Immunization of sheep against the larval stage of Taenia multiceps.

A trial with 200 ewes and 127 lambs showed that vaccination of lambs with 2 doses of Oncosphere Secretory Antigen (OSA) 4 weeks apart, at either 4-8 and 8-12 weeks or at 12-16 and 16-20 weeks of age, was equally effective in protecting them against infestation with the larval stage of Taenia multiceps. In this trial, the lambs of ewes, vaccinated with OSA when they were 90 and again 120 days pregnant, were as susceptible to infestation as the lambs of untreated control ewes. Another trial to provoke passive immunity in lambs gave inconclusive results. In a 3rd trial 2 doses of regular OSA and 2 doses of freeze-dried OSA protected all the lambs in each group, while a single dose of regular OSA protected 9 out of 10 lambs against cerebral lesions.