Prevalence of Dirofilaria immitis, Ehrlichia canis, and Borrelia burgdorferi in pet dogs, racing greyhounds, and shelter dogs in Florida

Arthropod vectors of canine infectious diseases are present throughout Florida. Since crowded housing has the potential to bring vectors and infected dogs into close proximity, it is possible that prevalence of infection is higher in intensely housed dogs. In this study, the seroprevalence of Dirofilaria immitis, Ehrlichia canis, and Borrelia burgdorferi in dogs residing in two types of intensive housing, greyhound kennels and animal shelters, was compared to dogs residing in low-intensity housing, private homes. Serum was collected from a cross-section of 1500 adult dogs from Florida, including 500 pet dogs referred to the Veterinary Medical Center of the College of Veterinary Medicine at the University of Florida, 500 racing greyhounds, and 500 dogs residing in animal shelters. Serum was tested for D. immitis antigen, E. canis antibodies, and B. burgdorferi antibodies by ELISA. Seroprevalence of D. immitis was significantly higher (14.6%) in shelter dogs and in pet dogs (1.4%) than in racing greyhounds (0.2%) (P < 0.04). There were no significant differences in the seroprevalence of E. canis (0.4–1.6%) or B. burgdorferi (0–0.8%) among the groups. There was no association of sex or age with D. immitis infection, but pit bull type dogs were more than twice as likely to be infected than other breeds (P = 0.003). Evidence for vector-borne infections, particularly D. immitis, was found in dogs throughout the state. The prevalence was greatest for D. immitis infection in shelter dogs, likely due to lack of preventive medications prior to impoundment. Although heartworm infection is considered to be a treatable condition, insufficient resources in shelters may lead to euthanasia of infected dogs that would otherwise be considered adoptable.