| Ross River virus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Family: | Togaviridae |
| Genus: | Alphavirus |
| Species: | Ross River virus |
Ross River virus (RRV) is a small encapsulated single-strand RNA alphavirus endemic to Australia, Papua New Guinea and other islands in the South Pacific. It is responsible for a type of mosquito-borne non-lethal but debilitating tropical disease known as Ross River fever, previously termed "epidemic polyarthritis". The virus is suspected to be enzootic in populations of various native Australian mammals, and has been found on occasion in horses.[1]
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Taxonomically Ross River virus belongs to the virus genus Alphavirus, which is part of the family Togaviridae. The alphaviruses are a group of small enveloped single-strand positive-sense RNA viruses. RRV belongs to a subgroup of "Old World" (Eurasian-African-Australasian) alphaviruses, and is considered closely related to Sagiyama virus.[1]
The virions themselves contain their genome in a protein capsid 700 Å in diameter. They are characterised by the presence of two glycoproteins (E1 and E2) embedded as trimeric dimers in a host-derived lipid envelope.[2]
Because RRV is transmitted through mosquito vector it is considered an arbovirus, a non-taxonomic term for viruses borne by arthropod vectors.
In 1928 an outbreak of acute febrile arthritis was recorded in Narrandera and Hay in New South Wales, Australia. In 1943 several outbreaks of arthralgia and arthritis were described in the Northern Territory, Queensland and the Schouten Islands, off the northern coast of Papua New Guinea. The name epidemic polyarthritis was coined for this disease. In 1956 an epidemic occurred in the Murray Valley which was compared to "acute viral polyarthritis" caused by Chikungunya virus. The Australian disease seemed to progress in milder fashion. In 1956 serological testing suggested an unknown new species of alphavirus (group A arbovirus) was the likely culprit.[1]
In 1959, a new alphavirus was identified in mosquito (Ochlerotatus vigilax) samples trapped near Ross River, near Townsville, Queensland, Australia. Further serological testing showed that patients who had suffered "epidemic polyarthritis" in Queensland had antibodies to the virus. The new virus was named Ross River virus, and the disease Ross River fever.[1]
The virus itself was first isolated in 1972 using sucking mice. It was found that RRV isolated from human serum could kill mice. However, the serum containing the virus that was used had come from an Aboriginal boy from Edward River, North Queensland. The child had a fever and a rash but no arthritis making the link between RRV and Ross River fever less than concrete.[1]
However RRV was later isolated in humans following a series of epidemic polyarthritis outbreaks in Fiji, Samoa and the Cook Islands, during 1979. RRV was isolated in an Australian patient suffering from Ross River fever in 1985.[1]
In 2010, the Ross River Virus was found to have made its way to the Aundh area in Pune, India and spread to other parts of the city. A tourist to Australia probably returned infected with the virus. The RRV infection is characterized by very high fever, pain in the joints, loss of appetite and weakness. Hydration by sufficient fluid intake is recommended to ensure that the fever does not rise to very dangerous levels. It is recommended that a doctor be consulted immediately as regular paracetamol gives only temporary reprieve from the fever.
In rural and regional areas of Australia, the continued prevalence of Ross River virus is thought to be supported by natural reservoirs such as large marsupial mammals. Antibodies to Ross River virus have been found in a wide variety of placental and marsupial mammals, and also in a few bird species. It is not presently known what reservoir hosts support Ross River virus in metropolitan areas such as Brisbane.[1]
The Southern Saltmarsh mosquito (Aedes camptorhynchus) which is known to carry the Ross River virus was discovered in New Zealand in 1998, and there is an ongoing eradication program by the New Zealand Ministry of Health, involving spraying the insecticide Bti on infested areas. As of June 2007 there have been no reported cases of Ross River Virus that arose in New Zealand.
The study of RRV has been recently facilitated by a mouse model. Inbred mice infected with RRV develop hind-limb arthritis/arthralgia which is similar to human disease. The disease in mice, similar to humans, is characterized by an inflammatory infiltrate including macrophages which are immunopathogenic and exacerbate disease. Furthermore, recent data indicate that the serum component, C3, directly contributes to disease since mice deficient in the C3 protein do not suffer from severe disease following infection.[3]
Ross River fever is also known as Ross River virus infection or Ross River virus disease.
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