in Sheep
Overview
- Rift Valley fever (RVF) is a peracute or acute, mosquito-borne, zoonotic disease of domestic and wild ruminants in Africa, Madagascar, and the Arabian Peninsula. Large outbreaks of clinical disease are usually associated with heavy rainfall and localized flooding.
- RVF virus belongs to the genus Phlebovirus and is a typical Bunyavirus.
Clinical signs
- Clinical signs of RVF tend to be nonspecific, rendering it difficult to recognize individual cases. The incubation period is 12–36 hr in lambs, and a biphasic fever of up to 108°F (42°C) may develop. Affected animals are listless and reluctant to move or feed and may show signs of abdominal pain. Mortality in young lambs is high (90%–100%), and animals usually die within 2–3 days. Adult sheep are less susceptible, with 10%–30% mortality; the incubation period is 24–72 hr, and animals show a generalized febrile response, lethargy, hematemesis, hematochezia, and nasal discharge, although infection may also be inapparent.
Diagnosis and differentials
- RVF should be suspected when abnormally heavy rains and flooding are followed by widespread occurrence of abortions and mortality among newborn animals characterized by necrotic hepatitis, concurrent with influenza-like disease in people handling animals or their products.