) infection in the studied rodent populations of Ucú, Yucatan, Mexico. Variables P -value RR 95% CI Presence of opossums Negative TG SFG -- 0.05* 0.36 14 3.5 0.95–206 0.24–51.5 Presence of SFG-infected dogs Negative TG SFG -- 0.93 0.008* 0.002 21 3 e − 62 -1.6 e + 56 2.3–196 * p < 0.05 Discussion In southeastern Mexico, studies that report Rickettsia TG and SFG infection have been conducted in rodents (Peniche-Lara et al. 2015a ; Torres-Castro et al. 2018 ; Arroyo-Ramírez et al. 2023 ) and dogs (Martínez-Ortiz et al. 2016 ; Torres-Castro et al. 2022c ; Arroyo-Ramírez et al. 2023 ). However, knowledge about the biotic or abiotic factors that influence the transmission and infection in these animals is limited (Ojeda-Chi et al. 2019 ). Therefore, the results of this research contribute to the understanding of the epidemiological elements involved in the transmission dynamics of these vector-borne bacteria, which are important for public health because of their capacity to generate outbreaks (Torres-Castro et al. 2018 ; Sánchez-Montes et al. 2021a ; Carrasquilla et al. 2023 ). The snPCR performed in the studied dogs only revealed the infection of Rickettsia SFG, which differs from the reported by Torres-Castro et al. ( 2022c ) in dogs from Maxcanú, Yucatan, infected with Rickettsia TG. However, it is essential to mention that the sampling months are different, influencing the abundance and richness of vector ectoparasites (Rodríguez-Vivas et al. 2023 ). Contact of dogs with Rickettsia SFG has been documented in several countries with endemic areas. For example, antibodies against this Rickettsia group were found in dogs from Costa Rica (Moreira-Soto et al. 2016 ). The same findings were reported in hunting dogs (Kmetiuk et al. 2019 ) and dogs in areas with human rickettsiosis cases (Neves et al. 2023 ), both populations from Brazil. At the national level, Foley et al. ( 2019 ) and Palacios-Santana et al. ( 2023 ) demonstrated antibodies against Rickettsia SFG in dogs from Mexicali, Baja California, and Reynosa, Tamaulipas, respectively. Furthermore, Beristain-Ruiz et al. ( 2022 ) molecularly detected R . rickettsii (SFG) DNA in blood from dogs in Ciudad Juárez, Chihuahua. Finally, at a regional level, evidence of antibodies against Rickettsia SFG has been obtained in dogs from Mérida City (Dzul-Rosado et al. 2021 ). Using molecular diagnostic tests (PCR) and bioinformatics tools, Ojeda-Chi et al. ( 2019 ) and Arroyo-Ramírez et al. ( 2023 ) identified R . parkeri (SFG) in dogs from two localities of Yucatan. Our findings reinforce the previously formulated hypothesis that dogs can be sentinels for the epidemiological risk of zoonotic pathogens transmitted by arthropod vectors (including Rickettsia SFG) in humans who live nearby or coexist with them (Foley et al. 2019 ; Palacios-Santana et al. 2023 ; Neves et al. 2023 ). However, this study was not designed to prove or refute this hypothesis, so more research is necessary to understand the risk posed to people by having contact with or keeping dogs Rickettsia -SFG infected in their houses or premises. In this sense, it has been proved that dogs are amplifying hosts of some members of SFG, such as R . rickettsii , so they can transmit the bacteria to their ectoparasites and cause zoonotic transmission to humans or other domestic animals, as has been documented in some parts of the world (Binder et al. 2021 ; Beristain-Ruiz et al. 2022 ). The present study did not register the ectoparasite species that infested dogs. It is documented that dogs have contact with Rickettsia SFG through the vectorial via generated by several tick species (biological vectors), including Rhipicephalus linnaei ( = R . sanguineus sensu lato ) (Peniche-Lara et al. 2015b , 2018 ; Foley et al. 2019 ; Pacheco-Solano et al. 2019 ; Beristain-Ruiz et al. 2022 ; Salomon et al. 2022 ). This tick has an endophilic behavior, wide distribution, and large populations in regions with tropical climates from Mexico, such as the Yucatan Peninsula (Rodríguez-Vivas et al. 2016 ; 2023 ; Sánchez-Montes et al. 2021b ), so it is frequently found infesting dogs from localities with characteristics similar to this study (Peniche-Lara et al. 2015b ; 2018 ; Martínez-Ortiz et al. 2019 ; Ojeda-Chi et al. 2019 ). Other findings that explain Rickettsia SFG vectorial via are those of Vázquez-Guerrero et al. ( 2023 ), who evidenced DNA of R . amblyommatis and R . bellii (members of SFG) in ticks such as Amblyomma auriculatum , A . ovale , and A . mixtum collected in dogs from Yucatan. Finally, Martínez-Ortiz et al. ( 2019 ) found molecular evidence of Rickettsia sp. in ticks of various genera and species ( A . mixtum , R . sanguineus s. l., and Ixodes affinis ) collected from dogs in a locality of Yucatan whit history rickettsiosis outbreak among its inhabitants. Therefore, the authors suggest that those ectoparasites may have played a role in the zoonotic transmission of the bacteria. The presentation and distribution of diseases transmitted by ticks, such as SFG rickettsiosis, are influenced by complex demographic, ecological, environmental, and social factors, such as the population density of ticks and their hosts, including dogs (Torres-Castro et al. 2020 a). According to the multinomial model, dogs living in dwellings in the central area of Ucú have a lower risk (RR = 0.14, 95% CI 0.02–0.67) for Rickettsia SFG infection than those living in the other areas. Getting background information to compare our research is challenging due to the lack of previous studies using our sampling design or similar. We collected biological samples and data (variables) for risk infection analysis based on a convenient geographical division of the study site into concentric areas and a specific number of studied dwellings by area. So, this ‘spatial system’ for studying the infection of Rickettsia resulted in favorable findings of risk areas in mammal hosts from the study site. Dog-free access to the outside of the dwelling was not significant in the corresponding model. However, the protective value of the “interior area” variable can be partially explained by the behavior of wandering outside the dwelling, which, according to the data collected in the questionnaire (data not shown), was less frequent than in dogs from dwellings in the central and exterior areas, probably because these areas had less density of dwellings (field observation) limiting the owners to keep their dogs inside the premises. Wandering outside the dwelling has been associated with contact with Rickettsia SFG transmission scenarios, such as vacant lots, vegetated areas, unpaved roads, etc., where other dogs and hosts, including synanthropic and wild fauna, and Rickettsia SFG vectors, also circulate (Palacios-Santana et al. 2023 ). In this sense, Szabó et al. ( 2013 ) found a positive correlation between seropositivity against Rickettsia SFG in dogs with access to vegetated areas around the dwellings. It is relevant to mention that the dwellings in the exterior area of Ucú are surrounded by original vegetation (tropical deciduous forest) with areas of seasonal agriculture. Another aspect that helps explain the lower risk of Rickettsia SFG infection in dogs from the interior area of the study location is the veterinary care (vaccination and periodic deworming). It was observed that dogs from the interior area of Ucú received better veterinary care. Also, the lack of ectoparasite control was a frequent characteristic of dogs from dwellings in the central and exterior areas (data not shown). Lack of veterinary care has been associated with higher ectoparasite infestation levels (Ojeda-Chi et al. 2019 ), increasing the risk of Rickettsia transmission. Likewise, Forshey et al. ( 2010 ) point out that dogs that stay in their homes longer tend to receive better health care from their owners, considerably reducing their probability of being parasitized by ticks and the risk of Rickettsia infection. The snPCR showed the presence of Rickettsia TG and SFG in the rodents. Detecting Rickettsia in rodents such as M . musculus and R . rattus has been identified as a significant risk factor for the indirect transmission of these bacteria to humans (Forshey et al. 2010 ; Rungrojn et al. 2021 ). Only one species of Rickettsia TG, R . typhi , has been reported in small rodents captured in different localities in the state of Yucatan (Peniche-Lara et al. 2015a ; Torres-Castro et al. 2018 ; Sánchez-Montes et al. 2021a ). On the other hand, for Rickettsia SFG, serological positive reactions have been detected in serum samples of rodents from the city of Mérida (Dzul-Rosado et al. 2021 ). It is recognized that the most important competent vectors of Rickettsia TG in its classic transmission cycle are the fleas of small rodents ( Xenopsylla cheopis ) (Leulmi et al. 2014 ), so the contact of these animals with these bacteria has been confirmed in numerous studies carried out in endemic areas. For example, in rodents from Spain, Lledó et al. ( 2003 ) reported antibodies against R . typhi . The same findings were obtained by Mostorino et al. ( 2003 ) in rodents from the District of Puncha, Peru, where febrile cases compatible with murine typhus ( R . typhi ) were previously identified in the inhabitants. So, the authors pointed out the rodents as the possible amplifying bacteria hosts. In Mexico, Sánchez-Montes et al. ( 2019 )d pez-Pérez et al. (2022) molecularly identified R . typhi in rodents from Hidalgo and Baja California states, respectively. The multinomial analysis showed that rodents from dwellings where opossums were captured had a higher risk of Rickettsia TG infection. Although its participation as an amplifying host is not evident, these results represent new insights into the importance of opossums’ role in the transmission cycle of Rickettsia TG through its ectoparasites (Santoyo-Colín et al. 2021 ). The opossums captured in Ucú were not evaluated by snPCR to identify the Rickettsia groups. However, in the study region, there is serological evidence of contact among these animals with this Rickettsia group (Dzul-Rosado et al. 2021 ). As previously mentioned, the main reservoirs of Rickettsia TG are fleas of small rodents. However, evidence indicates that the cat flea Ctenocephalides felis may be the principal vector of an alternative cycle of R . typhi in anthropized environments such as Ucú (Eisen et al. 2012; Maina et al. 2016 ; Santoyo-Colín et al. 2021 ). This flea has an indirect life cycle that allows it to infest different mammalian hosts, including small rodents (Peniche-Lara