Towards preventing digital dermatitis transmission between dairy cows

Background: Bovine digital dermatitis (BDD) is an infectious disease causing serious lameness in dairy cattle worldwide. This important disease raises the following issues for the UK dairy industry:
1. BDD is very painful, making it an important animal welfare issue. The disease is endemic on the majority of UK dairy farms, providing a real challenge for the dairy industry as a whole.
2. Considerable economic implications result from treatment costs and reduction in milk yield and reproductive ability. BDD is estimated to cost a dairy holding of 65 cows $1,517/year which equates to costing the UK dairy industry (1.85 million dairy cows) a substantial £26.4 million/year. More recently reported BDD associated non healing horn lesions as well as potential transmission to other farm animals would further exacerbate these costs.
3. Spirochetes (bacteria) belonging to the genus Treponema have been identified by several groups as the primary causal agents of BDD. However, these organisms are very difficult to isolate and grow and there has been little success worldwide in obtaining relevant isolates, even though they are found in all BDD lesions.
4. The research team at the University of Liverpool (UoL) has been responsible for isolation and characterisation of a large number (100+) of bovine DD treponemes and for designating one phylotype as a new species; Treponema pedis.
5. As a result of BBSRC and AHDB funding we have previously identified or clarified several additional infections reservoirs of DD treponemes including the GI tract, foot trimming equipment and gloves
6. These data are compelling and provides a strong case for studies which identify means to prevent transmission of these bacteria through various routes. Thus, this project sets out to develop methods to prevent transmission both using field and lab-based studies.

Research Hypotheses and Objectives: The major hypotheses of this study are that a) using appropriate disinfection methods we can eliminate infection reservoirs of DD treponemes from foot trimming equipment and that b) using a biofilm model we can identify treponemal quorum sensing mechanisms and that quorum sensing inhibitors or other novel antibacterial agents may reduce DD treponeme viability and motility and be potential therapeutic and/or disease control agents.

The project ideally suits a PhD (48 months) study programme, with specific objectives as follows:
1) Investigate the survival of DD treponemes on cattle foot trimming equipment and develop appropriate disinfection protocols.
2) Use newly developed protocols on farm to verify elimination of the respective DD treponeme infection reservoir
3) Develop a biofilm model of DD treponeme infections and use transcriptomics to identify and characterise quorum sensing pathways.
4) Assess the impact of novel bactericide(s) and/or novel QS inhibitors (in comparisons with other disinfectants) on treponeme survival, motility and biofilms.

Rationale for the approaches taken:
Stewardship issues surround the use of antibiotics due to risk of antimicrobial resistance (AMR), together with environmental and safety concerns over key footbath solution components make current BDD treatment and control methods difficult to use going forward. This studentship is devised to provide additional routes that may allow for better control or even elimination of BDD from farms.