Bovine Viral Diarrhoea (BVD)

Is the most common viral disease, and the one with most economical and environmental impact in European bovine cattle breeding.

It is caused by the bovine viral Diarrhoea virus (BVDv), which belongs to the genus pestivirus of the Flaviviridae family.

Bovine viral diarrhoea virus (BVDv) causes a variety of clinical syndromes in cattle including respiratory disease, reproductive dysfunction, immunosuppression, persistent infection and mucosal disease. Unapparent or subclinical infection without any clinical signs that is followed by seroconversion is the most common form of infection in the field.

Acute clinical disease may range from mild disease of high morbidity and low mortality to severe enteric disease with considerable mortality. Clinical signs of disease usually are seen 6–12 days after infection and last 1–3 days.

Recovery is rapid and coincides with production of viral neutralizing antibody. Some isolates of BVDv have been associated with severe clinical disease that manifests with high fever, ulcerations at different sites, gastrointestinal and immune cells depressions.

In pregnant cattle, BVDv may cross the placental barrier and infect the fetus. Infection near the time of fertilization may result in reduced conception rates. Infection during the first 4 months of fetal development may lead to embryonic resorption, abortion, growth retardation, or persistent infection, which is an important sequela of fetal infection with non-cytopathic BVDv.

Persistently infected calf is one that is born infected with BVD virus and is a lifelong carrier and shedder of the virus, spreading millions of virus particles daily to the rest of the herd. Screening for PI using serologic tests to identify animals that lack antiviral antibody may not detect some PI cattle.