Authors

A Nisbet¹;  ¹ Moredun Research Institute, UK

Discussion

Developing recombinant sub-unit vaccines against parasitic nematodes in livestock has been a long-term goal for a number of researchers over the last few decades and has not yet yielded a commercial product. Of the parasitic diseases considered to be most impactful on sheep health and welfare – sheep scab, fascioliasis and parasitic gastroenteritis (PGE), there is only one vaccine currently available (Barbervax) and that is specific for Haemonchus contortus. PGE in temperate regions, however, is caused by the major endemic gastrointestinal nematodes (GIN) of sheep (Teladorsagia circumcincta, Trichostrongylus spp. and Nematodirus battus) and we have now developed a prototype recombinant sub-unit vaccine against the most common and important of these, T. circumcincta. This vaccine induced significant (up to 75% reduction in worm numbers) protection against challenge in lambs, was effective in periparturient ewes and a simplified prototype also gave good levels of protection. However, this novel vaccine has variable efficacy and can only target a single species of GIN, whereas adequate worm control requires multiple species to be repeatably targeted if the vaccine is to complement anthelmintic treatments. We have therefore developed strategies to improve efficacy and to reduce variability through understanding host:parasite interactions, developing novel delivery systems to stimulate the appropriate immune responses and we have begun to identify common protective antigens and/or peptide epitopes from multiple GIN and will, in future, test the efficacy of these “multivalent” vaccines delivered in a range of ways.