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

目前对控制绵羊蹄疾的建议包括接种疫苗。蹄疾是由革兰氏阴性厌氧菌结节双歧杆菌引起的，它被归类为10个血清组；A-I和M是基于菌毛基因的遗传变异而引起的，菌毛提供了运动性和粘附性。在英国，有一种商业上可用并获得许可的Footrot疫苗，Footvax，包含9个血清组。抗原竞争意味着随着疫苗血清组数量的增加，疫苗的效力会降低。发表的同行评议的科学文献提供的证据表明，与商业疫苗相比，使用较少的节瘤螺旋体血清组可以产生更持久的保护和更少的临床疾病。在澳大利亚，最近采用的一种策略是，希望接种疫苗的农场提交脚拭子样本，以确定其鸡群中存在的足蹄类血清群。一旦确定，就提供含有在该鸡群中发现的单一血清群的疫苗。同时使用最多两种血清组疫苗。该项目的目的是确定有针对性的血清组疫苗接种是否比商业上可获得的疫苗更有效地减少英国鸡群中的脚步流行率。更有效的疫苗接种策略将导致减少对抗生素治疗蹄疾的依赖，并对绵羊福利和农场利润产生积极影响。将在鸡群内设计和进行试验，以调查在拥有两个或更多血清群的鸡群中进行血清群特异性疫苗接种的效果。拭子样本将被用来分析接种血清组特定疫苗和商业足步疫苗后结节螺旋体载量和血清组的变化。将分析接种疫苗对羊群跛行流行率、生产力、抗生素使用和随后的盈利能力的影响。将估计国家一级抗生素使用的潜在减少量。

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.