Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

loss of hair developed.The clinical signs persisted for several months with temporary improvements of health. During this time the dog was treated many times with antibiotics, glucocorticoides and vitamins. Ultimately, the dog was submitted to the Small Animal Hospital of the University of Veterinary Science, Budapest at 14 months of age. Apathy, convulsions and tetraplegia were noticed. The dog died shortly after its admission to the hospital. Pathology The dog was necropsied. Sections of brain fixed in 10 % buffered neutral formalin were stained with hematoxylin and eosin (HE) and with anti-M caninum and anti-r gondii antibody sera in an avidin-biotin complex immunohistochemical test using the methods of Lindsay and Dubey (1989) and Anderson et al. (1991). Sections of brain were deparaffinized and processed for transmission electron microscopy as described previously (Dubey et al. 1989a). RESULTS Necropsy examination revealed no major gross abnormality. There was no evidence of concomitant infection. Microscopically severe, chronic, non-suppurative, necrotising meningoencephalitis diffusely affected both grey and white matter. Tachyzoites and tissue cysts were dispersed in the lesions. Tachyzoites were seen individually and as large aggregates. Tissue cysts up to 50 //m in diameter contained numerous slender bradyzoites and had 1-2 /urn thick cyst walls. In transmission electron micrographs numerous tachyzoites seen in neural tissue were in division into 2 zoites, indicating the fast replication of the organism. Unfortunately, the organelles were partly disrupted because of autolysis. Tachyzoites and tissue cysts stained positively with both anti-M caninum and anti-Z gondii antibody sera. DISCUSSION Staining of the parasite with both T. gondii and N. caninum antisera is perplexing but N. caninum from naturally infected dogs occasionally reacts with anti-r gondii serum (Dubey et al. 1990b). The clinical history of ascending posterior paralysis is characteristic of neosporosis (Dubey 1990). There was no evidence of concomitant infection, contrary to what is generally seen in toxoplasmosis (Dubey and Beattie 1988). The tissue cyst walls were thicker those that of T. gondii. Large groups of dividing tachyzoites are rare in T. gondii infection. These findings which were similar to those reported in other natural cases of canine neosporosis (Bjerkâs et al. 1984, Dubey et al. 1988a,b, 1990a, Munday et al.