et al. 2015a ) and opossums (Bezerra-Santos et al. 2021 ), which explains the positive correlation between the Rickettsia TG infection in the studied rodents with the presence of opossums. Like Rickettsia TG, rodents acquire infection with Rickettsia SFG through the bite of ectoparasites (vectorial via), mainly ticks. In this regard, it is known rodents are parasitized by several genera and species of hard ticks, including Amblyomma , Ixodes , and Rhipicephalus (Rodríguez-Vivas et al. 2016 ), which are reservoirs for several members of the SFG (López-Pérez et al. 2022 ). For this reason, records of rodents with Rickettsia SFG contact are numerous worldwide. For example, Milagres et al. ( 2013 ) and Quintero-Vélez et al. (2013) found antibodies against Rickettsia SFG in rodents captured in the state of Minas Gerais, Brazil, and in endemic areas of Antioquia, Colombia, respectively. In Mexico, R . rickettsii (SFG) was identified with molecular tools in biological samples of different species of rodents captured in several regions (Sosa-Gutiérrez et al. 2014 ). The multinomial GLM showed a higher risk (RR = 21; 95% CI 2.3–196) of Rickettsia SFG infection in rodents captured in dwellings where a dog infected by SFG occurs. This finding is relevant because it indicates that rodents and dogs could be involved in the same Rickettsia SFG transmission cycle. However, molecular and bioinformatic analyses of Rickettsia populations are necessary to prove this hypothesis. The relationship between rodents and dogs infected with SFG Rickettsia could be linked to several tick species having more than one host through the development cycle. For example, in the Amblyomma complex, ticks' immature stages infect rodents (Fernandes-Martins et al. 2016 ), and their adult stages infect larger mammals like dogs (Rodríguez-Vivas et al. 2016 ). In this context, it is known that the maintenance of some members of Rickettsia SFG is due to horizontal transmission. Therefore, all stages (larvae, nymph, and adult) can participate in the Rickettsia SFG transmission among susceptible hosts such as rodents and dogs (Moraes-Filho et al. 2018 ; Suwanbongkot et al. 2019 ). In a recent study, antibodies against Rickettsia SFG were determined in rodents and dogs from the same dwellings (Dzul-Rosado et al. 2021 ). Similarly, what was found in our analyses indicates that these animals are sharing Rickettsia transmission cycles through a possible exchange of vector ectoparasites (Issae et al. 2023 ). This study provides new evidence on the participation of dogs and rodents in the epidemiological cycles of Rickettsia groups circulating in the study area. Our findings suggest that these animals are involved in the same transmission cycle through ectoparasite exchange, mainly fleas and ticks. Statistical modeling reveals that the spatial location of the dwelling, the presence of infected dogs, and the presence of opossums in the same dwelling help as proxies of the risk of infection in the synanthropic rodents captured in the premises. Declarations Acknowledgements To the families of Ucú, Yucatán, for allowing us into their homes. To the National Council of Science and Technology of Mexico (CONACYT in Spanish) for the scholarship (no. 1089347) granted to one of the authors. To Dr. Rosa María Galaz Ávalos for the support for the fieldwork. Statement of Animal Ethics This study was approved by the Bioethics Committee of the Faculty of Veterinary Medicine of the Universidad Autónoma de Yucatán (UADY), Merida, Mexico (minute CB-CCBA-M-2021-003). The Ministry of Environment and Natural Resources (SEMARNAT in Spanish) of Mexico authorized the capture and extraction of rodents for scientific collection purposes (minute 31/K5-0108/12/20). Additionally, we followed the Guide for the Management of Wild Animals outlined by the American Society of Mammalogists (Sikes et al., 2016). The studied dogs were handled with owner consent and properly signed permits. Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Conflict of Interest Statement The authors have no relevant financial or non-financial interests to disclose. Author Contributions César Lugo-Caballero and Marco Torres-Castro performed conceptualization. Abigail Arroyo-Ramírez, César Lugo-Caballero, Enrique Reyes-Novelo, and Marco Torres-Castro performed the methodology. Enrique Reyes-Novelo, Jesús Alonso Panti-May, R. Iván Rodríguez-Vivas, and Marco Torres-Castro performed formal analysis and investigation. Writing - Abigail Arroyo-Ramírez, César Lugo-Caballero, Enrique Reyes-Novelo, and Marco Torres-Castro performed original draft preparation. César Lugo-Caballero and Marco Torres-Castro performed funding acquisition. Abigail Arroyo-Ramírez, Jesús Alonso Panti-May, Alejandro Suárez-Galaz, Tana Osorio-Primo, Hugo Ruiz-Piña, and Marco Torres-Castro performed resources. César Lugo-Caballero and Marco Torres-Castro performed supervision. All authors are reviewing, reading, and approving the final manuscript. References Arroyo-Ramírez A, Lugo-Caballero C, Bolio-González M, Rodríguez-Vivas RI, Reyes-Novelo E, Panti-May JA, Torres-Castro MA (2022) El género Rickettsia y reportes de infección en perros de Yucatán, México. 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Zoonoses Public Health 68:1–7. https://doi.org/10.1111/zph.12770 Sikes RS, Animal Care and Use Committee of the American Society of Mammalogists (2016) 2016 Guidelines of the American Society of Mammalogists for the use of wild mammals in research and education. J Mammal 97:663–688. https://doi.org/10.1093/jmammal/gyw078 Sosa-Gutiérrez CG, Vargas M, Torres J, Gordillo-Pérez G (2014) Tick-borne rickettsial pathogens in rodents from Mexico. J Biomedical Science and Engineering 7:884. https://doi.org/10.4236/jbise.2014.711087 Suwanbongkot C, Langohr IM, Harris EK, Dittmar W, Christofferson RC, Macaluso KR (2019) Spotted fever group Rickettsia infection and transmission dynamics in Amblyomma maculatum . Infect Immun 87:e00804-18. https://doi.org/10.1128/IAI.00804-18 Szabó MP, Pinter A, Labruna MB (2013) Ecology, biology and distribution of spotted-fever tick vectors in Brazil. Front Cell Infect Microbiol 3:27. https://doi.org/10.3389/fcimb.2013.00027 Thrusfield M (2007) Veterinary epidemiology. Blackwell, United Kingdom Torres-Castro M, Martínez-Ortiz D, Panti-May A, Koyoc-Cardeña E, López-Ávila K, Dzul-Rosado K, Zavala-Castro J, Chablé-Santos J, Manrique-Saide P (2018) Rickettsia typhi in rodents from a community with history of murine typhus from Yucatan, Mexico. Rev MVZ Cordoba 23:6974–6980. http://dx.doi.org/10.21897/rmvz.1420 Torres-Castro MA, Noh-Pech HR, Lugo-Caballero CI, Dzul-Rosado KR, Puerto FI (2020) Las enfermedades transmitidas por vector: importancia y aspectos epidemiológicos. Bioagrociencias 13:31–41. https://doi.org/10.56369/BAC.3446 Torres-Castro M, Reyes-Novelo E, Noh-Pech H, Tello-Martín R, Lugo-Caballero C, Dzul-Rosado K, Puerto-Manzano F, Rodríguez-Vivas RI (2020) Personal and household factors involved in recent Rickettsia exposure in a rural population from Yucatán, Mexico. Zoonoses Public Health 67:506–515. https://doi.org/10.1111/zph.12714 Torres-Castro M, Reyes-Novelo E, Noh-Pech H, Sánchez-Montes S, Colunga-Salas P, Lugo-Caballero C, Rodríguez-Vivas RI (2022a) Rickettsia rickettsii and Rickettsia typhi in inhabitants from a rural community of southeast Mexico. Rev Peru Med Exp Salud Publica 39:124–125. https://doi.org/10.17843/rpmesp.2022.391.10519 Torres-Castro M, Sánchez-Montes S, Colunga-Salas P, Noh-Pech H, Reyes-Novelo E, Rodríguez-Vivas RI (2022b) Molecular confirmation of Rickettsia parkeri in humans from Southern Mexico. Zoonoses Public Health 69:382–386. https://doi.org/10.1111/zph.12927 Torres-Castro M, Reyes-Novelo E, Bolio-González M, Lugo-Caballero C, Dzul-Rosado K, Colunga-Salas P, Sánchez-Montes S, Noh-Pech H., Puerto FI, Rodríguez-Vivas RI (2022c) Epidemiological study of the occurrence of typhus group Rickettsia natural infection in domiciliated dogs from a rural community in south-eastern Mexico. Animals 12:2885. https://doi.org/10.3390/ani12202885 Torres-Castro M, Reyes-Novelo E, Arroyo-Ramírez A, Lugo-Caballero C, Panti-May JA, Rodríguez-Vivas RI (2024) Actualización sobre aspectos epidemiológicos de la rickettsiosis en el trópico de México. Trop Subtrop Agroecosystems 27 https://doi.org/048.10.56369/tsaes.4942 Vázquez-Guerrero E, Reyes-Solís GC, Cano-Ravell AE, Machain-Williams C, Leyva-Gastélum M, Estrada-de Los Santos P, Álvarez-Hernández G, Ibarra JA (2023) Detection of Rickettsia amblyommatis and Rickettsia bellii in ticks collected from pet dogs in peri-urban and rural areas in Yucatan, Mexico. Exp Appl Acarol 90:441–453. https://dx.doi.org/10.1007/s10493-023-00825-z Verhoeve VI, Fauntleroy TD, Risteen RG, Driscoll TP, Gillespie JJ (2022) Cryptic genes for interbacterial antagonism distinguish Rickettsia species infecting blacklegged ticks from other Rickettsia pathogens. Front Cell Infect Microbiol 12:880813. https://doi.org/10.3389/fcimb.2022.880813 Additional Declarations No competing interests reported. Supplementary Files SF1.tif SF1. Photograph of polyacrylamide gels with positive products (p5, p6, p7, and p9) for Rickettsia SFG, obtained from blood samples of dogs from in Ucú, Yucatán, Mexico. c-: negative control, mm100bp: molecular weight marker, c+: positive control, p8: negative product. SF2.tif SF2. Photograph of polyacrylamide gels with positive products (p17, p23, p31, p34, p45, p58 and p62) for Rickettsia SFG, obtained from blood samples of dogs in Ucú, Yucatán, Mexico. c+: positive control, c-: negative control. Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-4451515","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":308928586,"identity":"c012ef42-fe40-45a1-a9c9-7ce917a92022","order_by":0,"name":"Abigail Arroyo-Ramírez","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Abigail","middleName":"","lastName":"Arroyo-Ramírez","suffix":""},{"id":308928587,"identity":"4c9e9a7c-1a03-46f2-871e-c20015f9960a","order_by":1,"name":"César Lugo-Caballero","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"César","middleName":"","lastName":"Lugo-Caballero","suffix":""},{"id":308928588,"identity":"098495a8-fe79-4416-ace2-0133334f1b16","order_by":2,"name":"Enrique Reyes-Novelo","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Enrique","middleName":"","lastName":"Reyes-Novelo","suffix":""},{"id":308928589,"identity":"88d43558-0e73-47f2-b4da-2c48274a3045","order_by":3,"name":"Henry Noh-Pech","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Henry","middleName":"","lastName":"Noh-Pech","suffix":""},{"id":308928590,"identity":"41a31001-8c8b-42b9-b94e-103fb7932216","order_by":4,"name":"Alejandro Suárez-Galaz","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Alejandro","middleName":"","lastName":"Suárez-Galaz","suffix":""},{"id":308928592,"identity":"748a8c33-0356-4a8f-9614-ac40f8576da8","order_by":5,"name":"Jesús Alonso Panti-May","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Jesús","middleName":"Alonso","lastName":"Panti-May","suffix":""},{"id":308928593,"identity":"443cec51-1527-474b-b597-fc942c958935","order_by":6,"name":"R. Iván Rodríguez-Vivas","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"R.","middleName":"Iván","lastName":"Rodríguez-Vivas","suffix":""},{"id":308928595,"identity":"07d7f3fe-6b3a-4552-bd58-9007915cc664","order_by":7,"name":"Tana Osorio-Primo","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Tana","middleName":"","lastName":"Osorio-Primo","suffix":""},{"id":308928597,"identity":"b2715829-c77a-432f-bb9f-3b6e8c849423","order_by":8,"name":"Hugo Ruiz-Piña","email":"","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":false,"prefix":"","firstName":"Hugo","middleName":"","lastName":"Ruiz-Piña","suffix":""},{"id":308928598,"identity":"00a478f6-c6d8-46f0-8254-2a65e5a8bd87","order_by":9,"name":"Marco Torres-Castro","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABE0lEQVRIie3SsUrDQBjA8S8cXpZP41gpNK9wIaPRvkpCIF07OnaKi61rDl9C8AUiB+0SdT2Jg6HgfKPgDaYtFmsS1E3k/tPlLj8+LgTAZPqzse0q+LSbd71ONgQ3T8lPCWyJ+J44V5e3y/E4gKE9fVFKP7hO/656ViDcAxnu3WCT9J4E8TOWAOLC5zwtPT4b+V4GwuMypI9ZyxgZ0z4yAdhLCNmflCEraL0DwrquiVRN4e4Qre9XxH6ryXBNwiZhOwRovp5CahJ1TfFk7PvIEsRiTqxpGnv8gpKjjI1iXlRp210GMqqWqIOBfZ4SeNWnroPUUurs+GS2iOdlyxf76OvR6n84jCbdoD0n/60wmUym/9k7Lw1f+IlUrxUAAAAASUVORK5CYII=","orcid":"","institution":"Universidad Autónoma de Yucatán","correspondingAuthor":true,"prefix":"","firstName":"Marco","middleName":"","lastName":"Torres-Castro","suffix":""}],"badges":[],"createdAt":"2024-05-21 01:40:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4451515/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4451515/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":58018647,"identity":"52db376a-52cf-48d0-b024-cd09c8f87707","added_by":"auto","created_at":"2024-06-10 04:22:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":823314,"visible":true,"origin":"","legend":"\u003cp\u003eMap of Mexico (A), Yucatan (B), and Ucú (C) showing the three areas dividing the study site (interior, central, and exterior) and the distribution of sampled dwellings.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4451515/v1/6755e245e506447901ed0906.png"},{"id":58019080,"identity":"83073418-58ba-4f6e-b3aa-8d4c1143a415","added_by":"auto","created_at":"2024-06-10 04:38:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1567201,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4451515/v1/7873ba7f-8b98-444c-902d-817f95316eb1.pdf"},{"id":58018649,"identity":"633d9ba1-2e6f-43be-91c8-a9c16ae95033","added_by":"auto","created_at":"2024-06-10 04:22:13","extension":"tif","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16016328,"visible":true,"origin":"","legend":"\u003cp\u003eSF1. Photograph of polyacrylamide gels with positive products (p5, p6, p7, and p9) for Rickettsia SFG, obtained from blood samples of dogs from in Ucú, Yucatán, Mexico. c-: negative control, mm100bp: molecular weight marker, c+: positive control, p8: negative product.\u003c/p\u003e","description":"","filename":"SF1.tif","url":"https://assets-eu.researchsquare.com/files/rs-4451515/v1/1373fd7b48b17e613a7a557e.tif"},{"id":58018648,"identity":"1fc23105-3519-4287-9976-7cb77e89ed2f","added_by":"auto","created_at":"2024-06-10 04:22:13","extension":"tif","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":14586854,"visible":true,"origin":"","legend":"\u003cp\u003eSF2. Photograph of polyacrylamide gels with positive products (p17, p23, p31, p34, p45, p58 and p62) for \u003cem\u003eRickettsia\u003c/em\u003e SFG, obtained from blood samples of dogs in Ucú, Yucatán, Mexico. c+: positive control, c-: negative control.\u003c/p\u003e","description":"","filename":"SF2.tif","url":"https://assets-eu.researchsquare.com/files/rs-4451515/v1/81d23c41b7dadc2149fab9df.tif"}],"financialInterests":"No competing interests reported.","formattedTitle":"Epidemiological factors associated with the spatial distribution of two Rickettsia hosts in a locality of Yucatán, Mexico","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRickettsioses is a group of infectious diseases caused by the genera \u003cem\u003eOrientia\u003c/em\u003e and \u003cem\u003eRickettsia\u003c/em\u003e bacteria. They are transmitted through the bite or feces of hematophagous ectoparasites such as ticks, lice, fleas, and mites (Gillespie and Salje \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). According to its genomic characteristics, \u003cem\u003eRickettsia\u003c/em\u003e includes five groups: 1) \u003cem\u003eBellii\u003c/em\u003e, 2) transitional, 3) typhus (TG), 4) \u003cem\u003eTamurae\u003c/em\u003e/\u003cem\u003eIxodes\u003c/em\u003e, and 5) spotted fever (SFG) (Verhoeve et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRickettsiosis caused by \u003cem\u003eRickettsia\u003c/em\u003e shows a wide range of prevalence and incidence rates across different regions of Mexico. According to S\u0026aacute;nchez-Montes et al. (\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e) and Torres-Castro et al. (\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), the prevalence of this bacteria genus is higher in the northern and southeastern states of the country. In inhabitants from the Yucatan peninsula, southeastern Mexico, some species belonging to the SFG, such as \u003cem\u003eR\u003c/em\u003e. \u003cem\u003erickettsii\u003c/em\u003e (Torres-Castro et al \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2022a\u003c/span\u003e)d \u003cem\u003eparkeri\u003c/em\u003e (Peniche-Lara and Lara-Perera \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2022b\u003c/span\u003e), and belonging to TG, such as \u003cem\u003eR\u003c/em\u003e. \u003cem\u003etyphi\u003c/em\u003e, have been found (Torres-Castro et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2022a\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe zoonotic foci of \u003cem\u003eRickettsia\u003c/em\u003e SFG and TG, including mammal hosts or ectoparasites vectors, have not been figured out (Torres-Castro et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, certain biotic and abiotic factors increase the risk of contact or infection with \u003cem\u003eRickettsia\u003c/em\u003e groups in localities of Yucatan state. These factors include a younger age for people living in rural localities, having peridomestic family gardens (orchards), and the presence of free-living vector arthropods in the peridomicile (Torres-Castro et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2020\u003c/span\u003eb). Similarly, households with at least one case of human rickettsiosis recorded the presence of animals positive for \u003cem\u003eRickettsia\u003c/em\u003e SFG or TG (Dzul-Rosado et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). These last findings suggest the potential role of dogs (companion animals), rodents, and other synanthropic animals in the transmission cycles of \u003cem\u003eRickettsia\u003c/em\u003e (Torres-Castro et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDogs and rodents are hosts of several pathogenic \u003cem\u003eRickettsia\u003c/em\u003e species, taking part in their epidemiological cycles' transmission, maintenance, and dispersion (Moreira-Soto et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; S\u0026aacute;nchez-Montes et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e; Arroyo-Ram\u0026iacute;rez et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In Yucatan, these animals are hosts of pathogenic species, such as \u003cem\u003eR\u003c/em\u003e. \u003cem\u003efelis\u003c/em\u003e (Panti-May et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), R. \u003cem\u003etyphi\u003c/em\u003e (Peniche-Lara et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015a\u003c/span\u003e; Mart\u0026iacute;nez-Ortiz et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2018\u003c/span\u003e)d \u003cem\u003eparkeri\u003c/em\u003e (Ojeda-Chi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Arroyo-Ram\u0026iacute;rez et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), and also for several species of \u003cem\u003eRickettsia\u003c/em\u003e vector ectoparasites (Peniche-Lara et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015a\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003eb\u003c/span\u003e; Mart\u0026iacute;nez-Ortiz et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ojeda-Chi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe spatial distribution of these host animals is a relevant feature for the understanding of the \u003cem\u003eRickettsia\u003c/em\u003e infection risk, particularly in inhabited areas (Quintero et al. 2018; Torres-Castro et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e; Arroyo-Ram\u0026iacute;rez et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Recent studies that explored the spatial distribution of arthropod vectors and rickettsial hosts reveal that infection tends to occur in spatial clusters where mammal hosts and ectoparasitic arthropods converge (Dzul-Rosado et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, the generalized distribution of companion animals like dogs and synanthropic fauna and their ectoparasites in human settlements makes it challenging to understand \u003cem\u003eRickettsia\u003c/em\u003e infection risk. This study aims to identify the frequency of \u003cem\u003eRickettsia\u003c/em\u003e SFG and TG infection in the studied animals, to determine the spatial distribution of the hosts, and to identify the factors associated with the infection risk at locality scale.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy site\u003c/h2\u003e \u003cp\u003eThe study was conducted in the locality of Uc\u0026uacute; (22\u0026deg;01\u0026prime;55\u0026Prime; N, 89\u0026deg;44\u0026prime;47\u0026Prime; W), located in the state of Yucatan, Mexico, in the municipality of the same name (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The municipality has a territorial total area of 130.8 km\u003csup\u003e2\u003c/sup\u003e and an average altitude of 8 m above sea level. Uc\u0026uacute; is part of the metropolitan area of Merida City, which is the capital of Yucatan (INAFED 2021). The study site has a population of approximately 4,049 residents who live in 1,139 dwellings within the town (INEGI 2020).