Contagious Ovine Digital Dermatitis

An investigation into contagious ovine digital dermatitis lesion treponeme bacteria and their antibiotic susceptibilities

Project number:                    73108

Lead contractor:                   University of Liverpool

Start & end date:                   30 September 2013 – 29 September 2014

 

The Problem:

Contagious Ovine Digital Dermatitis is recognised by farmers and vets as a serious welfare and economic issue for many UK farmers (FAWC report 2011). Research conducted across Wales in 2011 demonstrates that CODD currently affects 35% of farms. Current approach to treatment relies on the extensive use of antibiotics, often in a whole flock strategy using antibiotics, and in particular, the macrolides group. These antibiotics are considered very important for human medicine and with current concerns over rising antibiotic resistance in humans and animals it is essential that antibiotic use in food animals is carefully considered.

 

Aims and Objectives:

1) To investigate the variation in treponeme bacteria found in contagious ovine digital dermatitis lesions from different farms.

2) To investigate the variation in antibiotic susceptibilities of treponeme bacteria from contagious ovine digital dermatitis lesions from different farms.

 

Approach:

This work is an extension an on-going epidemiology study of CODD being undertaken by the applicants and funded by the British Veterinary Association with the support of Hybu Cig Cymru.  This funding covers additional laboratory costs, as the staff and sample collection costs are already funded.

Treponemes will be isolated from CODD lesions from animals from the six Welsh study farms. The isolates purity and phylotype will be determined by 16S rRNA gene sequencing. Lesions will be subjected to treponeme phylotype specific PCR to identify the different treponemes present. The 18 isolates will then be subjected to antimicrobial susceptibility testing for ten different relevant antibiotics.

 

Results:

This study found that BDD treponemes (individually and collectively) are present in all CODD lesions examined and does provide further evidence for the treponemal associations with CODD. However this finding alone does not prove causality. Further investigations must include comparisons with healthy tissue, investigation of associations with other bacterial species and temporal associations with lesion development.

To date no antibiotic product has a license to be used to treat CODD. The antibiotics studied here were selected to include antibiotics that already have a UK licence for use in sheep (penicillin, amoxicillin, oxytetracycline and tilmicosin) together with those that in the researchers‘ experience are already used (off label) in the sheep industry.

Therefore, when taking current UK medicines legislation into account, and given these data as a whole, penicillin and tilmicosin would appear to be the most likely candidates for future clinical trials as a consequence of their efficacy and availability as licensed products for use in sheep.

This work has already been used in an EBLEX/HCC PhD studentship and is being tested within a second PhD looking at treatment options.