TEMPORAL ASSOCIATION OF AMBLYOMMA-AMERICANUM WITH THE PRESENCE OF EHRLICHIA-CHAFFEENSIS REACTIVE ANTIBODIES IN WHITE-TAILED DEER

From 1981 through 1993, tick infestations and serum antibodies reactiv e to Ehrlichia chaffeensis, the causative agent of human ehrlichiosis, were monitored among white-tailed deer (Odocoileus virginianus) at Wh itehall Experimental Forest, Clarke County, Georgia (USA). Neither tic ks nor E. chaffeensis antibodies were detected during the first two ye ars of the study. Infestations of the lone star tick (Amblyomma americ anum), a suspected vector of E. chaffeensis, first were noted on deer in 1983. Prevalence and intensity of A. americanum sharply increased f rom 1985 to 1989, and prevalence was 100% from 1990 to 1993. Antibodie s reactive to E. chaffeensis were first detected in 7% of deer sampled in 1986. Antibody prevalence increased to 21% in 1987 and was 100% fr om 1988 to 1993. This temporal association between the establishment o f A. americanum and the appearance of E. chaffeensis antibodies provid es evidence to support the concept that A. americanum could be a natur al vector of E. chaffeensis. The high prevalence of antibodies among a ll age classes of deer also reaffirms that white-tailed deer may be se nsitive natural sentinels for monitoring the distribution of E. chaffe ensis.