Detection of granulocytic Ehrlichia species DNA by PCR in persistently infected dogs

Three female beagle dogs inoculated with granulocytic Ehrlichia species wer e monitored for four to six months to determine whether there was evidence that the organisms persisted. The dogs were inoculated intravenously with b lood containing an Ehrlichia species closely related to Ehrlichia equi and Ehrlichia phagocytophila. and identical to the human granulocytic ehrlichio sis agent with respect to its 16S rRNA gene sequence. The clinical signs we re evaluated, and blood samples were collected for haematology, serum bioch emistry and serology. Ehrlichial inclusions in the blood were monitored by microscopy, and ehrlichial DNA was detected by the polymerase chain reactio n (PCR). Two of the dogs were injected with prednisolone on days 54 to 56 a nd days 152 to 154 after infection, and the other was injected with prednis olone on days 95 to 97 after infection. The dogs were euthanased and examin ed postmortem. Ehrlichial inclusions were demonstrated in the neutrophils a nd seroconversion occurred shortly after inoculation. Two of the dogs devel oped acute disease with rectal temperatures above 39.0 degrees C, after whi ch no further clinical signs were observed. The administration of corticost eroids seemed to facilitate the detection of ehrlichial inclusions. Ehrlich ial DNA was detected intermittently by PCR in blood samples from two of the dogs throughout the study. Persistent infection was demonstrated up to fiv e-and-a-half months after inoculation.