Spatial and risk factor analyses of vector-borne pathogens among shelter dogs in the eastern United States

Background: Vector-borne infections pose significant health risks to humans, domestic animals, and wildlife. Domestic dogs ( Canis lupus familiaris ) in the United States may be infected with and serve as sentinel hosts for several zoonotic vector-borne pathogens. In this study, we analyzed the geographic distribution, risk factors, and co-infections associated with infection with Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi , and Dirofilaria immitis in shelter dogs in the eastern United States. Methods From 2016–2020, blood samples from 3,750 shelter dogs from 19 states were examined with IDEXX SNAP® 4Dx® Plus tests to determine prevalence of infection with tick-borne pathogens and infection with D. immitis . We assessed the impact of factors including age, sex, intact status, breed group, and location on infection using logistic regression. Results Regional variation in detection prevalence was noted: D. immitis (17.4%, n = 355/2,036) and Ehrlichia spp. (10.7%, n = 217/2,036) were highest in the Southeast while prevalence for B. burgdorferi (19.3%, n = 143/740) and Anaplasma spp. (5.7%, n = 42/740) were highest in the Northeast. Overall, 4.8% (n = 179/3,750) of dogs had co-infections, the most common of which were D. immitis / Ehrlichia spp. (1.6%, n = 59/3,750), B. burgdorferi/Anaplasma spp. (1.5%, n = 55/3,750), and B. burgdorferi/Ehrlichia spp. (1.2%, n = 46/3,750). Risk factors significantly influenced infection across the evaluated pathogens were location and breed group. All evaluated risk factors were significant for the prevalence of D. immitis antigens. Conclusions Our results demonstrate a regionally variable risk of infection with vector-borne pathogens in shelter dogs throughout the eastern United States, likely due to varying distributions of vectors. However, as many vectors are undergoing range expansions or other changes in distribution associated with climate and landscape change, continued vector-borne pathogen surveillance is important for maintaining reliable risk assessment.