Ref.CDVB012
96 tests/kit
BVDV
Bovine
General Information
BVD Bovine virus diarrhea - and mucosal disease are two different
clinical disorders caused by the same virus. BVD is the result of acute
infection in susceptible animals. Onset may occur at any age after birth.
BVD has a brief course and low mortality. Muscosal disease, in contrast,
is a deadly disease of low morbidity. It develops in viraemic animals that
have been contaminated in utero. The characteristic of this in utero
infection is the existence of specific immunotolerance that prevents the
animals from producing antibody against the infective strain but not
against another, antigenically different BVD strain. These persistent
carriers can live for years without developing clinical signs of the
disease. The only way to detect them is thus to use laboratory screening
tests.
While the only valid method for detecting the animals with persistent viral infections remains identification of the BVD virus itself, it is possible to use a serotest to avoid having to subject all the animals of a farm to as cumbersome a test as the detection of BVD virus in the leucocytes. Indeed, one has the greatest chance of finding animals with persistent infections in a herd of perfectly seronegative animals. However, one should not forget that this group can also include animals that have never come in contact with the virus. Serotests also enable one to monitor the serological status of a herd that is being vaccinated and identify the animals that have been contaminated by monitoring the increases in their serum titers(seroconversions).
Principle of the test
The Cypress BVDV test uses 96- well Microtitration plates sensitized by monoclonal antibodies specific to one of the antigenic determinants of BVDV strain NADL. This antibody is used to trap the virus as well as to purify it from lysate of the cells in which the virus was grown. The plates’ odd columns (1,3,...11) contain the virus, whereas the even columns (2,4,.....12) contain a lysate of the line of Bovine testis cells that was used as a substrate to propagate the virus. We thus have a genuine negative control to differentiate the specific anti-viral antibody from the antibodies directed against the antigenic determinants of the testis cells used for its replication. Using such a control reduces the number of false positives considerably.
The test blood sera are diluted 1 : 100 in the buffer for dilution. The plate is incubated and washed, then the conjugate - a peroxidase labeled anti-Bovine IgG1 monoclonal antibody - is added to the wells. The plate is then incubated a second time at room temperature and washed again and the enzyme’s substrate (hydrogen peroxide) and the chromogen tetramethylbenzidine (TMB) are added. This chromogen has the advantages of being more sensitive than the other peroxidase chromogens and not being carcinogenic. If specific BVDV immunoglobulins are present in the test sera the conjugate remains bound to the microwell that contains the viral antigen and the enzyme catalyses the transformation of the colorless chromogen into a pigmented compound. The intensity of the resulting blue color is proportionate to the titer of specific antibody in the sample. The signal read off the negative control microwell is subtracted from that of the positive microwell sensitized by the viral antigen. Comparison of the signals obtained for the unknown samples with those obtained for a reference serum, supplied with the kit, make it possible to rank the serums positivity on a five point scale.
Rev.09.95
