Experimental and Field Studies on the Suitability of Raccoons (Procyon lotor) as Hosts for Tick-Borne Pathogens

We investigated the experimental susceptibility and natural exposure of raccoons ( Procyon lotor ) to five tick-borne pathogens of human and veterinary importance, Ehrlichia canis, E. chaffeensis, E. ewingii, Anaplasma phagocytophilum (ApVariant 1 and Ap-ha HGE-1 strains), and Borrelia lonestari . Infections were assessed by polymerase chain reaction (PCR), indirect fluorescent antibody (IFA) testing, and or culture isolation methods for at least 30 days postinoculation (DPI). Two E. chaffeensis -inoculated raccoons seroconverted and were transiently PCR positive. One raccoon was culture positive. Laboratory raised Amblyomma americanum nymphs fed on a third infected raccoon failed to become infected. Two A. phagocytophilum (HGE-1)-inoculated raccoons became PCR positive and seroconverted. Both remained positive for at least 74 DPI. In contrast, raccoons inoculated with A. phagocytophilum (Ap-Variant 1) were only transiently PCR positive and only seroconverted with low titers. No evidence of infection was observed for E. ewingii - and B. lonestari -inoculated raccoons. Only one E. canis -inoculated raccoon was PCR positive 3 DPI. Serologic testing of wild raccoons from five populations (3 infested with ticks) in Georgia and Florida showed antibodies reactive with E. chaffeensis in the 3 tick-infested populations (range of 30%-46%), E. canis in the same three populations (8%-23%), A. phagocytophilum in a single raccoon from Florida (12%), and Borrelia spp. in all 5 populations (8%-53%). All raccoons were PCR negative for tick-borne pathogens. These data suggest that raccoons are likely not important reservoirs of E. canis, E. ewingii , or B. lonestari . However, raccoons are experimentally susceptible and naturally exposed to E. chaffeensis , and these data support the previous finding that raccoons may be involved in the natural history of A. phagocytophilum .