Further attempts to immunise lambs using metabolites and in vitro grown larvae of Ostertagia circumcincta.

Attempts were made to immunise lambs by the intramuscular injection of either lyophilised or concentrated metabolites produced by Ostertagia circumcincta when grown in vitro, or macerated fourth and fifth stage worms. The lyophilised metabolites did not stimulate protection against the establishment of worms in nine-months-old lambs but the macerated worms and concentrated metabolites elicited protection in six-months-old and three-months-old lambs respectively. The worm burdens and worm egg counts of the immunised lambs were less than those of control lambs.