THE EFFICACY OF AN INACTIVATED IBR VACCINE IN THE PREVENTION OF INTRAUTERINE INFECTION AND ITS USE IN A DISEASE-CONTROL PROGRAM

The effects of administration of an established, inactivated IBR vacci ne were studied in 30 cows from two herds (one seropositive and one se ronegative). All acquired immunity which, after subsequent intratrache al infection with IBR virus, prevented development of symptoms in the cows and protected their foetuses against viral infect-ion in utero. T he calves were all healthy and were born at normal term. Ten non-vacci nated cows from the seronegative herd responded to the experimental in fection with mild respiratory disease and abortion of four out of 10 f oetuses. Organs from the aborted foetuses were found to have IBR virus . In a breeding herd, without clinical signs of disease but with 40 % of cows tested as seropositive, a 2-year disease-control programme was initiated. A total of 234 newborn calves were examined and it was sho wn that immunization of their darns with an inactivated vaccine confer red full in utero protection against IBR-virus infection. When such ca lves are reared in isolation they can be used as the nucleus for a ser onegative breeding herd.