An estimated 50 per cent of UK flocks have cases of contagious ovine digital dermatitis.
Dawn Prime reports on the disease...
Lameness is still one of the biggest health issues affecting the UK sheep industry each year.
Fiona Lovatt, a sheep veterinary consultant at Flock Health, says it should be at the forefront of sheep producers’ minds as we head closer to winter.
Contagious ovine digital dermatitis (CODD) can be one of the reasons for lameness in a sheep flock.
CODD, which was first reported in the UK in 1997, is a severe infectious disease which causes considerable animal welfare and significant economic losses.
Mrs Lovatt says: “It is estimated that 50 per cent of the UK’s sheep farms have cases of CODD.
“Typically, the proportion of sheep affected in a flock is 2 per cent but can be as high as 50 per cent.”
CODD is caused by a bacterium known as spirochaete.
“This bacterium is similar to that which is responsible for digital dermatitis in cattle, which is a major cause of lameness,” she says.
Mrs Lovatt says there has long been questions about the connection between CODD lesions and the bacteria found in sheep footrot.
“Studies have shown an association between footrot and CODD,” she says.
“This could be because footrot and CODD bacteria are seen in the same environmental areas, or could be due to the skin barrier becoming damaged by footrot and providing a perfect environment for CODD to become a problem.”
Mrs Lovatt says there are five main grades of CODD.
“Grade one is the earliest stage of CODD, where the lesions are noticed by seeing ulcerations without hair loss, mainly at the level of the coronary band,” she says.
“At grade two there is ulceration of the skin at the coronary band, with partial under-running of the hoof horn, while grade three shows ulceration of the skin at the coronary band with the possible chance of the hoof horn being torn away.
“Grade four shows a healing foot, with the horn beginning to regrow but an active lesion can be seen.
“At grade five, the foot is healed, but very often you will see a deformation of the regrown horn.”
In order to diagnose CODD, Mrs Lovatt says it is essential that all lame sheep are examined immediately.
“Correct diagnosis is usually based on clinical signs and is vital for effective treatment,” she says.
“Your veterinary surgeon will confirm CODD and help prepare an individual lameness control plan for your farm. Veterinary advice is necessary so CODD can be diagnosed, instead of the numerous other foot diseases which can also be on-farm, such as a foot abscess which discharge at the coronary band, advanced footrot, and a foot granuloma.”
If CODD is left untreated, it can be a major welfare issue and even more challenging to manage. It may be difficult to distinguish CODD from other types of footrot, so early veterinary investigation is essential, to ensure correct treatment can be given.
“Remember, treatment protocols for footrot are not necessarily effective for CODD,” Mrs Lovatt says.
“Consult your vet and establish a treatment plan for your flock.
“CODD is a very painful condition, so an anti-inflammatory may be used to help relieve the pain and help with recovery of the disease. Application of antibiotics by foot baths and whole flock antibiotic treatments are not considered to be responsible use of antibiotics and should not be considered.”
Mrs Lovatt says elimination of CODD is possible from some flocks in the UK and it is recommended to involve your vet to make a specific and strategic plan to target this disease on your farm.
“The first line of prevention is to quarantine all bought-in sheep for at least three weeks before mixing them with the flock,” she says.
“This includes your own sheep returning from grazing.
“Not all sheep with lesions are lame. It is good practice to check all feet on arrival and keep observing for lameness.
“If you are in any doubt, keep them separate. Also footbath during the quarantine period.”
Mrs Lovatt adds the footrot vaccine has been helpful in reducing cases of lameness, but it is important to remember using this vaccine does not target CODD and it must be used within all other parts of a flock plan.
She also says it is important to avoid co-grazing with any lame cattle or with a herd which has a history of bovine digital dermatitis, as the bacteria in CODD is like that which is responsible for digital dermatitis in cattle.
“CODD is an infectious disease, so good biosecurity measures and farm hygiene plays a major role in preventing this disease,” she says.
“Remember to always clean and disinfect hands, gloves and equipment between handling sheep.”
Symptoms of CODD
■ Sheep will be severely lame and typically one digit on one foot is affected
■ Due to the lameness there is reduced grazing activity, which in turn will lead to a financial loss as the sheep can rapidly lose body condition
■ Initially, there is hair loss - normally 2-3cm (0.8-1.2 inches) above the coronary band, where the hoof joins the skin of the leg.
Over a few days, the lesions progress downwards to the toe, under running the hoof horn capsule. These lesions become red and very sore and, in many cases, the whole horn capsule may fall off
TREATMENT PLAN FOR CODD
■ Isolate affected sheep to help stop the spread of infection.
■ Treat affected sheep on an individual basis with a long-acting injectable antibiotic ideally within three days of the start of the symptoms – a prompt use of appropriate antibiotics at the correct dose and used in the right manner is very important.
Antibiotics such as amoxicillin and macrolides have been shown to be effective, although whatever is used must be prescribed by a veterinary surgeon and specifically for your flock.