Rift Valley fever virus.

Vet Med Today: Zoonosis Update 883 R Valley fever virus is a mosquito-borne pathogen of livestock and humans that historically has been responsible for widespread and devastating outbreaks of severe disease throughout Africa and, more recently, the Arabian Peninsula. The virus was first isolated and RVF disease was initially characterized following the sudden deaths (over a 4-week period) of approximately 4,700 lambs and ewes on a single farm along the shores of Lake Naivasha in the Great Rift Valley of Kenya in 1931. Since that time, RVF virus has caused numerous economically devastating epizootics that were characterized by sweeping abortion storms and mortality ratios of approximately 100% among neonatal animals and of 10% to 20% among adult ruminant livestock (especially sheep and cattle). Infections in humans are typically associated with selflimiting febrile illnesses. However, in 1% to 2% of affected individuals, RVF infections can progress to more severe disease including fulminant hepatitis, encephalitis, retinitis, blindness, or a hemorrhagic syndrome; among severely affected persons who are hospitalized, the case fatality ratio is approximately 10% to 20%. Rift Valley fever epizootics and epidemics can rapidly overwhelm the capacities of the public health and veterinary medical communities to provide rapid diagnostic testing and adequate medical care for affected humans and other animals, which can number in the tens if not hundreds of thousands. Veterinarians, other health personnel, farmers, and abattoir workers also are at high risk of infection from direct contact with infected animals and patients; indeed, many historical outbreaks of RVF disease in Africa were initially detected because of illnesses among veterinarians and their assistants after they performed necropsies on infected animals. In 2008, several veterinarians, staff, and veterinary students at a South African veterinary college were infected after handling and performing necropsies Rift Valley fever virus