The Pathogenesis of Rift Valley Fever

Rift Valley fever (RVF), a mosquito-borne zoonotic disease among humans and ruminants, is caused by Rift Valley fever virus (RVFV) belonging to the family Bunyaviridae, genus Phlebovirus. RVF is endemic to sub-Saharan African countries and has caused major outbreaks in several countries including Kenya, Tanzania, Somalia, South Africa, Madagascar, Egypt, Sudan, Mauritania, Senegal, Saudi Arabia, and Yemen. Pregnant ruminants infected with RVFV typically are subject to high- rate abortions, fetal malformation, and subclinical-to-fatal febrile illness, while newborn lambs usually die by acute hepatitis. RVFV infection in humans primarily causes a self-limiting febrile illness; however, some patients develop hemorrhagic fever, neurological disorders, or blindness after the febrile period. In endemic area, floodwater Aedes mosquitoes serve as vectors, and the virus could be transmitted into offspring transovarially. Heavy rainfall or flooding of river banks due to construction of dams increases the number of permanent fresh water species of mosquitoes such as Culex pipens, which play a role in amplifying RVFV among mosquitoes, ruminants and humans. An outbreak of RVF in developed countries, e.g., the U.S. or Europe, could force a curtailing of livestock movement to prevent RVFV spread, causing massive economic loss, and a substantial degree of panic in our society, because the body fluids of infected animals contain infectious RVFV, and mosquitoes such as Culex spp. Aedes spp. or Anopheles spp. might further spread RVFV into other mosquitoes, humans and animals. Effective vaccines and antiviral drugs are necessary for the containment of outbreaks and treatment of RVF patients, respectively. However, neither safe and effective vaccines nor efficient treatment is available. A correct understanding of RVF pathogenesis is essential for the development of effective vaccines and antiviral drugs against RVF. This review describes clinical and pathological findings of RVF in humans and animals and discuss viral and host factors that affect RVF pathogenesis.

Rift Valley Fever

The Pathogenesis of Rift Valley Fever. Viruses 2011, 3(5), 493-519; doi:10.3390/v3050493
Rift Valley fever (RVF) is an emerging zoonotic disease distributed in sub-Saharan African countries and the Arabian Peninsula. The disease is caused by the Rift Valley fever virus (RVFV) of the family Bunyaviridae and the genus Phlebovirus. The virus is transmitted by mosquitoes, and virus replication in domestic ruminant results in high rates of mortality and abortion. RVFV infection in humans usually causes a self-limiting, acute and febrile illness; however, a small number of cases progress to neurological disorders, partial or complete blindness, hemorrhagic fever, or thrombosis. This review describes the pathology of RVF in human patients and several animal models, and summarizes the role of viral virulence factors and host factors that affect RVFV pathogenesis.

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