Passive protection of newborn calves against rotavirus by vaccination of their dams.

The rotavirus is considered as being one of the major causes of acute gastroenteritis; it occurs in cattle farms where, either by itself or in association with other pathogenic agents, it is responsible for a high percentage of neonatal morbidity and mortality. Over two consecutive years, field trials were done using inactivated rotavirus vaccine in oily excipient inoculated to pregnant cows. Results obtained prove a significant increase in the rate of colostral antibodies and a very real prolongation of the excretion of these antibodies into the milk up to and over 28 days post-calving. From the clinical point of view, outbreaks of diarrhoea in calves born of vaccinated cows were less common and less serious, but more importantly, the rotavirus was found to be playing a far less significant role. It was thus demonstrated that the presence of a great quantity of specific antibodies in the intestine plays a protective role. This mechanism was the origin of the concept of lactogenic immunity and is particularly well demonstrated by the study of viral excretion at the virulent challenge of calves having followed differing lactation programmes.