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe region has a warm, subhumid climate with summer rainfall. The average annual temperature is 26\u0026deg; C, and rainfall is 800 mm (INAFED 2021). The original vegetation includes low deciduous forests surrounded by patches of secondary and introduced vegetation, such as pastures for cutting and forage and temporary agriculture, as well as infrastructure such as dwellings, warehouses, parks, roads, and streets (Quiroz-Carranza and Orellana 2007).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eThe study design was descriptive and cross-sectional. Due to the sanitary restrictions caused by the CoViD-19 pandemic, the sample size was obtained based on the number of occupied dwellings (1,139) with the formula to calculate a sample size to estimate a frequency (Thrusfield \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), using a confidence level of 95%, precision of 80%, and expected proportion of 6% of animal captures accordingly with previous studies in the region (Panti-May et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo cover the total extension of the study site, two imaginary lines that crossed its center were drawn to divide it into three concentric areas (interior, central, and exterior). For a homogeneous distribution of the dwellings, sixteen per area for 48 total dwellings throughout the study site were considered (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Dwellings were selected by convenience, and those whose owners signed informed consent to participate in the study were included in the sample.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eBiological samples\u003c/h2\u003e \u003cp\u003eFrom August to October 2021, a single visit to each dwelling was carried out. Puppies\u0026thinsp;\u0026lt;\u0026thinsp;2 months of age and dogs that had received antibiotic treatment at least two months before the visit, according to the information provided by the owner, were excluded.\u003c/p\u003e \u003cp\u003eBefore blood sampling, the venipuncture skin area was sanitized with iodine and hydrogen peroxide to prevent cross-contamination with ectoparasite feces. Each dog's peripheral blood sample (up to 5 ml) was collected through femoral or cephalic vein puncture using 5 ml sterile syringes (BD Plastipak, Mexico) and placed in tubes with heparin (BD Vacutainer\u0026reg; PST, USA). During fieldwork, the samples were kept in portable iceboxes with refrigerants. All samples were then transferred to the laboratory to be centrifuged at 1,500 g for 10 min at room temperature to separate the plasma stored in a 1.8 ml microcentrifuge tube (Eppendorf\u0026reg;, USA) at -80\u0026deg; C until diagnostic procedures.\u003c/p\u003e \u003cp\u003eTen Sherman traps (8 x 23 x 9 cm; HB Sherman Traps Inc.\u0026reg;; USA) per dwelling were used to capture rodents. Traps were baited with oat flakes and artificial vanilla flavoring and placed only in the peridomicile area for two consecutive nights, resulting in a total capture effort of 960 nights/trap.\u003c/p\u003e \u003cp\u003eThe captured rodents were transported to the laboratory facilities for further processing. Rodent species using field guides were identified (Reid \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). All rodents were anesthetized with isoflurane (Piramal Enterprises Limited\u0026reg;; United Kingdom) and euthanized with an overdose (90\u0026ndash;210 mg/kg) of pentobarbital sodium (Aranda\u0026reg;; Mexico). After euthanasia, the abdominal cavity was opened, and the spleen was collected and stored in 1.8 ml microcentrifuge tubes at -80\u0026deg; C.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eAnimal data collection\u003c/h2\u003e \u003cp\u003eDog data was collected by applying a questionnaire to each animal's owner on the day of blood sampling and visually inspecting the animals. The data collected included information on the sex (male or female) and age (puppy: \u0026lt; 1 year, adult: 1 to 6 years, or geriatric: \u0026ge; 6 years [Torres-Castro et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e]). Additionally, the study examined whether the animals were recently infested with ticks or fleas (positive [yes] or negative [no], regardless of the number of ectoparasites) and the level of infestation (regardless of the type of ectoparasite [tick or flea]). Infestation levels assessed by visual inspection were classified as negative (no presence of ectoparasites), mild (\u0026le;\u0026thinsp;10 ectoparasites), moderate (11 to 30 ectoparasites), or severe (\u0026gt;\u0026thinsp;30 ectoparasites) (Torres-Castro et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e). Lastly, the study also considered whether the animals had access to roam outside the dwelling (yes or no, regardless of time).\u003c/p\u003e \u003cp\u003eRodent data was collected on sex (male or female), age (adult or juvenile), weight (\u0026le;\u0026thinsp;10 g or \u0026gt;\u0026thinsp;10 g), and reproductive conditions (active or inactive) (Panti-May et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eDwelling data collection\u003c/h2\u003e \u003cp\u003eThe questionnaire also gathered information on dwelling characteristics, location (interior, central, and exterior), the presence/absence of 1) companion animals other than dogs (e.g., cats, rabbits, etc.), 2) production animals (e.g., cattle, goats, sheep, horses, and poultry), and 3) synanthropic fauna (rodents or opossums). To monitor the presence/absence of opossums (\u003cem\u003eDidelphis\u003c/em\u003e sp.), a Tomahawk trap (23 x 23 x 66 cm, Tomahawk Live Trap Inc.\u0026reg;, USA) was placed per dwelling, along potential routes passing (e.g., fences, fruit trees, orchards). Traps were baited with seasonal fruit and kept open during the same consecutive nights of rodent trapping, resulting in a total capture effort of 96 nights/trap. All captured opossums were released in the nearest forested area to the study locality.\u003c/p\u003e \u003cp\u003e \u003cb\u003eGenomic DNA extraction and identification of\u003c/b\u003e \u003cb\u003eRickettsia\u003c/b\u003e \u003cb\u003egroups\u003c/b\u003e\u003c/p\u003e \u003cp\u003eGenomic DNA was extracted from blood samples and spleens using the Wizard Genomic DNA Purification Kit\u0026reg; (Promega\u0026reg;, USA). The extracted DNA was then assessed for its quality (A260/280) and concentration (ng/\u0026micro;l) using a Nanodrop\u0026trade; (Thermofisher Scientific\u0026trade;, USA). Subsequently, the DNA samples were stored at -20\u0026deg; C until used to detect \u003cem\u003eRickettsia\u003c/em\u003e DNA.\u003c/p\u003e \u003cp\u003eTo identify \u003cem\u003eRickettsia\u003c/em\u003e groups (SFG and TG), a semi-nested multiplex PCR (snPCR) targeting a fragment of \u003cem\u003esca5\u003c/em\u003e, which encodes a fragment of the outer membrane protein B (omp B) in all \u003cem\u003eRickettsia\u003c/em\u003e members, was performed. In the first round, the oligonucleotides \u003cem\u003erOmpB OF\u003c/em\u003e (5\u0026rsquo;-GTAACCGGAAGTAATCGTTTCGTAA-3\u0026rsquo;), \u003cem\u003erOmpB OR\u003c/em\u003e (5\u0026rsquo;-GCTTTATAACCAGCTAAACCACC-3\u0026rsquo;) (Choi et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), and \u003cem\u003erOmpB-804 Fw TG\u003c/em\u003e (5\u0026rsquo;-GAATCAACTGATACAGCAGC-3\u0026rsquo;) were used. In the second, the oligonucleotides \u003cem\u003erOmpB SFG IF\u003c/em\u003e (5'-GTTTAATACGTGCTGCTAACCAA-3'), \u003cem\u003erOmpB SFG/TG IR\u003c/em\u003e (5'-GGTTTGGCCCATATACCATAAG-3') (Choi et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), and \u003cem\u003erOmpB TG IF\u003c/em\u003e (5'-AAGATCCTTCTGATGTTGCAACA-3') were used.\u003c/p\u003e \u003cp\u003eFor the first round, initial denaturation at 95\u0026deg;C for 5 min was followed by 35 cycles of denaturation at 95\u0026deg;C for 15 sec, alignment at 54\u0026deg;C for 15 sec, extension at 72\u0026deg;C for 30 sec, and a final extension of 72\u0026deg;C for 3 min. The same conditions were used for the second round, but the alignment temperature was changed to 56\u0026deg;C. The final extension was conducted at 72\u0026deg; C for 3 min (Arroyo-Ram\u0026iacute;rez et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDue to the low genetic similarity between these two \u003cem\u003eRickettsia\u003c/em\u003e groups, this snPCR produces amplified fragments of two sizes: 420 base pairs (bp) for the SFG and 237 bp for the TG (Choi et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Previously characterized positive controls were used to confirm that the reactions were done correctly (Torres-Castro et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2020\u003c/span\u003eb, c). The negative control was the PCR mixture without any template DNA. Electrophoresis was performed in 10% polyacrylamide gels (Sigma-Aldrich Products\u0026reg;, Germany) deposited in vertical cameras (Bio-Rad Laboratories\u0026reg;, USA) and stained with 1.1 molar silver nitrate. For the final visualization and recording of the results, a UV light transilluminator was used (Hoefer\u0026reg;, USA). The sample that showed amplification was considered positive for \u003cem\u003eRickettsia\u003c/em\u003e infection.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics were used to analyze snPCR results and determine \u003cem\u003eRickettsia\u003c/em\u003e infection frequencies and percentages in the studied animals. The Clopper-Pearson procedure estimated 95% confidence intervals (CI) using the Quantitative Parasitology package for R (R\u0026oacute;zsa et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Reiczigel et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA Fisher's exact test was used to determine the statistical association between the frequency of infected animals and the surveyed variables related to biological or dwelling characteristics. Those associations with a p\u0026thinsp;\u0026lt;\u0026thinsp;0.3 were considered significant for inclusion as independent variables in the modeling analyses with generalized linear models.\u003c/p\u003e \u003cp\u003eA generalized linear model (GLM) with binomial error distribution was used to select predictor variables for the risk of \u003cem\u003eRickettsia\u003c/em\u003e infection in dogs. The dependent variable for the dog's data was the animal's status according to snPCR results (positive or negative for infection with SFG). The rodent\u0026rsquo;s data was analyzed by a multinomial GLM using the dependent variable of the infection group with three levels: 1) \"Not infected\" or \"negative,\" 2) \"SFG infected,\" and 3) \"TG infected.