Efficacy evaluation of a Haemonchus contortus antigen-containing vaccine (Wirevax®) in sheep in South Africa

Abstract

This study was conducted to confirm the protective properties of the Moredun H. contortus antigen-containing vaccine Wirevax® administered to protect sheep against H. contortus infection by demonstrating that faecal egg counts and worm burdens are significantly lower in vaccinated animals compared to non-vaccinated animals. Serum samples were collected and antibody titres were measured. It was expected that the protective effect of the vaccine would last at least four weeks after the last dose of vaccine had been administered. After three vaccinations, given three weeks apart, the experimental vaccine Wirevax® stimulated a strong circulating antibody response. Statistically the mean antibody titres of the vaccinated sheep were significantly higher than those of the control sheep. The immune response was associated with reductions in faecal egg counts and worm burdens in vaccinated sheep when compared to unvaccinated control sheep. After the third vaccination, the efficacy of the vaccine was 86.93% and faecal egg counts were reduced by 95.59%. Thirty days after the last vaccination, the efficacy of the vaccine was 80.66% and faecal egg counts were reduced by 80.6%. It can be concluded that three vaccinations given at three-week intervals will aid in the control of H.contortus infections in sheep and will prevent new infections for a period of 30 days. Statistically, body weight did not correlate significantly with vaccination.