Transient benign osteopetrosis in a calf persistently infected with bovine virus diarrhoea virus.

A two-day-old Simmental calf was admitted suffering from a fracture of the right femur. The radiographs showed striking changes in all bones, evident as alter-noting zones of dense and less dense tissue (bone-in-bone) in the right femur and striped densities in the vertebral bodies. A stainless steel plate was used to repair the fracture, which healed well. The calf developed normally but was diagnosed as persistently infected with bovine virus diarrhoea (BVD) virus. It was kept in isolation and examined physically and radiographically during the following 13 months. The radiographic changes diminished during the first three months and at 13 months were barely visible. The animal was euthanatized, and immunohistochemistry revealed BVD virus antigen in numerous tissues. The radiographic abnormalities seen in this case are similar to those of the transient form of osteopetrosis in humans. Osteopetrosis in humans is currently thought to have a genetical cause, whereas it appears to be associated with viral disease in animals.