BOVINE VIRUS DIARRHEA MUCOSAL DISEASE - A REVIEW

Infections with the Bovine Viral Diarrhea/Mucosal Disease Virus (BVDV) are widespread and cause a variety of diseases including reproductive disorders, abortion and malformation, pneumoenteritis, thrombocytopen ia and mucosal disease. Together with the closely related border disea se virus of sheep (BDV) and European Swine fever virus (CSFV), also re ferred to as Hog Cholera virus, BVDV is now classified in the genus pe stivirus of the Flaviviridae family. The BVDV exists in two biotypes, noncytopathic and cytopathic, the latter differing in structural prote ins from the noncytopathic biotypes. In virus-free animals infection i s transient and mostly subclinical or mild but may also lead to an arr ay of diverse symptoms such as pneumoenteritis (often in combination w ith other microorganisms). Infection of the developing fetus early in gestation with a noncytopathic biotype of BVDV may result in persisten t infection and birth of apparently healthy calves. Such calves may la ter in their lives develop Mucosal Disease, a lethal course of infecti on associated with a mutation to the cytopathic biotype or superinfect ion with a cytopathic BVDV antigenically similar to the noncytopathic virus already present in these animals. Diagnosis of infections with B VDV is based on the clinical symptoms and demonstration of virus. Pair ed serum samples allow the detection of seroconversion in acute infect ions while persistently infected animals are immunotolerant and genera lly lack antiviral antibody. Although generally found in their respect ive host species, pestiviruses of cattle, sheep and pigs are capable o f crossing the species barrier into the other species. The existence o f pestiviruses in wild ruminants and boars may complicate control stra tegies that are aimed at removing virus carriers and the control of an imal movements.