Tick-Borne Disease Agents in Various Wildlife from Mississippi

Abstract

Because tick-borne diseases are becoming increasingly important throughout the world, monitoring their causative agents in wildlife may serve as a useful indicator of potential human exposure. We assessed the presence of known and putative zoonotic, tick-borne agents in four wildlife species in Mississippi. Animals were tested for exposure to or infection with Ehrlichia chaffeensis, Ehrlichia ewingii, Borrelia lonestari, Rickettsia spp., Anaplasma phagocytophilum, and Francisella tularensis. Whole blood and serum were tested from white-tailed deer (WTD; Odocoileus virginianus) and feral swine (Sus scrofa); serum was tested from raccoons (Procyon lotor) and opossums (Didelphis virginiana). We used polymerase chain reaction to detect all agents in blood, whereas an indirect fluorescent antibody assay was used to detect antibodies to E. chaffeensis, B. lonestari, and Rickettsia parkeri (spotted fever group rickettsiae) antigens in serum. Molecular evidence of infection with E. chaffeensis, B. lonestari, and An. phagocytophilum was detected only in WTD. Antibodies to E. chaffeensis antigen were detected in 43.9% of WTD, 32.8% of swine, 42.1% of raccoons, and 15.8% of opossums. Serologic evidence of exposure to B. lonestari antigen was found in 19.3% of WTD, 6.9% of swine, and 5.3% of raccoons, but not in opossums. Interestingly, the percent of animals with antibodies reactive to spotted fever group rickettsiae (R. parkeri antigen) was highest in raccoons (73.7%) and opossums (57.9%). These results support the role of WTD as reservoirs for E. chaffeensis, B. lonestari, and An. phagocytophilum, as well as provide additional evidence for exposure of raccoons and opossums to E. chaffeensis. Finally, we provide new data that feral swine may have antibodies to these agents. Thus, in general, these four wildlife species are exposed to tick-borne disease agents in Mississippi, suggesting that ticks carry and have the potential to transmit the agents to humans in the state.