Vaccination of lambs against Taenia ovis infection using antigens collected during in vitro cultivation of larvae: passive protection via colostrum from vaccinated ewes and the duration of immunity from a single vaccination.

Fifty Merino-cross ewes were vaccinated approximately four weeks before parturition with antigens collected during in vitro cultivation of Taenia ovis larvae. A further 50 pregnant ewes were sham-vaccinated at the same time. When the first 20 lambs from each group of ewes were one to two weeks old they were placed, with the ewes, on an experimental paddock heavily contaminated with T ovis eggs. After six weeks the lambs were killed and their total carcase musculature and hearts examined for cysticerci. The results showed that the ewes vaccinated in late pregnancy had conferred a very high degree of transcolostral immunity upon their lambs against the T ovis challenge infection. Eighty T ovis-free Merino-cross weaner lambs, four months old, were divided into two groups of 40. One group was vaccinated with T ovis culture antigens and the other group was sham-vaccinated. At intervals of one, four, eight and 12 months after vaccination 10 lambs from each group were allowed to graze on the plot contaminated with T ovis eggs. After six weeks the lambs were killed and examined for cysticerci of T ovis. The results indicated that the single vaccination had stimulated a high level of immunity which persisted for at least 12 months.