Unravelling the aetiology of contagious ovine digital dermatitis

1. New understanding of how CODD arises. In majority cases CODD arose from pre-existing ID/FR lesions, suggesting better control of scald and footrot should allow for better control of CODD also

2. CODD a polybacterial disease. Fusobacterium necrophorum, Dichelobacter nodosus, Treponema medium, Treponema pedis and Treponema phagedenis are all significantly associated with all stages and grades of infectious foot disease in the flock - Interdigital dermatitis (ID), Footrot (FR), and Contagious Ovine Digital Dermatitis (CODD)

3. Identified novel bacteria Porphyromonadaceae, Family XI, Fusobacteriaceae, Veillonellaceae are also associated with ID/FR/CODD

4. Infected flock, healthy feet, healed CODD feet and treated CODD feet can be colonized by some of Fusobacterium necrophorum, Dichelobacter nodosus, Treponema medium, Treponema pedis and Treponema phagedenis could also represent on going source of infection to the flock or spread to other flocks

5. Treatment of CODD, 91. 7% cure (3 weeks)

6. Digital Dermatitis Treponema can be detected both in the sheep environment and at the recto-anal juntion of infected animals. Suggests increasing hygiene where possible should reduce CODD transmission and the need for good biosecurity

7. Glove and hand disinfection. This is the first time that this fomite (hands/gloves) has been identified as an infection reservoir for CODD treponemes and control methods described. This is valuable knowledge together with previous work where we demonstrated foot-trimming knives as an infection reservoir

8. Maggots from CODD lesions contained DD treponemes whilst flies deriving from these larvae did not. This rules out the likelihood that the flies themselves are responsible for transmission

9. Armed with more knowledge on infection reservoirs of CODD treponemes it should now be possible to better limit the spread of treponemes on farm

10. Immunological data suggests infection is associated with an immune response to digital dermatitis treponemes and further work is needed to determine whether serology might be useful as a diagnostic - more work needed

11. Novel leg lesions in yearling lambs which may initiate through environmental trauma appear to have both Fusobacterium necrophorum and Streptococcus dysgalactiae as key to aetiology which should help inform treatment and control

12. A similar disease to CODD exists in dairy goats and this could mean similar control methods could be used in sheep and goats​

The Problem:

Current estimates of lameness prevalence in sheep flocks in England & Wales are 10% (Kaler et al 2008) with an estimated cost £24million per annum.  The Farm Animal Welfare Council has challenged the sheep industry to reduce lameness prevalence to less than 5% by 2016 and 2% by 2021. Until recently, research efforts have been focused on the control of one major cause of lameness, footrot. Consequently, most of the current evidence-based veterinary medicine lameness control advice based on footrot.

The emergence of contagious ovine digital dermatitis (CODD) as a major new lameness problem in the UK is a new and important challenge.  35% – 53% farms in England and Wales report CODD.  There is little current evidence based advice available for CODD control, which impacts on lameness control.

Aims and Objectives:

• Determine differences of the bacterial microbiome of feet between CODD and healthy sheep
• Identify temporal changes in bacterial microbiome of sheep’s feet during (and after) naturally occurring outbreaks of CODD
• Assess role of the immune response of sheep during naturally occurring outbreaks of CODD
• Measure the effect of systemic antibiotic treatment on the microbiome of sheep’s feet affected by CODD 
• Examine the local environment for presence of bacteria of interest.

Approach:

A group of store lambs will be sourced from a farm with no history of CODD.  Four lambs with CODD lesions will be introduced to the group and the lambs will be monitored daily for clinical signs of CODD.

All feet will be swabbed weekly for microbiological assessment and the lambs will be blood sampled monthly for immunological testing.

The lambs will be treated with antibiotics and foot and bacteriological monitoring will continue to look at the impact of treatment.