Acta Veterinaria Tomus XXIII, Fasciculus 1. [antikvár]

FOETAL ACTIVE IMMUNIZATION OF CALYES FOLLOWING INOCULATION OF THE DAM WITH A BOYINE VIRAL DIARRHOEA VACCINE (VÉDÉVAC)ByK. Bognár*Control Institute for Veterinary Serobacteriological Products (Director: Gy. Kucsera), Budapest(Received March 16, 1972)The observation that the calves born to cows inoculated with the live bovine viral diarrhoea (BVD) vaccine Védévac (Simonyi et al., 1967) during the second semester of preg-nancy possessed specific serum antibodies already prior to the intake of colostrum, was first described in a preliminary report in 1969 (Bognár, 1969). Since then, succesful protec-tion of pregnant cows and their offsprings by Védévac has been substantiated under field conditions by the clinical and epizootological observations of Koós and Berecz (1971) and Szabó (1971) in a herd exposed to BVD. This phenomenon of "foetal active immunization", which was initially demonstrated in the calves of a few cows only, is therefore now postulated to be generál in occurrence.The immunity evoked in the calves concerned must have arisen in the foetus, because according to the still valid assertion of Schneider and Szathmáry (1939), no antibodies can cross the chorio-epithelial placenta from the maternal into the foetal circulation.The stimulation of a foetal antibody response by BVD virus has been confirmed inde-pendently by three American groups. Ward et al. (1969) infected 11 serologically negatíve pregnant cows with virulent virus. Directly after parturition, three of the newborn calves showed symptoms of the disease, whereas four had developed serological antibodies to the agent and were not affected. Classick et al. (1970) infected a susceptible 4-year-old cow, previously checked serologically twice every year, with virulent B\ D virus and removed her foetus 33 days later by Caesarean operation. No virus could be isolated from the organs and lymph nodes of the foetus, but its serum contained specific anti-BVD antibodies. Finally, Kahrs et al. (1970) have described an outbreak of BVD in a cattle herd during which eight of 29 pregnant cows aborted and two calves developed cerebellar hypoplasia. Of 14 calves examined serologically, eight had serum antibodies prior to the intake of the colostrumThese data support my earlier conclusion that BVD virus can gain access to the bovine foetus and there, depending on its nature, either stimulate antibody formation or produce changes characteristic of the disease.While these other authors studied the effect of virulent BVD virus on the calf foetus, the experiments reported here were carried out with the aim of improving control of the disease, particularly with regard to the protection of calves which are exposed to virulent virus from birth onwards.