beagles

A canine model for human monocytic ehrlichiosis was used to assess persistent infection and antigenic variation of Ehrlichia chaffeensis. Two beagle dogs were infected subcutaneously with E. chaffeensisArkansas strain. The dogs were observed for 6 months after inoculation for clinical signs, blood chemistry changes, antibodies to E. chaffeensis and presence of E. chaffeensis in the blood. Both dogs developed thrombocytopenia, but exhibited normal body temperatures during the entire course of infection. In one dog, E. chaffeensiswas cultivated for up to 74 days post-inoculation and E. chaffeensis DNA was detected in the dog’s blood for up to 81 days. In the other dog, E. chaffeensis was cultured for up to 102 days and E. chaffeensis DNA was detected in the blood for up to 117 days. PCR amplification and DNA sequence analysis indicated that there was no genetic variation in the 120 kDa outer-membrane glycoprotein gene of E. chaffeensis during infection of the dogs. The dogs developed antibodies to the immunodominant proteins of E. chaffeensis, includin