Changes

===Laboratory Tests===

===Laboratory Tests===

There are several techniques available for the laboratory diagnosis of BVD.  

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

Laboratory tests for BVDV include virus isolation and assays that detect antibody in serum or detect viral RNA or viral antigen in clinical specimens and tissues. Because antibody against BVDV is prevalent in most cattle populations, a single serologic test is seldom sufficient for diagnosis. A >4-fold increase in antibody titer in paired serum samples obtained 2 more weeks apart is necessary to verify recent infection. Isolation of BVDV from blood, nasal swab specimens, or tissues confirms active infection. Identification of persistent infection requires detection of virus in clinical specimens obtained at least 3 wk apart. At necropsy, tissues of choice for viral isolation include spleen, lymph node, and ulcerated segments of the GI tract.

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. ELISA

Alternatives to viral isolation include antigen-capture ELISA from blood or serum, immunohistochemistry to detect viral protein in frozen or fixed tissues, PCR to detect viral RNA in clinical specimens, and PCR or in situ hybridization to detect viral RNA in fresh or fixed tissues. Differentiation of viral genotypes usually is done by PCR or PCR followed by nucleic acid sequencing. Monoclonal antibody binding assays and nucleic acid hybridization assays also differentiate viral genotypes.

 

Serum neutralisation depends on the ability of antibodies in

the serum to neutralise BVD virus and thereby prevent

infection of cell culture. The test usually takes four to seven

days to obtain a result but is dependent on cell culture

facilities and an experienced observer.

ELISA

An enzyme-linked immunosorbent assay (ELISA) technique

An enzyme-linked immunosorbent assay (ELISA) technique

for BVD virus antibodies that depends on binding of antibody

for BVD virus antibodies that depends on binding of antibody

takes one day. It requires purified ingredients but is simple to

takes one day. It requires purified ingredients but is simple to

operate and the results can, if necessary, be recorded by eye.

operate and the results can, if necessary, be recorded by eye.

Detection of virus

 

 

 

Detection of virus viral RNA or viral antigen in clinical specimens and tissues

Cell culture

Cell culture

BVD virus can be cultivated in cell culture monolayers (eg,

BVD virus can be cultivated in cell culture monolayers (eg,

plates or small petri dishes can be identified by enzyme-linked

plates or small petri dishes can be identified by enzyme-linked

antibody. This assay may take only three to four days.

antibody. This assay may take only three to four days.

===Pathology===

===Pathology===