\" The \"negative\" level was used as a reference. Akaike\u0026rsquo;s information criterion was used to select the best-fit model. The statistical significance was set at a p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. The relative risk (RR) and a 95% confidence interval (CI) were estimated. R software version 3.9.0 in the RStudio programming environment helped with the statistical analyses (R Core Team \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eOne hundred animals were studied; 64% were dogs, and 36% were rodents.\u003c/p\u003e \u003cp\u003eOf the studied dogs, 57.8% (37/64) were males and 42.2% (27/64) were females. About age, 21.8% (14/64) were puppies, 67.2% (43/64) were adults, and 10.9% (7/64) were geriatric. The results showed that 29.7% (19/64) had fleas, and 75% (48/64) had ticks. The infestation levels, regardless of the type of ectoparasite (fleas or ticks), were distributed as follows: 7.8% (5/64) had no infestations, 67.2% (43/64) had mild infestations, 20.3% (13/64) had moderate infestations, and 4.7% (3/64) had severe infestations. Moreover, 73.4% (47/64) of the studied dogs had free access to roam outside the dwelling and its peridomicile (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\u003eFrequency of \u003cem\u003eRickettsia\u003c/em\u003e SFG infection and the characteristics of the dogs and dwellings of Uc\u0026uacute;, Yucatan, Mexico, and its respective \u003cem\u003eP\u003c/em\u003e-value from the Fisher\u0026rsquo;s exact test for the predictor variable selection.\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\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDogs (%)\u003c/p\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;64\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSFG (%)\u003c/p\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;18\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDog characteristics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003cp\u003eMale\u003c/p\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37 (57.8)\u003c/p\u003e \u003cp\u003e27 (42.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (50)\u003c/p\u003e \u003cp\u003e9 (50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003cp\u003ePuppy\u003c/p\u003e \u003cp\u003eAdult\u003c/p\u003e \u003cp\u003eGeriatric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14 (21.8)\u003c/p\u003e \u003cp\u003e43 (67.2)\u003c/p\u003e \u003cp\u003e7 (10.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (33.3)\u003c/p\u003e \u003cp\u003e9 (50)\u003c/p\u003e \u003cp\u003e3 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.18*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlea infestation\u003c/p\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (29.7)\u003c/p\u003e \u003cp\u003e45 (70.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (16.7)\u003c/p\u003e \u003cp\u003e15 (83.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.22*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTick infestation\u003c/p\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48 (75)\u003c/p\u003e \u003cp\u003e16 (25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 (83.3)\u003c/p\u003e \u003cp\u003e3 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInfestation level\u003c/p\u003e \u003cp\u003eNull\u003c/p\u003e \u003cp\u003eMild\u003c/p\u003e \u003cp\u003eModerate\u003c/p\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (7.8)\u003c/p\u003e \u003cp\u003e43 (67.2)\u003c/p\u003e \u003cp\u003e13 (20.3)\u003c/p\u003e \u003cp\u003e3 (4.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (5.6)\u003c/p\u003e \u003cp\u003e12 (66.7)\u003c/p\u003e \u003cp\u003e4 (22.2)\u003c/p\u003e \u003cp\u003e1 (5.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAccess to roam\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e47 (73.4)\u003c/p\u003e \u003cp\u003e17 (26.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 (83.3)\u003c/p\u003e \u003cp\u003e3 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDwelling characteristics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003cp\u003eInterior\u003c/p\u003e \u003cp\u003eCentral\u003c/p\u003e \u003cp\u003eExterior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (29.7)\u003c/p\u003e \u003cp\u003e19 (29.7)\u003c/p\u003e \u003cp\u003e26 (40.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (11.1)\u003c/p\u003e \u003cp\u003e6 (33.3)\u003c/p\u003e \u003cp\u003e10 (55.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.11*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProduction animals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40 (62.5)\u003c/p\u003e \u003cp\u003e24 (37.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 (61.1)\u003c/p\u003e \u003cp\u003e7 (38.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCompanion animals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e56 (87.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17 (94.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (12.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (5.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSynanthropic animals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36 (56.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (66.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.17*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28 (43.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (33.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRodents\u003c/p\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 (46.9)\u003c/p\u003e \u003cp\u003e34 (53.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (55.6)\u003c/p\u003e \u003cp\u003e8 (44.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOpossums\u003c/p\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (25)\u003c/p\u003e \u003cp\u003e48 (75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (16.7)\u003c/p\u003e \u003cp\u003e15 (83.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e*\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.3\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eRegarding the characteristics of the dwellings, 29.7% (19/64) of sampled dogs were from dwellings in the interior area, the same amount from the central area, and 40.6% (26/64) of dogs were from dwellings of the exterior area; 62.5% (40/64) of the sampled dogs coincided with at least one production animal; 87.5% (56/64) coincided with companion animals different from dogs; 46.9% (30/64) were sampled in dwellings with rodents, and 25% (16/64) of the studied dogs were from dwellings with opossums (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the captured rodents, 88.9% (32/36) were \u003cem\u003eMus musculus\u003c/em\u003e, 8.3% (3/36) were \u003cem\u003ePeromyscus yucatanicu\u003c/em\u003es, and 2.8% (1/36) were \u003cem\u003eOtotylomys phyllotis\u003c/em\u003e. Among them, 66.7% (24/36) were males and 33.3% (12/36) were females. The adult rodents were 86.1% (31/36), and juveniles were 13.9% (5/36).\u003c/p\u003e \u003cp\u003e According to the dwellings\u0026rsquo; characteristics, 27.8% (10/36) of the rodents were captured in the interior area, 16.7% (6/36) in the central area, and 55.6% (20/36) in the exterior area; 58.3% of rodents (21/36) were from dwellings with at least one production animal and 80.6% (29/36) were from dwellings with companion animals. Records of opossum presence were for 16.7% (6/36) of captured rodents.\u003c/p\u003e \u003cp\u003esnPCR testing revealed \u003cem\u003eRickettsia\u003c/em\u003e DNA in 28.1% (18/64, 95% CI 17.6%-40.8%) of dogs and 27.8% (10/36, 95% CI 14.2%-45.2%) rodents.\u003c/p\u003e \u003cp\u003eAll \u003cem\u003eRickettsia\u003c/em\u003e-positive dogs were for SFG. The distribution of these dogs was equal between females and males (50%, 9/18); 50% (9/18) were adults, 33.3% (6/18) were puppies, and 16.7% (3/18) were geriatrics (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eOf the \u003cem\u003eRickettsia\u003c/em\u003e-positive rodents, 90% (9/10) were \u003cem\u003eM\u003c/em\u003e. \u003cem\u003emusculus\u003c/em\u003e and 10% (1/10) were \u003cem\u003eP\u003c/em\u003e. \u003cem\u003eyucatanicus\u003c/em\u003e; 70% (7/10) were positive for SFG, including the individual \u003cem\u003eP\u003c/em\u003e. \u003cem\u003eyucatanicus\u003c/em\u003e, while 30% (3/10) were positive for TG, all of which were \u003cem\u003eM\u003c/em\u003e. \u003cem\u003emusculus\u003c/em\u003e. Among these infected rodents, 80% (8/10) were male and 20% (2/10) were female. Additionally, 80% (8/10) were adults, and 20% (2/10) were juveniles (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Finally, 16.7% (6/36) of the captured rodents coincided with at least one dog with \u003cem\u003eRickettsia\u003c/em\u003e infection.\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\u003eFrequency of \u003cem\u003eRickettsia\u003c/em\u003e SFG and TG infection detected by multiplex semi-nested polymerase chain reaction concerning the characteristics of the rodents and dwellings from Uc\u0026uacute;, Yucatan, Mexico, and their respective \u003cem\u003eP\u003c/em\u003e-value returned by the Fisher\u0026rsquo;s exact test for the selection of the predictor variables.\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\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eSFG (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTG (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRodents\u0026rsquo; characteristics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003cp\u003eMale\u003c/p\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e6 (85.7)\u003c/p\u003e \u003cp\u003e1 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003cp\u003eJuvenil\u003c/p\u003e \u003cp\u003eAdult\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e1 (14.3)\u003c/p\u003e \u003cp\u003e6 (85.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight (gr)\u003c/p\u003e \u003cp\u003e\u0026lt; 10\u003c/p\u003e \u003cp\u003e\u0026gt; 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e1 (14.3)\u003c/p\u003e \u003cp\u003e6 (85.