BVD

Bovine viral diarrhea (BVD) is a viral disease of cattle and other ruminants caused by bovine viral diarrhea virus (BVDV), a member of the Pestivirus genus in the Flaviviridae family. BVDV has two main genetic types, BVDV-1 and BVDV-2, with multiple subtypes. The virus exists in cytopathic and noncytopathic biotypes; persistent infection of calves occurs when the fetus is infected during early gestation with noncytopathic BVDV, and the animal becomes a lifelong shedder of the virus.

Transmission occurs through direct contact between animals, contaminated equipment, or biological materials, and can also occur vertically from dam to fetus. Vertical infection during early gestation can result in immune-tolerant, persistently infected (PI) calves, which are a primary reservoir for virus in herds. Infected cattle may display a wide range of signs from subclinical infection to fever, nasal discharge, diarrhea, leukopenia, respiratory disease, or reproductive failure. In PI animals, subsequent infection with a cytopathic BVDV strain can lead to mucosal disease, which is typically fatal.

Diagnosis relies on detecting BVDV or its antigens, especially in newborn calves’ ear notch tissue, or by PCR testing of blood or tissues. Serology can indicate exposure but vaccination and maternal antibodies can complicate interpretation. Management emphasizes identifying and removing or segregating PI animals, implementing biosecurity measures, and employing vaccination strategies as part of herd programs. Vaccination may use modified-live or inactivated vaccines and is not a stand-alone substitute for PI control.

Economic impact includes reproductive losses, fetal abnormalities, immune suppression, and reduced productivity, leading to substantial losses in cattle industries worldwide.