A Cross-Sectional Study of Small Mammals for Tickborne Pathogen Infection in Northern Mongolia
Introduction: Extensive studies on tickborne pathogens (TBPs) have been conducted in developed nations, relatively less has been done in developing nations leaving a large gap of knowledge. Mongolia, a country built upon nomadic culture and pastoralism is an ideal system to study TBPs as the population is at an increased risk due to increased time spent outside herding livestock. Discoveries of TBPs in Mongolia include Babesia spp., Anaplasma spp., Borrelia spp., Rickettsia spp. and tick-borne encephalitis virus. While research has focused on TBPs in humans and ticks in Mongolia, little research has assessed animal reservoirs, specifically small mammal species, as reservoirs for TBPs. This project aimed to 1) identify the role of small mammal species in the ecology of TBPs in Mongolia, specifically Rickettsia spp., Anaplasma spp., and Borrelia spp. using serological and molecular analysis and 2) identify risk factors associated with the prevalence of TBPs in small mammal populations in Mongolia.
Methods: From June to July 2016, rodents were live-trapped, and whole blood, serum and ear biopsy samples were collected. Sixty-four rodents were trapped in three aimags (provinces) in northern Mongolia. Whole blood samples were tested by PCR to detect the presence of Rickettsia spp., Anaplasma spp., and Borrelia spp.. In addition, ear biopsy samples were tested by PCR to detect the presence of Borrelia spp.. All rodents were serologically tested for antibodies to Anaplasma phagocytophilum and Rickettsia rickettsii. A multivariate model was used to assess risk factors for the presence of tickborne pathogens. Risk factors examined included species and sex of animal, location and presence of ticks.
Results: 56.0%, 39.0% and 0.0% of animals were positive by PCR for Borrelia spp., Rickettsia spp. and Anaplasma spp., respectively. 41.9% and 24.2% of animals were seropositive for A. phagocytophilum and Rickettsia rickettsii, respectively. Risk factors found to be important predictors of Borrelia spp. molecular detection included small mammal capture in Tov aimag (OR, 4.1; 95% CI, 1.00 – 16.80), male small mammals (OR, 3.07; 95% CI, 0.99 – 9.51) and ground squirrel species type (OR, 3.24; 95% CI, 0.90 – 11.70). The risk factor found to be an important predictor of Rickettsia spp. molecular detection was Mongolian gerbil species type (OR, 246.5; 95% CI, 20.77 – 2925.88). Presence of ticks on small mammals (OR, 4.62; 95% CI, 0.92 – 23.24) was an important risk factor for A. phagocytophilum antibody detection. No risk factors were identified as being important predictors of antibody detection of R. Rickettsii.
Conclusion: The results of this study provide considerable evidence of TBPs circulating in small mammal populations in Northern Mongolia. Further information on TBPs in ticks, humans, livestock and wildlife reservoirs will be important to address public health interventions for TBPs in Mongolia in the future.
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