Bovine Immunodeficiency Virus
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Description
Bovine Imunodeficiency Virus (BIV) is a Lentivirus (non-oncogenic), a genus of the Retroviridae family. BIV causes a persistent viral infection in cattle, and has been reported in the US, Canada,Europe, Pakistan, Korea, Japan, New Zealand, Australia and several other countries. The virus is morphologically, antigenetically and genetically related to HIV. It was first isolated in 1969 from a cow with a wasting syndrome.
Pathogenesis
BIV has a broad cell tropism and causes a mild lymphoproliferative disorder with low viral titres and no reproducible disease sequelae. As a lentivirus it is able to integrate into the host genome and replicate within macrophages. It is associated with a long incubation period. The mechanism of transfer is not well known,but the following possibilities are being researched :
- Transplacental
- Transmammary
- Vertical transfer through infected semen (e.g. artificial insemination)
Clinical Signs
The virus was originally isolated in 1969 from an 8 year old Holstein cow in the US with lymphocytosis and lymphadenopathy. Bovine immunodeficiency Virus has been associated with the following signs:
- Decreased milk yield
- Clinical immunodeficiency
- Encephalitis
- Bovine paraplegic syndrome
- Skin infections
- Emaciation
Immunocompromised cattle, arising from BIV infection, can develop secondary diseases associated with stress (e.g. parturition or environmental conditions) or systemic disease. It may also be responsible for a poor antibody response to viral vaccines in calves.
Diagnosis
There are difficulties in the isolation of BIV from clinical cases. Serological tests such as immunoflorescence and western blot have been used to identify the virus although virus isolation from these cases has been unsuccessful. Diagnosis by PCR remains the most sensitive test at present.
Treatment and Control
The Incidence of Bovine immunodeficiency virus appears to be low (1%) although can reach >15 % in some herds. Due to the unknown prevalence of the virus in most herds, prevention and control methods are not widely practiced. Treatment is symptomatic.
References
- Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
- Quinn, P.J., Markey, B.K., Carter, M.E., Donnelly, W.J., Leonard, F.C. (2007) Veterinary Microbiology and Microbial Disease Blackwell Publishing
- Marie-Claude St-Louis, Mihaela Cojocariu and Denis Archambault (2004). The molecular biology of bovine immunodeficiency virus: a comparison with other lentiviruses. Animal Health Research Reviews 5, pp 125-143
- Walder R, Kalvatchev Z, Tobin GJ, Barrios MN, Garzaro DJ, Gonda MA. (1995). Possible role of bovine immunodeficiency virus in bovine paraplegic syndrome: evidence from immunochemical, virological and seroprevalence studies.Research in Virology 146(5) pp 313-23.