Interdigital Dermatitis - Cattle

Also know as: Scald — Slurry Heel — Stable Footrot

Introduction

Interdigital dermatitis is caused by the anaerobic bacteria, Dichelobacter nodus.

This condition has been confused in the literature with foot rot. The clinical signs of the two diseases are distinctly different. Interdigital dermatitis (ID) is caused by Dichelobacter nodosus, however, different genotypes of this organism cause foot rot in sheep compared with those causing ID in cattle. Transmission of the disease between sheep and cattle has not been reported.

It is hypothesized that ID plays a role in the evolution of other diseases such as foot rot, digital dermatitis, and heel erosion. D. nodosus and Fusobacterium necrophorum have been consistently isolated from lesions. However, other organisms frequently present in the interdigital space also play a part in the progress of some of these diseases.

Interdigital dermatitis appears to be endemic in most countries wherever cattle are densely concentrated. Reports on the prevalence of the disease have come from the UK, Netherlands, and various other European countries. The condition is also recorded in Australasia and Argentina (Rutter, 1984) and it was identified in Canada by Hanna et al. (1994).

ID is a mild superficial infection of the skin between the claws. In most instances, ID is a benign condition rarely causing lameness and is not associated with a drop in milk yield, loss of body condition, or increase in body temperature. There is a low incidence of ID in cattle at pasture. However, infection can build up wherever the traffic in cattle is high. As the climatic conditions deteriorate in the autumn, the prevalence of the disease increases. ID is particularly prevalent when the feet of cattle are continuously bathed in slurry and is commonest during cold winter months, therefore by late winter some animals may be showing discomfort and pain-producing lesions may be observed.

The first stage of the condition appears to be a wet dermatitis of the skin between the claws. Secondly, fluid is produced by the disease process oozes to each end of the space between the claws and forms a crusty scab, which may be occasionally observed on the dorsal surface of the digits. Affected animals are not usually lame at this stage, although many paddle from one foot to another on their hind limbs. This is an obvious sign of irritation or itching. As the condition progresses, the heels of the hind feet start to erode and become quite raw. This stage can be painful; the animal shows signs of lameness and the hind limbs will be held further back than is normal. After a time, during which the animal has avoided bearing weight on the heel, the horn beneath the heel will increase in thickness. Finally, chronic irritation of the skin between the claws of dairy cows is the commonest cause of corns (fibroma) developing on one side of the space.

Signalment Cattle of any age, breed or sex are predisposed to this condition.

Clinical Signs Signs include generalised lameness or stiffness and limping on affected limbs. These limbs may also show signs of disuse atrophy in chronic conditions and swelling in acute conditions. The animal may be pyrexic and have a reduced milk yield or weight gain and may show signs of weight loss. It may be noted that the animal is at the back of the group and is unable to walk at usual speeds. There may be an ‘under-running’ of the hoof on close examination and a grey exudates which has formed a scab in the interdigital space, will be one of the first signs of the condition. Later the area may also be abscessed, brittle or cracked. There will be a foul odour from the foot.

Diagnosis Clinical signs and history, with a detailed lameness examination and physical examination of the hoof are indicative of the disease due to the characteristic appearance and location of lesions. Differential diagnoses include digital dermatitis and foot and mouth disease. These need to be eliminated and can be done so be detailed physical examination by an experience clinician. Laboratory diagnostic tools include the identification of Dichelobacter nodosus by immunofluorescence technology from smears of lesions.

Treatment and Control The use of systemic therapy, including antibiotics, is not warranted. In severe cases, the lesions should be cleaned and dried, after which a topical bacteriostatic agent should be applied; such as a 50% mixture of sulfamethazine (sulfadimidine) powder and anhydrous copper sulfate. Alternatively, an animal can be confined in a 5% copper sulfate footbath for an hour, twice-daily for a number of weeks.

Control measures include good husbandry, such as reducing the presence of slurry when cattle are housed in winter and enforcing or introducing housing systems that keep claws dry and clean are the most important. Regular foot trimming helps to avoid complications. Footbathing, commencing in late autumn and before clinical cases can be identified, is essential in herds known to be infected with Dichelobacter nodosus. Solutions of 3% formalin or 5% copper sulfate are usually effective. However, these chemicals biodegrade slowly; therefore, new products are being presented in the market. Weekly footbathing may be sufficient in the late autumn, but the frequency may have to be increased in late winter.

There is no vaccine currently available for cattle with this condition.