Ocular histopathology of ehrlichial infections in the dog

Histologic examination of eyes and brains of 27 dogs experimentally infecte d with either Ehrlichia canis, E, ewingii, E, chaffeensis, or human granulo cytic ehrlichia (HGE) was conducted in the course of several experiments, t he primary objectives of which were to investigate the susceptibility of th e domestic dog to infection with various ehrlichial species and to assess t he ability of ixodid tick species to acquire and transmit those infections. Uveitis and meningitis occurred in each of the dogs infected with E. canis but was not observed in dogs infected with the other Ehrlichia species. Th e inflammatory infiltrate was predominantly lymphocytic, monocytic, and pla smacytic; granulocytes were notably few. Ocular inflammation was most commo n and most intense in the ciliary body, becoming less intense in the choroi d, iris, and retina, respectively. Meningitis was often accompanied by mild neuroparenchymal vascular cuffing and gliosis. The meningeal inflammatory cell infiltrate included a prominent monocyte population. Ocular and mening eal lesions were present in all E. canis-infected dogs from 22 through 200 days postexposure. Neither ocular nor brain lesions were observed with any of the other ehrlichial infections.