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.23*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eReproductive condition\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003cp\u003eActive\u003c/p\u003e \u003cp\u003eInactive\u003c/p\u003e \u003cp\u003eFemale\u003c/p\u003e \u003cp\u003eActive\u003c/p\u003e \u003cp\u003eInactive\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e6 (85.7)\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e1 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDwellings\u0026rsquo; characteristics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDwelling location\u003c/p\u003e \u003cp\u003eInterior\u003c/p\u003e \u003cp\u003eCentral\u003c/p\u003e \u003cp\u003eExterior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e1 (14,3)\u003c/p\u003e \u003cp\u003e2 (28,6)\u003c/p\u003e \u003cp\u003e4 (57,1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e3 (100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProduction animals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e5 (71.4)\u003c/p\u003e \u003cp\u003e2 (28.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOther companion animals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e6 (85.7)\u003c/p\u003e \u003cp\u003e1 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOpossums\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e1 (14.3)\u003c/p\u003e \u003cp\u003e6 (85.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2 (66.7)\u003c/p\u003e \u003cp\u003e1 (33.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.07*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDogs with Rickettsia spp.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c7\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e4 (57.1)\u003c/p\u003e \u003cp\u003e3 (42.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.007*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e3/3 (100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e*\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.3\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe exploratory bivariate analyses showed statistical associations between infected dogs with \u003cem\u003eRickettsia\u003c/em\u003e SFG with age, flea infestation, dwelling location, and presence of synanthropic animals (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In contrast, the best predictor variables for the presence of \u003cem\u003eRickettsia\u003c/em\u003e infection in rodents were 1) the presence of opossums for TG \u003cem\u003eRickettsia\u003c/em\u003e and 2) the presence of SFG-infected dogs for SFG \u003cem\u003eRickettsia\u003c/em\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe final binomial GLM with the smallest AIC value (76.33) for SFG-infected dogs included the predictor variables \u0026ldquo;dwelling location\u0026rdquo; and \u0026ldquo;other companion animals.\u0026rdquo; The model showed that dogs from the interior area have a lower risk (RR\u0026thinsp;=\u0026thinsp;0.14; 95% CI 0.02\u0026ndash;0.65) of \u003cem\u003eRickettsia\u003c/em\u003e SFG infection than dogs from the other areas (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of the best Generalized Linear Model with binomial error distribution to identify the risk ratio (RR) and its 95% confidence intervals (CI) of \u003cem\u003eRickettsia\u003c/em\u003e Spotted Fever Group (SFG) infection in the studied dog population from Uc\u0026uacute;, Yucatan, Mexico.\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\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.13\u0026ndash;1.88\u003c/p\u003e \u003cp\u003e0.02\u0026ndash;0.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExterior\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\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCentral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInterior\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOther companion animals\u003c/p\u003e \u003cp\u003eAbsence\u003c/p\u003e \u003cp\u003ePresence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e--\u003c/p\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.77\u0026ndash;115.2\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\u003eThe multinomial model with the lowest AIC value (53.68) showed a higher risk of \u003cem\u003eRickettsia\u003c/em\u003e TG infection (RR\u0026thinsp;=\u0026thinsp;14; 95% CI 0.95\u0026ndash;206) in rodents captured in dwellings with presence of opossum and a higher risk of \u003cem\u003eRickettsia\u003c/em\u003e SFG infection (RR\u0026thinsp;=\u0026thinsp;21; 95% CI 2.3\u0026ndash;196) in rodents captured in dwellings with presence of an SFG-infected dog (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of the multinomial stratified model to identify the risk ratio (RR) and its 95% confidence intervals (CI) of \u003cem\u003eRickettsia\u003c/em\u003e Spotted Fever Group (SFG) and Typhus Group (TG) infection in the studied rodent populations of Uc\u0026uacute;, Yucatan, Mexico.\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\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence of opossums\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNegative\u003c/p\u003e \u003cp\u003eTG\u003c/p\u003e \u003cp\u003eSFG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e--\u003c/p\u003e \u003cp\u003e0.05*\u003c/p\u003e \u003cp\u003e0.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14\u003c/p\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.95\u0026ndash;206\u003c/p\u003e \u003cp\u003e0.24\u0026ndash;51.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePresence of SFG-infected dogs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNegative\u003c/p\u003e \u003cp\u003eTG\u003c/p\u003e \u003cp\u003eSFG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e--\u003c/p\u003e \u003cp\u003e0.93\u003c/p\u003e \u003cp\u003e0.008*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003cem\u003ee\u003c/em\u003e\u003csup\u003e\u0026minus;\u0026thinsp;62\u003c/sup\u003e-1.6\u003cem\u003ee\u003c/em\u003e\u003csup\u003e+\u0026thinsp;56\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e2.3\u0026ndash;196\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e*\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn southeastern Mexico, studies that report \u003cem\u003eRickettsia\u003c/em\u003e TG and SFG infection have been conducted in rodents (Peniche-Lara et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015a\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Arroyo-Ram\u0026iacute;rez et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and dogs (Mart\u0026iacute;nez-Ortiz et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e; Arroyo-Ram\u0026iacute;rez et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, knowledge about the biotic or abiotic factors that influence the transmission and infection in these animals is limited (Ojeda-Chi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, the results of this research contribute to the understanding of the epidemiological elements involved in the transmission dynamics of these vector-borne bacteria, which are important for public health because of their capacity to generate outbreaks (Torres-Castro et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; S\u0026aacute;nchez-Montes et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e; Carrasquilla et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe snPCR performed in the studied dogs only revealed the infection of \u003cem\u003eRickettsia\u003c/em\u003e SFG, which differs from the reported by Torres-Castro et al. (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2022c\u003c/span\u003e) in dogs from Maxcan\u0026uacute;, Yucatan, infected with \u003cem\u003eRickettsia\u003c/em\u003e TG. However, it is essential to mention that the sampling months are different, influencing the abundance and richness of vector ectoparasites (Rodr\u0026iacute;guez-Vivas et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Contact of dogs with \u003cem\u003eRickettsia\u003c/em\u003e SFG has been documented in several countries with endemic areas. For example, antibodies against this \u003cem\u003eRickettsia\u003c/em\u003e group were found in dogs from Costa Rica (Moreira-Soto et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The same findings were reported in hunting dogs (Kmetiuk et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and dogs in areas with human rickettsiosis cases (Neves et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), both populations from Brazil.\u003c/p\u003e \u003cp\u003eAt the national level, Foley et al. (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and Palacios-Santana et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) demonstrated antibodies against \u003cem\u003eRickettsia\u003c/em\u003e SFG in dogs from Mexicali, Baja California, and Reynosa, Tamaulipas, respectively. Furthermore, Beristain-Ruiz et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) molecularly detected \u003cem\u003eR\u003c/em\u003e. \u003cem\u003erickettsii\u003c/em\u003e (SFG) DNA in blood from dogs in Ciudad Ju\u0026aacute;rez, Chihuahua. Finally, at a regional level, evidence of antibodies against \u003cem\u003eRickettsia\u003c/em\u003e SFG has been obtained in dogs from M\u0026eacute;rida City (Dzul-Rosado et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Using molecular diagnostic tests (PCR) and bioinformatics tools, Ojeda-Chi et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and Arroyo-Ram\u0026iacute;rez et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) identified \u003cem\u003eR\u003c/em\u003e. \u003cem\u003eparkeri\u003c/em\u003e (SFG) in dogs from two localities of Yucatan.