Rotavirus infections in calves: efficacy of oral vaccination in endemically infected herds.

A commercially available modified live reovirus-like (rotavirus) vaccine proved innocuous in calves deprived of colostrum and protected one out of three calves against challenge 72 h after vaccination. The vaccine was evaluated in two dairy herds in the 1977 calf season. No significant differences were observed in the incidence rates or severity of undifferentiated neonatal calf diarrhoea or rotavirus-associated late diarrhoea between calves given a placebo (76) and vaccinated (74) calves in these herds. Samples of colostrum contained specific antibodies against rotavirus and neutralisation of the vaccine virus by colostral antibody in the intestinal tract was considered the major reason for the failure of the vaccine to reduce the incidence of neonatal diarrhoea in these herds.