The clinical aspects of Rift Valley Fever virus in household pets. 3. Pathologic changes in the dog and cat.

A gross and histologic examination was performed on 13 kittens and 14 puppies that died after a subcutaneous inoculation of Rift Valley fever virus. The significant gross lesions were confined to the liver and spleen. Both organs were congested, dark red, and very soft. On the serosal and cut surfaces of the liver, very faint gray to yellow foci with hyperemic edges were present. Petechiae and ecchymoses were observed on the serosal surfaces of the heart, mesenteric lymph glands, and mucosal surfaces of the gastrointestinal tract. Focal nepatic necrosis was the most salient histologic change in the liver. The affected liver cells had swollen, eosinophilic, hyaline, or washed-out cytoplasm and pyknotic or fragmented nuclei. Contrary to observations in other species, there was a conspicuous absence of definite Councilman-like bodies and eosinophilic intranuclear inclusions. Significant histologic changes were also found in the heart and brain. The lesions in the heart included acute and chronic myocarditis and necrosis. The histologic changes in the brain were essentially like those of other viral encephalitides atid included focal gliosis and necrosis. The problems encountered in diagnosing RVF in the canine and feline species are discussed, together with the important epidemiological aspects.