Abstract

Teladorsagiosis is a major production-limiting disease in small ruminants in temperate regions throughout the world and is currently controlled using anthelmintics; however, resistance to Class I to III products is rife and multi-class resistant isolates have been reported. As an alternative method of control, we have developed a recombinant vaccine for Teladorsagia circumcincta which, when administered to 6-7 month-old lambs in two separate trials, significantly reduced nematode egg output. During the period of peak worm egg shedding, vaccinated lambs shed 92% and 73% fewer eggs than did adjuvant only recipient lambs, respectively. As well as protecting older lambs, one of the key interventions in the management of the disease is the prevention of pasture contamination with T. circumcincta eggs by ewes during the periparturient relaxation in immunity (PPRI) which occurs in the period around lambing. We have immunised 3-4 year old twin-bearing ewes with a T. circumcincta recombinant subunit vaccine and measured the impact that vaccination has on their immune responses and shedding of parasite eggs during a continuous T. circumcincta challenge period spanning late gestation and lactation. In ewes which displayed a clear periparturient relaxation in immunity, vaccination resulted in a reduction in mean cumulative faecal egg count compared to control (immunised with adjuvant only) ewes suggesting that, by immunising ewes to reduce susceptibility to infection during the PPRI , an important route of transmission of T. circumcincta could be blocked. To optimise the recombinant vaccine further and exploit it commercially we have developed a strategy to understand the nature of the vaccine-induced immunity and to tailor the key vaccine components accordingly. This approach and it’s outcomes will be presented.