Epidemiological studies into the role of serogroup-specific vaccines to control footrot in sheep

Current recommendations for the control of footrot in sheep include vaccination.
Footrot is caused by the Gram-negative anaerobe Dichelobacter nodosus which is classified into ten serogroups; A-I and M based on genetic variation in the fimbriae gene which provides motility and adhesion. There is one commercially available and licensed vaccine for footrot in the UK, Footvax, containing nine serogroups. Antigenic competition means that as the number of vaccine serogroups increases, the efficacy of the vaccine reduces. Published peer-reviewed scientific literature has provided evidence that using fewer serogroups of D. nodosus results in longer lasting protection and less clinical disease in comparison to the commercial vaccine.
In Australia, a recently adopted strategy is for farms wishing to vaccinate to submit foot swab samples for determination of the footrot serogroups present in their flock. Once established, vaccine is provided containing a single serogroup found in that flock. Up to two serogroup vaccines are used concurrently.
The aim of the project is to establish if targeted serogroup vaccination is more efficacious than the commercially available vaccine in reducing footrot prevalence in English flocks. A more effective vaccination strategy would lead to reduced reliance on antibiotics for the treatment of footrot, and a positive outcome for sheep welfare and farm profitability.
Within flock trials will be designed and conducted to investigate the efficacy of serogroup specific vaccination in flocks with two or more serogroups. Swab samples will be used to analyse changes in D.nodosus load and serogroup following vaccination with serogroup specific and commercial footrot vaccine. The impact of vaccination on flock lameness prevalence, productivity, antibiotic use and subsequent profitability will be analysed. The potential reduction in antibiotic use at a national level will be estimated.