Prevalence, Distribution, and Factors Associated with Vector-Borne Pathogen Infections in Pet Dogs from Different Geoclimatic Zones in Sri Lanka

Vector-borne pathogens (VBPs) cause significant diseases in dogs in the tropics. In Sri Lanka, the scarce availability of previous studies on canine VBPs has hampered an accurate evaluation of their prevalence in pet dog populations. In this study, we collected demographic, clinical, and environmental data together with whole blood from 423 pet dogs from three geoclimatic zones in Sri Lanka. All blood samples were screened using a previously validated multiplex qPCR assay to detect the six most prevalent canine VBPs in tropical Asia. Multivariable logistic regression models were used to investigate environmental and host factors as predictors of VBP infections. Overall, 254 dogs (60.1%, 95% CI: 55.3-64.6%) were infected with one or more VBPs. Babesia gibsoni was the most prevalent VBP with 37.4% (95% CI: 32.7-42.2%) of dogs infected followed by Hepatozoon canis (21.04%, 95% CI: 17.25-25.24%), haemotropic mycoplasmas (10.2%, 95% CI: 7.5-13.4%), Babesia vogeli (5%, 95% CI: 3.2-7.5%), Ehrlichia canis (4.5%, 95% CI: 2.7-6.9%), and Anaplasma platys (3.8%, 95% CI: 2.12-6.1%). Predictors of VBP infections included tick infestation for H. canis (p=0.05) and A. platys (p=0.01), as well as age for B. gibsoni (p=0.01) and H. canis (p=0.05) infection. Local breed (p=0.004), male dogs (p=0.001) and flea infestation (p=0.04) were significantly associated with haemotropic mycoplasma infections suggesting direct-blood exchange through fighting and fleas as a possible means of transmission for these pathogens. Clinical results suggest that B. gibsoni and E. canis caused clinically significant disease, especially in exotic breeds such as German shepherds and Rottweilers compared to the local breeds (p<0.001). Measures such as educating pet dog owners on the importance of being vigilant on ectoparasite infestation of their pets, preventing pet dogs from interacting with stray or community dogs, and the compliant use of effective ectoparasiticides will be crucial for effective control of VBPs in pet dogs in Sri Lanka.