ISOLATION OF EHRLICHIA-CHAFFEENSIS FROM WILD WHITE-TAILED DEER (ODOCOILEUS-VIRGINIANUS) CONFIRMS THEIR ROLE AS NATURAL RESERVOIR HOSTS

Field and experimental studies have implicated white-tailed deer (Odoc oileus virginianus) as probable reservoir hosts for Ehrlichia chaffeen sis, the causative agent of human monocytic ehrlichiosis, but natural infection in deer has not been confirmed through isolation of E. chaff eensis. Thirty-five white-tailed deer collected from three Amblyomma a mericanum-infested populations in Georgia were examined for evidence o f E. chaffeensis infection by serologic, molecular, cell culture, and xenodiagnostic methods. Twenty-seven deer (77%) had E. chaffeensis-rea ctive indirect fluorescent-antibody assay titers of greater than or eq ual to 1:64; and the blood, spleens, or lymph nodes of seven (20%) dee r were positive in a nested PCR assay with E. chaffeensis-specific pri mers. E. chaffeensis was isolated in DH82 cell cultures from the blood of five (14%) deer, including two deer that were PCR negative. Combin ation of culture and PCR results indicated that six (17%) deer were pr obably rickett-semic and that nine (26%) were probably infected. Restr iction digestion of PCR products amplified from deer tissues anti cell culture isolates resulted in a banding pattern consistent with the E. chaffeensis 16S rRNA gene sequence. The sequences of all PCR products from deer tissues or cell culture isolates were identical to the sequ ence cf the Arkansas type strain of E. chaffeensis. Xenodiagnosis with C3H mice inoculated intraperitoneally with deer blood, spleen, or lym ph node suspensions was unsuccessful. When viewed in the context of pr evious studies, these findings provide strong evidence that E. chaffee nsis is maintained in nature primarily by a tick vector-vertebrate res ervoir system consisting of lone star ticks and white-tailed deer.