\u003c/p\u003e \u003cp\u003eOur findings reinforce the previously formulated hypothesis that dogs can be sentinels for the epidemiological risk of zoonotic pathogens transmitted by arthropod vectors (including \u003cem\u003eRickettsia\u003c/em\u003e SFG) in humans who live nearby or coexist with them (Foley et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Palacios-Santana et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Neves et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, this study was not designed to prove or refute this hypothesis, so more research is necessary to understand the risk posed to people by having contact with or keeping dogs \u003cem\u003eRickettsia\u003c/em\u003e-SFG infected in their houses or premises. In this sense, it has been proved that dogs are amplifying hosts of some members of SFG, such as \u003cem\u003eR\u003c/em\u003e. \u003cem\u003erickettsii\u003c/em\u003e, so they can transmit the bacteria to their ectoparasites and cause zoonotic transmission to humans or other domestic animals, as has been documented in some parts of the world (Binder et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Beristain-Ruiz et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe present study did not register the ectoparasite species that infested dogs. It is documented that dogs have contact with \u003cem\u003eRickettsia\u003c/em\u003e SFG through the vectorial via generated by several tick species (biological vectors), including \u003cem\u003eRhipicephalus linnaei\u003c/em\u003e (\u003cem\u003e=\u0026thinsp;R\u003c/em\u003e. \u003cem\u003esanguineus sensu lato\u003c/em\u003e) (Peniche-Lara et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015b\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Foley et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Pacheco-Solano et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Beristain-Ruiz et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Salomon et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This tick has an endophilic behavior, wide distribution, and large populations in regions with tropical climates from Mexico, such as the Yucatan Peninsula (Rodr\u0026iacute;guez-Vivas et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; S\u0026aacute;nchez-Montes et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2021b\u003c/span\u003e), so it is frequently found infesting dogs from localities with characteristics similar to this study (Peniche-Lara et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015b\u003c/span\u003e; \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Mart\u0026iacute;nez-Ortiz et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ojeda-Chi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eOther findings that explain \u003cem\u003eRickettsia\u003c/em\u003e SFG vectorial via are those of V\u0026aacute;zquez-Guerrero et al. (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), who evidenced DNA of \u003cem\u003eR\u003c/em\u003e. \u003cem\u003eamblyommatis\u003c/em\u003e and \u003cem\u003eR\u003c/em\u003e. \u003cem\u003ebellii\u003c/em\u003e (members of SFG) in ticks such as \u003cem\u003eAmblyomma auriculatum\u003c/em\u003e, \u003cem\u003eA\u003c/em\u003e. \u003cem\u003eovale\u003c/em\u003e, and \u003cem\u003eA\u003c/em\u003e. \u003cem\u003emixtum\u003c/em\u003e collected in dogs from Yucatan. Finally, Mart\u0026iacute;nez-Ortiz et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) found molecular evidence of \u003cem\u003eRickettsia\u003c/em\u003e sp. in ticks of various genera and species (\u003cem\u003eA\u003c/em\u003e. \u003cem\u003emixtum\u003c/em\u003e, \u003cem\u003eR\u003c/em\u003e. \u003cem\u003esanguineus\u003c/em\u003e s. l., and \u003cem\u003eIxodes affinis\u003c/em\u003e) collected from dogs in a locality of Yucatan whit history rickettsiosis outbreak among its inhabitants. Therefore, the authors suggest that those ectoparasites may have played a role in the zoonotic transmission of the bacteria. The presentation and distribution of diseases transmitted by ticks, such as SFG rickettsiosis, are influenced by complex demographic, ecological, environmental, and social factors, such as the population density of ticks and their hosts, including dogs (Torres-Castro et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2020\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eAccording to the multinomial model, dogs living in dwellings in the central area of Uc\u0026uacute; have a lower risk (RR\u0026thinsp;=\u0026thinsp;0.14, 95% CI 0.02\u0026ndash;0.67) for \u003cem\u003eRickettsia\u003c/em\u003e SFG infection than those living in the other areas. Getting background information to compare our research is challenging due to the lack of previous studies using our sampling design or similar. We collected biological samples and data (variables) for risk infection analysis based on a convenient geographical division of the study site into concentric areas and a specific number of studied dwellings by area. So, this \u0026lsquo;spatial system\u0026rsquo; for studying the infection of \u003cem\u003eRickettsia\u003c/em\u003e resulted in favorable findings of risk areas in mammal hosts from the study site.\u003c/p\u003e \u003cp\u003eDog-free access to the outside of the dwelling was not significant in the corresponding model. However, the protective value of the \u0026ldquo;interior area\u0026rdquo; variable can be partially explained by the behavior of wandering outside the dwelling, which, according to the data collected in the questionnaire (data not shown), was less frequent than in dogs from dwellings in the central and exterior areas, probably because these areas had less density of dwellings (field observation) limiting the owners to keep their dogs inside the premises. Wandering outside the dwelling has been associated with contact with \u003cem\u003eRickettsia\u003c/em\u003e SFG transmission scenarios, such as vacant lots, vegetated areas, unpaved roads, etc., where other dogs and hosts, including synanthropic and wild fauna, and \u003cem\u003eRickettsia\u003c/em\u003e SFG vectors, also circulate (Palacios-Santana et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In this sense, Szab\u0026oacute; et al. (\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) found a positive correlation between seropositivity against \u003cem\u003eRickettsia\u003c/em\u003e SFG in dogs with access to vegetated areas around the dwellings. It is relevant to mention that the dwellings in the exterior area of Uc\u0026uacute; are surrounded by original vegetation (tropical deciduous forest) with areas of seasonal agriculture.\u003c/p\u003e \u003cp\u003eAnother aspect that helps explain the lower risk of \u003cem\u003eRickettsia\u003c/em\u003e SFG infection in dogs from the interior area of the study location is the veterinary care (vaccination and periodic deworming). It was observed that dogs from the interior area of Uc\u0026uacute; received better veterinary care. Also, the lack of ectoparasite control was a frequent characteristic of dogs from dwellings in the central and exterior areas (data not shown). Lack of veterinary care has been associated with higher ectoparasite infestation levels (Ojeda-Chi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), increasing the risk of \u003cem\u003eRickettsia\u003c/em\u003e transmission. Likewise, Forshey et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) point out that dogs that stay in their homes longer tend to receive better health care from their owners, considerably reducing their probability of being parasitized by ticks and the risk of \u003cem\u003eRickettsia\u003c/em\u003e infection.\u003c/p\u003e \u003cp\u003eThe snPCR showed the presence of \u003cem\u003eRickettsia\u003c/em\u003e TG and SFG in the rodents. Detecting \u003cem\u003eRickettsia\u003c/em\u003e in rodents such as \u003cem\u003eM\u003c/em\u003e. \u003cem\u003emusculus\u003c/em\u003e and \u003cem\u003eR\u003c/em\u003e. \u003cem\u003erattus\u003c/em\u003e has been identified as a significant risk factor for the indirect transmission of these bacteria to humans (Forshey et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Rungrojn et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Only one species of \u003cem\u003eRickettsia\u003c/em\u003e TG, \u003cem\u003eR\u003c/em\u003e. \u003cem\u003etyphi\u003c/em\u003e, has been reported in small rodents captured in different localities in the state of Yucatan (Peniche-Lara et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015a\u003c/span\u003e; Torres-Castro et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; S\u0026aacute;nchez-Montes et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e). On the other hand, for \u003cem\u003eRickettsia\u003c/em\u003e SFG, serological positive reactions have been detected in serum samples of rodents from the city of M\u0026eacute;rida (Dzul-Rosado et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIt is recognized that the most important competent vectors of \u003cem\u003eRickettsia\u003c/em\u003e TG in its classic transmission cycle are the fleas of small rodents (\u003cem\u003eXenopsylla cheopis\u003c/em\u003e) (Leulmi et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), so the contact of these animals with these bacteria has been confirmed in numerous studies carried out in endemic areas. For example, in rodents from Spain, Lled\u0026oacute; et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) reported antibodies against \u003cem\u003eR\u003c/em\u003e. \u003cem\u003etyphi\u003c/em\u003e. The same findings were obtained by Mostorino et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) in rodents from the District of Puncha, Peru, where febrile cases compatible with murine typhus (\u003cem\u003eR\u003c/em\u003e. \u003cem\u003etyphi\u003c/em\u003e) were previously identified in the inhabitants. So, the authors pointed out the rodents as the possible amplifying bacteria hosts. In Mexico, S\u0026aacute;nchez-Montes et al. (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2019\u003c/span\u003e)d pez-P\u0026eacute;rez et al. (2022) molecularly identified \u003cem\u003eR\u003c/em\u003e. \u003cem\u003etyphi\u003c/em\u003e in rodents from Hidalgo and Baja California states, respectively.\u003c/p\u003e \u003cp\u003eThe multinomial analysis showed that rodents from dwellings where opossums were captured had a higher risk of \u003cem\u003eRickettsia\u003c/em\u003e TG infection. Although its participation as an amplifying host is not evident, these results represent new insights into the importance of opossums\u0026rsquo; role in the transmission cycle of \u003cem\u003eRickettsia\u003c/em\u003e TG through its ectoparasites (Santoyo-Col\u0026iacute;n et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The opossums captured in Uc\u0026uacute; were not evaluated by snPCR to identify the \u003cem\u003eRickettsia\u003c/em\u003e groups. However, in the study region, there is serological evidence of contact among these animals with this \u003cem\u003eRickettsia\u003c/em\u003e group (Dzul-Rosado et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAs previously mentioned, the main reservoirs of \u003cem\u003eRickettsia\u003c/em\u003e TG are fleas of small rodents. However, evidence indicates that the cat flea \u003cem\u003eCtenocephalides felis\u003c/em\u003e may be the principal vector of an alternative cycle of \u003cem\u003eR\u003c/em\u003e. \u003cem\u003etyphi\u003c/em\u003e in anthropized environments such as Uc\u0026uacute; (Eisen et al. 2012; Maina et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Santoyo-Col\u0026iacute;n et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). This flea has an indirect life cycle that allows it to infest different mammalian hosts, including small rodents (Peniche-Lara et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015a\u003c/span\u003e) and opossums (Bezerra-Santos et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), which explains the positive correlation between the \u003cem\u003eRickettsia\u003c/em\u003e TG infection in the studied rodents with the presence of opossums.