Bovine viral diarrhea (BVD)

Characteristics of bovine viral diarrhoea virus (BVDV), such as its genetic diversity and ability to induce a persistently infected (PI) carrier state, make its control a challenge. A systematic control programme that utilizes diagnostic testing strategies to identify PI cattle, vaccination to increase fetal protection from infection, and biosecurity to reduce the risk of exposure to infected animals is necessary for control of BVD. The primary reservoir for BVDV is PI cattle. If a herd has had recently confirmed PI calves, or if the history strongly suggests the presence of PI calves, then all calves, replacement heifers, bulls, and nonpregnant dams without calves should be tested for PI status. Positive cattle should be removed prior to the start of breeding. Because of the low prevalence of herds with PI animals, whole-herd screening protocols for herds at low risk for PI cattle may not be justified. Several strategies short of whole-herd screening can be employed to monitor herds for the presence of PI cattle. Biosecurity to reduce the risk of exposure to BVDV should also be implemented. Replacement heifers and bulls should be tested and confirmed PI-negative prior to the start of breeding. If a pregnant animal is purchased, she should be segregated until both dam and calf are confirmed PI-negative. Fence line contact with neighbouring herds should be avoided during early gestation unless they also have a strict biosecurity programme in place. Vaccination to reduce the risk of fetal infection in the event of exposure to a BVDV-shedding animal is an integral part of a biosecurity programme.