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Seeking answers for skin disease in draft horses
Researchers look at genetics, management techniques for chronic progressive lymphedema


DVM360 MAGAZINE


Disease management

Practitioners are advised to counsel owners of draught breeds to inspect their horses' pasterns below the tufted hair down to the skin around each leg from the tarsal or carpal joint distally, feeling for grape-like bumps and folding lesions, which often are apparent above the line of the pastern feathering.

The feathering not only may somehow potentiate the disease, but mask its presence as well. Regardless of its potential hereditary transmission, it seems draft horses that are kept pastured in very moist/damp/wet conditions and lacking good animal husbandry present with faster disease progression. It might be a good husbandry practice to blow-dry the lower limbs and keep their stall bedding clean and dry.

"The lower-leg swelling is caused by abnormal functioning of the lymphatic system in the skin, which results in chronic lymph edema, fibrosis, a compromised immune system and subsequent secondary infections of the skin. Based on preliminary research, it appears that a similar pathogenic mechanism is involved in the disease that affects these specific draft horse breeds," according to the group at UC-Davis,

"Effective management of the disease is more successful or, in some cases, only successful if the pastern feathering is clipped," but many owners with show horses don't want to clip the feathering, Affolter says.

"The association of poor circulation, decreased lymph drainage, hyperkeratosis and occlusion by dense, long feathering present the perfect environment for opportunistic infections to settle in", and the feathering can interfere with topical treatment and with keeping the pastern region dry," she says.

Other recommendations include keeping the legs of affected horses clean and pristine, treating any infections, providing daily exercise, keeping the horses' legs dry and not leaving the animals outside in rainy weather.

"It seems that wrapping the legs with short-stretch bandages developed for humans with lymphedema has a positive influence on these horses," Affolter says. "The bandaging needs to be done correctly and under professional supervision. It must be padded well and put on with relatively high pressure. There will be a lot of oozing, especially the first week or so, because there is fluid permeating the skin."

DeCock and Van Brantegem wrapped two legs of an affected horse for three months. The result: the swelling, nodular lesions and ulcers diminished.

In a small follow-up study performed on six horses at UC-Davis, the results were not as positive, but those horses' legs were not clipped before the wrapping.

"It has to be emphasized that the bandaging is not a treatment, says Affolter. "As soon as the pressure bandages are no longer applied, the lesions will come back."

Affolter is in contact with people in England who are performing manual lymph drainage, which has been used successfully in horses with more acute lymphedema. It is expected that correct manual lymph drainage would also help keep CPL horses in better health.

The outlook

Equine practitioners and researchers at UC-Davis currently are collecting tissue samples from draft horses with CPL and from older draught horses without the disease to determine the molecular cause of CPL in a genomic-association study to be under way soon. "Ultimately, discovering the gene that causes CPL will help draft-horse breeders eliminate the disease from their breeding programs," says Amy Young, MS, a veterinary researcher at UC-Davis.

"We think CPL is associated with an inappropriate elastic support of the lymphatics," says Affolter. "It is so widespread in the affected breeds that it has to have a genetic background." However, there may be multiple factors involved. "We actually have a hard time finding non-affected draft horses once they are 10 to 12 years of age," Affolter says.

In addition to the work on the hereditary and genetic component, and work on learning how to manage the disease, the UC-Davis group looked at a possible nutritional component to the disease, because various trace nutrients are known to be associated with similar dermatological conditions.

"We have limited data, but we have looked at about 18 horses from a particular farm, and we evaluated zinc, magnesium, vitamin E, selenium and copper levels; they were all within normal limits," Affolter says.

Effect of leg wraps

"It seems that wrapping the legs with short-stretch bandages developed for humans with lymphedema has a positive influence on these horses. The bandaging needs to be done correctly and under professional supervision. It must be padded well and put on with relative high pressure," says Verena Affolter, DVM, PhD, Dipl. ACVP, University of California-Davis

Kane is a Seattle author, researcher and consultant in animal nutrition, physiology and veterinary medicine, with a background in horses, pets and livestock.


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Source: DVM360 MAGAZINE,
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