Attempted experimental infection of domestic goats with Ehrlichia chaffeensis

Although white-tailed deer (WTD; Odocoileus virginianus) are considered the primary natural reservoir host for Ehrlichia chaffeensis, the causative agent of human monocytotropic ehrlichiosis, the potential role of other vertebrates as reservoir hosts has not been fully explored. Because domestic goats are naturally infected in areas where E. chaffeensis is endemic in deer, we evaluated the susceptibility of domestic goats to experimental infection with E. chaffeensis. A total of 12 goats were inoculated with E. chaffeensis (15B-WTD-GA or Ark strain)-infected DH82 cells by one of three routes: intravenously, subcutaneously, or intradermally. White-tailed deer simultaneously inoculated with the same dose, route, and inoculum served as positive controls; additional goats and WTD were included as negative controls. Evidence of E. chaffeensis infection was evaluated in all animals by indirect fluorescent antibody assay, PCR, and cell culture isolation techniques. All goats exposed to E. chaffeensis seroconverted by 14 days post-infection (DPI), and E. chaffeensis was isolated from one goat on 3 DPI; however, molecular or cell culture evidence of active infection was not detected in goats later than 3 DPI. White-tailed deer exhibited serologic and molecular evidence of E. chaffeensis infection throughout both trials, and E. chaffeensis was re-isolated in cell culture from all infected WTD on numerous days post-infection. Our results suggest that despite the occurrence of natural infection in goats, this animal may not be susceptible to experimental infection and thus may not serve as a suitable model of E. chaffeensis reservoir host infection.