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Bovine Viral Diarrhoea Virus (view source)

Revision as of 07:26, 24 August 2010

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==Transmission and Epidemiology==
 
==Transmission and Epidemiology==
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Houe, 1999 Kirkland et. al, 1991
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In most countries, BVDV is endemic and studies detecting antibody have estimated that between 70 and 100% of herds are either currently infected or have recently been infected with bovine viral diarrhoea virus<sup>23</sup>.
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According to antibody-detection based studies, 70 to100% of herds are currently or have recently been infected with BVDV, reflecting the endemic nature of the virus (reviewed by Houe, 1999).  
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BVDV can be transmitted from infected to susceptible cattle in several ways. Firstly, direct contact with a virus-shedding animal can cause disease. Both acutely and persistently infected animals shed virus, but levels of shedding are much higher in persistently infected cattle and transmission is more efficient. Transmission to heifers and cows may also occur venereally or via artificial insemination as acutely and persistently unfected bulls sheed bovine viral diarrhoea virus in their semen<sup>24</sup>. The testes is an immunoprivileged site, and the virus can persist in this location despite otherwise systemic clearance<sup>25</sup>.  
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BVDV can be transmitted from infected to susceptible cattle in several ways. Direct contact with a PI animal is the most efficient method, although interaction with those acutely infected can also give infection. BVDV is also excreted in the semen of both PI and acutely infected bulls, often causing seroconversion of female cattle after insemination (Kirkland et. al, 1991). Bulls and semen should therefore be tested before use for artificial insemination.
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Virus may also be spread indirectly. Use of live or infected vaccines and reuse of needles, nose tongs (Gunn, 1993) or rectal gloves (Lang-Ree et al., 1994) may cause transmission. Blood feeding flies may also spread BVDV (Tarry et. al, 1991).
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Virus may also be spread indirectly. Use of live or infected vaccines and reuse of needles, nose tongs (Gunn, 1993) or rectal gloves (Lang-Ree et al., 1994) may cause transmission. Blood feeding flies may also spread BVDV (Tarry et. al, 1991).
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BVDV is diagnosed by the detection of virus or antibody in blood and milk samples. Antibody detection shows exposure of the herd to disease, whereas tests for antigen identify PI animals which may be antibody negative (Brownlie et. al, 2000).
      
===Epidemiology===
 
===Epidemiology===
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