Serologic evidence of selected vector-borne pathogens in non-owned dogs in the southeast US

Vector-borne pathogens (VBP) associated with ectoparasitism are of concern for animal health, and there are many gaps in surveillance and reporting data. The purpose of this study was to test for four VBPs in a subset of non-owned dogs from county humane societies in Alabama and Georgia that were admitted to the Auburn University College of Veterinary Medicine Hoerlein Spay/Neuter Program for health exams and routine procedures, including bloodwork and testing with the 4Dx® SNAP® Plus (IDEXX Laboratories, Inc., Westbrook, Maine). Visualized ectoparasites were noted and preserved for identification and analysis. From May-October 2019, residual blood (n = 114) was used for preparing blood smears and DNA extraction and PCR. Out of 114 samples, 35.1% (40/114) were seropositive for one or more VBP: Dirofilaria immitis antigen (20.2%; 23/114) and Ehrlichia spp. antibodies (20.2%; 23/114); six VBD-positive dogs (15%) tested positive for both. No dogs had detectable antibodies to Borrelia burgdorferi or Anaplasma spp. (0%; 0/114). Microfilariae of D. immitis were present in 7 blood smears, all from dogs that were D. immitis antigen positive. Morulae or DNA of Ehrlichia or Anaplasma spp. were not identified in any sample. Fleas were documented in 20.4% (23/113) of dogs, 9.7% (11/113) were infested with ticks, predominantly Amblyomma americanum, and co-infestations were noted in 2.7% (3/113). Our data indicate that there is substantial VBP risk in Alabama and Georgia, and that the reservoir potential of domestic animals, especially non-owned animals, along with potential wildlife reservoirs warrants further investigation.