Changes

===Laboratory Tests===

===Laboratory Tests===

There are several techniques available for the laboratory diagnosis of BVD. These can detect antibody to BVDV, or parts of the virus itself.

There are several techniques available for the laboratory diagnosis of BVD. These can detect antibody to BVDV or parts of the virus itself.

Tests that detect anti-BVDV antibody include the serum neutralisation test, and an ELISA³⁴. The serum neutralisation test depends on the ability of antibodies in the serum to neutralise BVD virus and thereby prevent infection of cell culture. The test takes four to seven days to obtain a result and requires cell culture facilities and an experienced observer. The ELISA detects anti-BVDV antibody when it binds to a specifica viral antigen. The test is completed within one day and is simple to perform. Because antibody against BVDV is prevalent in most cattle populations, a single serologic test is not usually sufficient for diagnosis. Therefore, an increase in antibody titre between paired serum samples must be more than four-fold to confirm recent infection³⁹.

Tests that detect anti-BVDV antibody include the serum neutralisation test, and an ELISA³⁴. The serum neutralisation test depends on the ability of antibodies in the serum to neutralise BVD virus and thereby prevent infection of cell culture. The test takes four to seven days and requires cell culture facilities and an experienced observer. The ELISA detects anti-BVDV antibody when it binds to a specific viral antigen. The test is completed within one day and is simple to perform. Because antibody against BVDV is prevalent in most cattle populations, a single serologic test is not usually sufficient for diagnosis. Therefore, an increase in antibody titre between paired serum samples must be more than four-fold to confirm recent infection³⁹.

Viral antigen or RNA can be detected using clinical specimens or tissue samples. Bovine viral diarrhoea virus can be isolated from blood, nasal swabs or tissues to confirm active infection, and demonstration of virus in samples obtained at least three weeks apart is suggestive of persistent infection. The best tissues for virus isolation are spleen, lymph node and segments of the gastrointestinal tract showing ulcerative lesions. An antigen-cpature ELISA is also available to detect the presence of BVDV antigen in blood or serum, and immunohistochemistry will demonstrate the presence of antigen in fixed or frozen sections. Viral RNA may also be detected, using PCR for clinical specimens and PCR of ''in situ'' hybridisation on fresh or firxed tissues³⁹.  

Viral antigen or RNA can be detected using clinical specimens or tissue samples. Bovine viral diarrhoea virus can be isolated from blood, nasal swabs or tissues to confirm active infection, and demonstration of virus in samples obtained at least three weeks apart is suggestive of persistent infection. The best tissues for virus isolation are spleen, lymph node and segments of the gastrointestinal tract showing ulcerative lesions. An antigen-cpature ELISA is also available to detect the presence of BVDV antigen in blood or serum, and immunohistochemistry will demonstrate the presence of antigen in fixed or frozen sections. Viral RNA may also be detected, using PCR for clinical specimens and PCR or ''in situ'' hybridisation on fresh or fixed tissues³⁹.  

Genotype is generally determined by PCD or nucleic acid sequencing.

Genotype is generally determined by PCR or nucleic acid sequencing.

[[Image:BVD-MD.gif|right|thumb|150px|Small erosions of MDV/BVDV - vesicles are microscopic (Courtesy of Alun Williams, RVC)]]

[[Image:BVD-MD.gif|right|thumb|150px|Small erosions of MDV/BVDV - vesicles are microscopic (Courtesy of Alun Williams, RVC)]]

===Pathology===

===Pathology===

[[Image:Bvd2.gif|right|thumb|150px|Coalescing lesions of BVDV (Courtesy of Alun Williams, RVC)]]

[[Image:Bvd2.gif|right|thumb|150px|Coalescing lesions of BVDV (Courtesy of Alun Williams, RVC)]]