Congenital curly haircoat as a symptom of persistent infection with bovine virus diarrhoea virus in calves.

Ten calves were born small and with a curly haircoat in a dairy herd which comprised approximately 185 milking animals. These calves commonly developed diarrhoea and/or signs of respiratory disease at the age of 2 to 4 weeks. Two of the calves died and 5 were chronically ill and poor doers and were therefore euthanized. This susceptibility to disease of the curly haired calves was quite different from what was observed among other calves in the herd. Sera from seven of the curly haired calves were examined and were all found to be free from detectable antibodies to bovine virus diarrhoea virus (BVDV) and to harbour a non-cytopathic strain of BVDV. One of the calves was retested after 7 weeks and was still seronegative and viraemic. Of 49 non-curly haired calves examined in the herd 44 were BVDV seropositive. The other 5 were seronegative to BVDV but attempts to isolate BVDV from their sera failed.