Hoof wall separation disease

The hoof of a foal with HWSD
HWSD causes the layers within the dorsal hoof wall (brown, far right) to separate from each other

Hoof wall separation disease, (HWSD), is an autosomal recessive genetic hoof disease in horses.[1] Research is being carried out at, among others, UC Davis School of Veterinary Medicine in Davis in California.[2] The disease has been found in Connemara ponies and was earlier referred to as Hoof Wall Separation Syndrome, HWSS.

Symptoms

The disease develops among foals from the age of one to six months and typically occurs during their first year of life.[3] The frontal edge of the hoof cracks and splits. Pieces of hoof wall chip off in bits. This cracking, chipping and peeling may involve the whole of the dorsal hoof wall. The deficit means that when the hoof wall reaches the ground (and weightbearing load) the wall breaks away from above the level of the sole. Thus the affected pony has to walk on the sole of the hoof with no support provided by the dorsal hoof wall. All four feet are similarly affected. This can be very painful for the animal, which may lead to the necessity of having the horse put down.[3] HWSD is often confused with white line disease (WLD) by those people who have no experience or knowledge of this genetic condition.

Origin and cause

The disease is an autosomal recessive condition, which means that both parents of the foal must carry the gene in order for the disease to hit their offspring.[2] The disease has been found in animals with a frameshift mutation variety of the protein Serpin B11.[3]

Distribution[4]
Healthy stallion Stallion with HWSD genes Stallion with fully developed HWSD
Healthy mare Healthy foals 50% healthy foals, 50% carriers 100% carriers
Mare with HWSD genes 50% healthy foals, 50% carriers 25% healthy foals, 50% carriers, 25% with fully developed HWSD 50% carriers, 50% with fully developed HWSD
Mare with fully developed HWSD 100% carriers 50% carriers, 50% with fully developed HWSD 100% with fully developed HWSD

Tests and treatment

Genetic predisposition may be confirmed through a DNA test.[1] There is no treatment as such, owners can attempt to manage the condition though various types of hoof care, and/or the use of special shoes. Such treatment is expensive and labour-intensive. Environmental conditions can make the condition worse (alternating wet/dry hooves). Protecting the hooves from such variations may reduce the effect of the disease.[4]

References

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