Detection of antibodies reactive with Ehrlichia chaffeensis in the raccoon

Antibodies reactive with Ehrlichia chaffeensis were detected in raccoon (Pr ocyon lotor) serum samples by using an indirect immunofluorescence assay. S amples from 411 raccoons trapped in the southeastern United States from 197 7 to 1999 were tested. Serologically reactive samples with reciprocal titer s of greater than or equal to 16 were detected from 83 raccoons (20%) from 13 of 16 counties in eight states, indicating that raccoons are commonly ex posed to E. chaffeensis. Samples collected as early as 1977 were positive. A polymerase chain reaction assay specific for E. chaffeensis failed to det ect the presence of ehrlichial DNA in serum samples from 20 representative seroreactive raccoons. Because of serologic cross-reactivity among antigens derived from different Ehrlichia spp., additional immunologic, molecular, or culture-based studies will be required to confirm E. chaffeensis infecti ons of raccoons in the southeastern United States.