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6.4 Virus isolation PDF Drucken E-Mail
 

Virus isolation in cell culture is the gold standard of testing for BVD virus. Viral antigen is then identified immunohistochemically. BVD virus, in principle, grows in a number of animal cells, although in diagnostic procedures it is mainly three cell lines that are used: BT- (bovine turbinate cells) Btest- (bovine testicle cells) and MDBK (Madin Darby bovine kidney cells). It is not possible to differentiate between acute and persistent infection after a single isolation. Virus isolation is time consuming and quite expensive and therefore not suitable for routine diagnostics. Preferentially, these days it is replaced by other methods.

 

Sample material

Suitable as samples are blood (EDTA or heparin blood) of live animals, or lymphatic organs (Peyer’s patches, mesenterial lymph nodes and thymus) of dead animals [87]. PI animals harbour such large quantities of virus that practically any secretion, excretion or tissue is suitable for virus isolation [88]. Different from its behaviour in cell culture medium, BVDV is fairly stable in diagnostic samples. The latter are sent to the lab cooled or frozen (after prior confirmation by telephone).

 

Identification

Cytopathic (cp) BVDV can be identified according to its destructive effect in cultured cells. Non-cytopathic BVDV (this is about 90% of all cases investigated in the lab) is made visible by fluorescent or enzyme-marked monoclonal or polyclonal antibodies.

 

Limitations

Virus isolation is a sensitive method - it works essentially with one replication-competent virus. However, in the case of young animals of less than 3 months of age false negative results are possible, caused by the presence of maternal neutralizing antibodies. It is therefore sensible to use virus isolation only in the case of older animals (> 3 months) [89].