Cerebellar hypoplasia in calves is caused by infection in utero with which agent?

• A. In Utero Infection with BVD Virus
• B. Postnatal BVD Infection
• C. Bluetongue Virus Infection
• D. Rabies

Answer: (A)

In utero viral infection disrupting fetal brain development is what leads to cerebellar hypoplasia in calves. Bovine viral diarrhea virus (BVDV) is a classic teratogen in cattle; when the dam is infected during early gestation, the virus crosses the placenta and interferes with cerebellar development, producing calves with cerebellar hypoplasia. These calves often show ataxia, tremors, and a wide-based stance because the cerebellum didn’t form properly. If the fetus is exposed to noncytopathic BVDV early enough, it can become persistently infected and shed the virus after birth. Postnatal BVD infection wouldn’t cause a congenital malformation, and rabies isn’t known for causing fetal brain abnormalities. Bluetongue can cause fetal defects too, but the most well-established link to cerebellar hypoplasia in calves is in utero BVDV infection.