Shelter dogs harbor diverse tick species and demonstrate high exposure to tick-borne pathogens in a zone of tick range expansion

Objective: To characterize ticks and tick-borne pathogens (TBPs) among Ohio shelter dogs and identify factors associated with canine exposure. Methods: This cross-sectional study included dogs admitted to an Ohio shelter partner between January 2020 and January 2021. Paired tick and blood samples were collected at intake. Ticks were identified and tested for TBPs by PCR; dogs underwent serologic testing and PCR. Logistic regression assessed associations between demographic and clinical variables and seropositivity. Results: A total of 273 dogs were enrolled. Four tick species, including Haemaphysalis longicornis, were found on 22% of dogs. Overall, 43.9% were seropositive for ≥ 1 TBP and 24% for multiple TBPs. Seroprevalence was highest for Borrelia burgdorferi (33.5%) followed by Ehrlichia spp (24.4%) and Rickettsia spp (19.8%). Few dogs were PCR positive, and clinical signs were uncommon (3.7%). Tick PCR detected several relevant pathogens. Tick presence and host factors were associated with increased odds of seropositivity. Conclusions: Ohio shelter dogs demonstrate high exposure to diverse TBPs despite few PCR-positive results and infrequent clinical signs. Paired testing of dogs and attached ticks provides integrated information relevant to veterinary and public health surveillance in a region experiencing increasing tick abundance and pathogen prevalence. Clinical Relevance: Tick presence at intake may help prioritize testing when universal screening is infeasible. Rickettsia seropositivity should be interpreted cautiously because serologic cross-reactivity complicates clinical interpretation and species-level attribution.