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''Wesselsbron'' (WSL) ''virus'' is an
Since the flock had been vaccinated 2 weeks before for protection against the Rift Valley virus, the possibility of a "new" disease was not put into consideration; the vaccine was assumed to be the culprit. Although they both share similarities, the WSL virus was isolated as distinct from the Rift Valley virus after the examination of a dead lamb's liver and brain.
arthropod-borne virus
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more spe ...
in the genus ''Flavivirus
''Flavivirus'' is a genus of positive-strand RNA viruses in the family ''Flaviviridae''. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may caus ...
'' of the family ''Flaviviridae
''Flaviviridae'' is a family of enveloped positive-strand RNA viruses which mainly infect mammals and birds. They are primarily spread through arthropod vectors (mainly ticks and mosquitoes). The family gets its name from the yellow fever virus ...
'' that causes Wesselsbron disease
''Wesselsbron'' (WSL) ''virus'' is an arthropod-borne virus in the genus '' Flavivirus'' of the family ''Flaviviridae'' that causes Wesselsbron disease in cattle, sheep, goats, camels, pigs, donkeys, horses, ostriches, and wild ruminants with ...
in cattle, sheep, goats, camels, pigs, donkeys, horses, ostriches, and wild ruminants with occasional incidental spillover to humans. It is transmitted by mosquitoes in the genus ''Aedes
''Aedes'' is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except perhaps Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', a particularly invasive spe ...
'' including ''A. caballus'' and ''A. circumluteolus''.
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History
The first known outbreak was reported in 1955 on a sheep farm in the town ofWesselsbron
Wesselsbron is a small maize farming town 75 kilometres south of Bothaville in Free State province of South Africa.
Town 32 km east of Hoopstad and 48 km north-west of Welkom. It was laid out in 1920 and became a municipality in 1936. ...
s in Orange Free State Province
The Province of the Orange Free State ( af, Provinsie Oranje-Vrystaat), commonly referred to as the Orange Free State ( af, Oranje-Vrystaat), Free State ( af, Vrystaat) or by its abbreviation OFS, was one of the four provinces of South Africa from ...
, South Africa after an increase of lamb deaths and ewe abortions. Since the flock had been vaccinated 2 weeks before for protection against the Rift Valley virus, the possibility of a "new" disease was not put into consideration; the vaccine was assumed to be the culprit. Although they both share similarities, the WSL virus was isolated as distinct from the Rift Valley virus after the examination of a dead lamb's liver and brain.
Geographical Distribution
Since 1955, WSL virus has been found in animals and mosquitos from Zimbabwe, Uganda, Kenya, Nigeria, Central African Republic, Senegal, Cameroon, and Ivory Coast.Serologic
Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mic ...
evidence has also shown the virus to be present in Mozambique, Botswana, Namibia, Angola, and Madagascar. Outside of Africa, WSL virus has been found in Thailand.
Effect on Sheep
Although it can infect a wide variety of animals, WSL virus is most commonly found in sheep. In newborn lambs, death may occur within 72 hours following an incubation period of 1–3 days. Signs of illness, which include but are not limited to fever, anorexia, listlessness, weakness, and increased respiration, can often go undetected because they are not specific to any disease. Pregnant ewes generally suffer from abortions, but rams and non-pregnant ewes usually only develop a fever. There is no specific treatment for the virus, but sheep can be immunized with an attenuated vaccine that lasts a lifetime.Human Cases
Most documented human infections have been acquired by field workers bitten by mosquitoes or in the laboratory. Person-to-Person transmission of the virus has yet to be reported, so it is not considered to be contagious in humans. The WSL virus has an incubation period of 2–4 days before leading to a sudden onset of a generally mild, acute phase that includes fever, rigors, headache, myalgia, arthralgia, and impaired vision.References
External links
* {{Taxonbar, from=Q18968274 Bovine diseases Flaviviruses Sheep and goat diseases