\u003c/p\u003e \u003cp\u003eLike \u003cem\u003eRickettsia\u003c/em\u003e TG, rodents acquire infection with \u003cem\u003eRickettsia\u003c/em\u003e SFG through the bite of ectoparasites (vectorial via), mainly ticks. In this regard, it is known rodents are parasitized by several genera and species of hard ticks, including \u003cem\u003eAmblyomma\u003c/em\u003e, \u003cem\u003eIxodes\u003c/em\u003e, and \u003cem\u003eRhipicephalus\u003c/em\u003e (Rodr\u0026iacute;guez-Vivas et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), which are reservoirs for several members of the SFG (L\u0026oacute;pez-P\u0026eacute;rez et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). For this reason, records of rodents with \u003cem\u003eRickettsia\u003c/em\u003e SFG contact are numerous worldwide. For example, Milagres et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and Quintero-V\u0026eacute;lez et al. (2013) found antibodies against \u003cem\u003eRickettsia\u003c/em\u003e SFG in rodents captured in the state of Minas Gerais, Brazil, and in endemic areas of Antioquia, Colombia, respectively. In Mexico, \u003cem\u003eR\u003c/em\u003e. \u003cem\u003erickettsii\u003c/em\u003e (SFG) was identified with molecular tools in biological samples of different species of rodents captured in several regions (Sosa-Guti\u0026eacute;rrez et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe multinomial GLM showed a higher risk (RR\u0026thinsp;=\u0026thinsp;21; 95% CI 2.3\u0026ndash;196) of \u003cem\u003eRickettsia\u003c/em\u003e SFG infection in rodents captured in dwellings where a dog infected by SFG occurs. This finding is relevant because it indicates that rodents and dogs could be involved in the same \u003cem\u003eRickettsia\u003c/em\u003e SFG transmission cycle. However, molecular and bioinformatic analyses of \u003cem\u003eRickettsia\u003c/em\u003e populations are necessary to prove this hypothesis.\u003c/p\u003e \u003cp\u003eThe relationship between rodents and dogs infected with SFG \u003cem\u003eRickettsia\u003c/em\u003e could be linked to several tick species having more than one host through the development cycle. For example, in the \u003cem\u003eAmblyomma\u003c/em\u003e complex, ticks' immature stages infect rodents (Fernandes-Martins et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), and their adult stages infect larger mammals like dogs (Rodr\u0026iacute;guez-Vivas et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In this context, it is known that the maintenance of some members of \u003cem\u003eRickettsia\u003c/em\u003e SFG is due to horizontal transmission. Therefore, all stages (larvae, nymph, and adult) can participate in the \u003cem\u003eRickettsia\u003c/em\u003e SFG transmission among susceptible hosts such as rodents and dogs (Moraes-Filho et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Suwanbongkot et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn a recent study, antibodies against \u003cem\u003eRickettsia\u003c/em\u003e SFG were determined in rodents and dogs from the same dwellings (Dzul-Rosado et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Similarly, what was found in our analyses indicates that these animals are sharing \u003cem\u003eRickettsia\u003c/em\u003e transmission cycles through a possible exchange of vector ectoparasites (Issae et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis study provides new evidence on the participation of dogs and rodents in the epidemiological cycles of \u003cem\u003eRickettsia\u003c/em\u003e groups circulating in the study area. Our findings suggest that these animals are involved in the same transmission cycle through ectoparasite exchange, mainly fleas and ticks. Statistical modeling reveals that the spatial location of the dwelling, the presence of infected dogs, and the presence of opossums in the same dwelling help as proxies of the risk of infection in the synanthropic rodents captured in the premises.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo the families of Uc\u0026uacute;, Yucat\u0026aacute;n, for allowing us into their homes. To the National Council of Science and Technology of Mexico (CONACYT in Spanish) for the scholarship (no. 1089347) granted to one of the authors. To Dr. Rosa Mar\u0026iacute;a Galaz \u0026Aacute;valos for the support for the fieldwork.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatement of Animal Ethics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Bioethics Committee of the Faculty of Veterinary Medicine of the \u003cem\u003eUniversidad Aut\u0026oacute;noma de Yucat\u0026aacute;n\u0026nbsp;\u003c/em\u003e(UADY), Merida, Mexico (minute CB-CCBA-M-2021-003).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe Ministry of Environment and Natural Resources (SEMARNAT in Spanish) of Mexico authorized the capture and extraction of rodents for scientific collection purposes (minute 31/K5-0108/12/20). Additionally, we followed the Guide for the Management of Wild Animals outlined by the American Society of Mammalogists (Sikes et al., 2016). The studied dogs were handled with owner consent and properly signed permits.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eC\u0026eacute;sar Lugo-Caballero and Marco Torres-Castro performed conceptualization. Abigail Arroyo-Ram\u0026iacute;rez, C\u0026eacute;sar Lugo-Caballero, Enrique Reyes-Novelo, and Marco Torres-Castro performed the methodology. Enrique Reyes-Novelo, Jes\u0026uacute;s Alonso Panti-May, R. Iv\u0026aacute;n Rodr\u0026iacute;guez-Vivas, and Marco Torres-Castro performed formal analysis and investigation. Writing - Abigail Arroyo-Ram\u0026iacute;rez, C\u0026eacute;sar Lugo-Caballero, Enrique Reyes-Novelo, and Marco Torres-Castro performed original draft preparation. C\u0026eacute;sar Lugo-Caballero and Marco Torres-Castro performed funding acquisition. Abigail Arroyo-Ram\u0026iacute;rez, Jes\u0026uacute;s Alonso Panti-May, Alejandro Su\u0026aacute;rez-Galaz, Tana Osorio-Primo, Hugo Ruiz-Pi\u0026ntilde;a, and Marco Torres-Castro performed resources. C\u0026eacute;sar Lugo-Caballero and Marco Torres-Castro performed supervision. All authors are reviewing, reading, and approving the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eArroyo-Ram\u0026iacute;rez A, Lugo-Caballero C, Bolio-Gonz\u0026aacute;lez M, Rodr\u0026iacute;guez-Vivas RI, Reyes-Novelo E, Panti-May JA, Torres-Castro MA (2022) El g\u0026eacute;nero \u003cem\u003eRickettsia\u003c/em\u003e y reportes de infecci\u0026oacute;n en perros de Yucat\u0026aacute;n, M\u0026eacute;xico. Bioagrociencias 15:65\u0026ndash;76. https://dx.doi.org/10.56369/BAC.4266\u003c/li\u003e\n\u003cli\u003eArroyo-Ram\u0026iacute;rez A, Lugo-Caballero C, Panti-May JA, Reyes-Novelo E, Rodr\u0026iacute;guez-Vivas RI, Noh-Pech H, Su\u0026aacute;rez-Galaz A, Osorio-Primo T, Puerto FI, Dzul-Rosado K, Torres-Castro M (2023) An unusual identification of \u003cem\u003eRickettsia parkeri\u003c/em\u003e in synanthropic rodents and domiciliated dogs of a rural community from Yucat\u0026aacute;n, Mexico. 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Front Cell Infect Microbiol 12:880813. https://doi.org/10.3389/fcimb.2022.880813\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Epidemiology, vector-borne diseases, rickettsiosis, companion animals, synanthropic animals, animal health","lastPublishedDoi":"10.21203/rs.3.rs-4451515/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4451515/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRickettsioses caused by the spotted fever group (SFG) and typhus group (TG) are endemic in southeastern Mexico. Dogs and rodents can host several species of these bacteria, but little is known about the epidemiological factors that influence the infection risk in these mammals. This study aims to identify the frequency of \u003cem\u003eRickettsia\u003c/em\u003e SFG and TG infection in the studied animals, to determine the spatial distribution of the hosts, and to identify the factors associated with the infection risk. Genomic DNA was obtained from 66 dog blood samples and 36 rodent spleens collected in 48 dwellings from the rural locality of Uc\u0026uacute;, Yucatan, Mexico. \u003cem\u003eRickettsia\u003c/em\u003e SFG or TG infection was determined using a multiplex semi-nested PCR (snPCR). The predictor variables for the infection risk in dogs and rodents were selected using generalized linear models (GLM) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). snPCR revealed \u003cem\u003eRickettsia\u003c/em\u003e DNA in 28.1% (18/64, 95% CI 17.6%-40.8%) of dogs and 27.8% (10/36, 95% CI 14.2%-45.2%) rodents. Only \u003cem\u003eRickettsia\u003c/em\u003e SFG was detected in dogs, while rodents hosted both \u003cem\u003eRickettsia\u003c/em\u003e TG and SFG. According to the corresponding GLM, dogs living in the interior area of Uc\u0026uacute; have a lower risk of infection by \u003cem\u003eRickettsia\u003c/em\u003e SFG (RR\u0026thinsp;=\u0026thinsp;0.14) than those living in the other areas. The presence of opossums (\u003cem\u003eDidelphis\u003c/em\u003e sp.) in the dwelling increases the risk of \u003cem\u003eRickettsia\u003c/em\u003e TG infection in rodents (RR\u0026thinsp;=\u0026thinsp;14), and the presence of SFG-infected dogs in the dwelling increases the risk of \u003cem\u003eRickettsia\u003c/em\u003e SFG infection in rodents (RR\u0026thinsp;=\u0026thinsp;21).\u003c/p\u003e","manuscriptTitle":"Epidemiological factors associated with the spatial distribution of two Rickettsia hosts in a locality of Yucatán, Mexico","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-10 04:22:08","doi":"10.21203/rs.3.rs-4451515/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6eca3f9a-a849-4d8a-b46e-bab205efd73f","owner":[],"postedDate":"June 10th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-06-10T04:22:11+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-10 04:22:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4451515","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4451515","identity":"rs-4451515","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}