Contagious Ovine Digital Dermatitis
Also known as: CODD
Introduction
Contagious Ovine Digital Dermatitis is an apparently new, severe condition causing lameness in sheep, first reported in 1997. The aetiology remains unclear but it is associated with the presence of spirochaetes similar to those found in bovine digital dermatitis.
Differentiating CODD from classic foot rot can be difficult in some cases.
Clinical signs
Acute lameness is the primary presenting sign, and the affected foot is often carried.
The primary lesion starts at the coronary band with rapid invasion and underrunning of the hoof wall from the coronary band downwards. This can result in complete shedding of the horn capsule of one or several claws. Regrowth of horn can be permanently affected.
There is sometimes loss of hair above the coronary band but usually no interdigital involvement.
Usually only one claw on one foot is affected.
Diagnosis
Diagnosis can be made if the characteristic progression of clinical signs is present.
However diagnosis can be made difficult if the lesions do not follow a pattern or if there is concurrent foot root infection.
The response to conventional treatment can help distinguish between CODD and foot rot, as CODD cases may fail to respond.
Microbiological examination can be carried out in suitable anaerobic conditions, and failure to demonstrate the organism responsible for footrot Dichelobacter nodosus might indicate CODD is present. However this is rarely performed.
Treatment and prevention
Conventional antibiotic treatments are usually ineffective in cases of CODD, but it might be worth test-treating animals with long-acting oxytetracycline and zinc sulphate footbaths before resorting to unlicenced treatments in case it is just a case of virulent foot rot.
Tilmycosin injections have been shown to be effective in treating CODD although they are an expensive option.
Antibiotic footbaths with lincomycin/spectinomycin or tilmycosin can be used once or twice at 48-hour intervals.
If the feet have been permanently damaged by the disease, culling might be the best option.
Prevention: Effective prevention of the more common reasons for lameness in sheep such as scald and foot rot may help reduce the incidence of CODD. This includes: pasture management to avoid excessive damp areas, regular footbathing, regular examination of the flock, prompt separation and treatment of affected sheep, culling chronically affected sheep, quarantine of replacement stock.
References
Winter, A. (2004) Lameness in sheep: Diagnosis, treatment and control, In Practice 26: 58-63 and 26: 130-139
Aitken, I. (2007) Diseases of sheep, Wiley-Blackwell
Hindson, J., Winter, A. (2002) Manual of sheep diseeases, John Wiley and Sons