The viral diarrhoae virus

Pestiviruses consist in a single strand of positive sense RNA. Bovine Viral Diarrhoea Virus (BVDV), classical swine fever (CSF) and border disease virus (BDV) in sheep are also members of the pestivirus genus which belongs to the Flaviviridae family (like hepatitis C). BVDV, which induces mucosal disease in bovine, causes economic losses in cattle.

Many countries have started eradication programs for this disease, which involve a perfect management of infected animals. Indeed, those must be detected earlier with a high reliability. However, the prenatal infection of a calf between the 60 th and the 120 th day of gestation leads to the birth of a persistently infected (PI) animal. These infectious animals are seronegative all their live and positive by virology (antigenemy) only several weeks after their birth. This fact is caused by the persistence of colostral antibodies. An earlier detection of these persistently infected animals is necessary in eradication programs. Since the discovery of DNA in vitro amplification in 1985 (PCR), many scientists have developed virus screening tests using genomic amplification of the RNA also called RT-PCR (Dünser and al., 1999). Most of these tests allow the detection of minute quantities of BVD virus in blood or organs of infected animals, even if animals are less than three months-old.