Bovine Viral Diarrhea (BVD)
Northeastern US: Bovine Viral Diarrhea (BVD) in dairy cattle.
A large dairy farm with multiple heifer raising facilities had a raised suspicion of BVD in the herd, as one heifer facility had deviated from the vaccination protocol. There were clinical signs compatible with BVD on the farm, including 2 bred heifers that had late term abortions, and a calf that died and had histologic lesions consistent with BVD. The farm started aggressive BVD testing of the entire herd. Detection of persistently infected (PI) animals was performed by submitting ear notches from all nonlactating cattle (youngstock and dry cows) for BVD Antigen Capture ELISA (ACE) to the Animal Health Diagnostic Center (AHDC).
BVD Bulk Tank milk string samples from the lactating cows were submitted to the AHDC as well, which includes BVD PCR and Virus Isolation on each sample. Seven bulk tank string samples were submitted and three tested positive. (One bulk tank sample can have a maximum of 400 cows in it). Each cow in the positive pools of milk was subsequently ear notched for BVD ACE testing. One PI cow-calf pair has been identified. PI cows always give birth to PI calves, but normal cows exposed to BVD virus at ~60-125 days gestation will give birth to a PI calf. The cow may then clear the virus and develop an antibody titer, but she will not become a PI herself.