Epidemiology of Vector-Borne Pathogens Among U.S. Government Working Dogs

Abstract

Surveillance of U.S. domestic dogs for exposure to vector-borne pathogens can identify regions of transmission that are relevant for human and animal health. Working dogs with high levels of outdoor exposure may be sensitive indicators of local risk, owing to increased contact with vectors. We randomly selected 476 high-value government working dogs from 40 states to determine the prevalence of infection with <i>Dirofilaria immitis</i> and <i>Rickettsia</i> spp., and exposure to <i>Ehrlichia</i> spp., <i>Anaplasma</i> spp., and <i>Borrelia burgdorferi</i>, and identify risk factors for positivity. Additionally, we tested 100 of these dogs from Texas for <i>Leishmania</i> spp. where sand fly vectors occur. Previously published <i>Trypanosoma cruzi</i> infection data on these dogs were used to identify coinfection or co-exposures. Infection prevalence was 0.84% for <i>D. immitis</i>, and all dogs were negative for <i>Rickettsia</i> spp. DNA. Seroprevalence of each pathogen was: <i>B. burgdorferi</i> 0.84%, <i>Ehrlichia</i> spp. 1.3%, <i>Anaplasma</i> spp. 1.5%, <i>Leishmania</i> spp. 2.0%, and <i>T. cruzi</i> 12.2%. Coinfection or co-exposure took place in four (0.84%) dogs. In bivariable analysis, we found that <i>D. immitis</i>-positive and <i>Ehrlichia</i>-seropositive dogs were significantly older than negative dogs (<i>p</i> < 0.05). Furthermore, seroprevalence of <i>Anaplasma</i> spp. was significantly higher among dogs in the Northeast United States relative to other areas of the country (4.7% vs. ≤1.4%; <i>p</i> = 0.041). Although autochthonous <i>Leishmania</i> infections have been described in the United States, the cases reported herein may represent imported <i>Leishmania</i> infection. Most federal working dogs are bred in Europe, where the parasite is endemic and congenitally transmitted. Serological cross-reaction between <i>T. cruzi</i> and <i>Leishmania</i> spp. complicates diagnosis. In this study, the use of multiple testing strategies in a comparative complementary manner provided evidence for these dogs' true exposures. Comprehensive surveillance for vector-borne pathogens in dogs can improve clinician awareness and target prevention and treatment in a One Health manner.