Rift Valley fever

An acute, fever-causing viral disease that affects domestic animals (such as cattle, buffalo, sheep, goats, and camels) and humans that is most commonly associated with mosquito-borne epidemics during years of heavy rainfall. Rift Valley fever is caused by the RVF virus. It is found mainly in regions of eastern and southern Africa where sheep and cattle are raised. RVF primarily affects livestock and can cause disease in a large number of domestic animals (a situation referred to as an "epizootic"). An RVF epizootic can lead to an epidemic among people exposed to animals with RFV. The most notable epizootic of RVF to date occurred in Kenya in 1950-1951 and resulted in the death of an estimated 100,000 sheep. The first epidemic of RVF in West Africa was reported in 1987. Epizootics of RVF tend to occur during years in which there is heavy rainfall and localized flooding. The excessive rain allows mosquito eggs, usually of the genus Aedes, to hatch. The mosquito eggs are infected with the RVF virus, and the resulting mosquitoes transfer the virus to the livestock on which they feed. Once the livestock are infected, other species of mosquitoes can become infected from the animals and spread the disease. People get RVF from the bites of mosquitoes. (In addition, it is possible that the virus can be transmitted by other biting insects.) People can also get the RVF by exposure to the blood or other body fluids of infected animals. This exposure may be in slaughtering or handling of infected animals or by touching contaminated meat during the preparation of food. Infection through aerosol transmission of RVF virus has resulted from contact with laboratory specimens containing the virus. Most people with RVF have no symptoms or only a mild illness associated with fever and liver abnormalities. People with more serious symptoms usually experience fever, weakness, back pain, dizziness, and extreme weight loss at the onset of the illness. Typically, they recover within two days to one week after the onset of illness. But RFV can progress to hemorrhagic fever (bleeding which can lead to shock), encephalitis (inflammation of the brain which can cause headaches, seizures, or coma), and eye disease. About 1% of people infected with RVF die of the disease. A common long-term complication of RVF involves the eye. It is due to inflammation of the retina (at the back of the eye), About 1-10% of affected patients suffer some permanent loss of vision. There is no established treatment for RVF. Ribavirin, an antiviral drug, has shown promise in animal trials. Interferon, immune modulators, and convalescent-phase plasma may possibly help in the treatment of RVF.

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Rift Val·ley fever 'rift-.val-ē- n an acute usu. epizootic mosquito-borne disease of domestic animals (as sheep and cattle) chiefly of eastern and southern Africa that is caused by a bunyavirus of the genus Phlebovirus (species Rift Valley fever virus), is marked esp. by fever, abortion, death of newborns, diarrhea, and jaundice, and is sometimes transmitted to humans usu. in a milder form marked by flulike symptoms

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an acute febrile infection of sheep and cattle, zoonotic in humans, caused by a bunyavirus; it spreads to humans by the bites of mosquitoes of the genera Aedes, Culex, and Anopheles or by contact with tissues and secretions of infected animals. In humans it may be in a mild form with nonspecific influenzalike symptoms, or in a severe form with encephalitis, retinitis, or hemorrhagic fever. In other animals it is characterized by fever, listlessness, hepatitis, melena, bloodstained nasal discharge, and abortion in pregnant animals. First observed in the Rift Valley of Kenya, it is now seen throughout southern and eastern Africa as far north as Egypt.