Mechanical Treatment for Hoof Wall Disease

© Tom Stovall, CJF

One of the most difficult things about treating Hoof Wall Disease (HWD) is that nobody knows exactly what causes it. We don't know for sure which pathogens are involved, aren't certain about the method of transmission, it's avenue of entrance, or much else: we do know its effect on the hoof wall and a simple method of treating the pathology. In an ongoing effort to add to the collective confusion of the industry, I figured I'd define the pathology as best I could, then offer my observations on stuff that works when it comes to treating the pathology. I'll also mention a new invention of mine in a patently transparent attempt to convince folks that it's the only thing to use in treating a variety of problems involving the loss of hoof wall.

HWD is thought to be a fungal infection of the stratum medium which is the middle (and largest) layer of the hoof wall. Unchecked, the infection can destroy the hoof to the extent that it is no longer able to support the horse. The infection is not painful as no enervated tissues are involved; however, as the stratum medium is destroyed, some lameness will be evident due to lack of support for the bony column. Evidently, HWD will not affect any structure with a blood supply: the infection will not attack either the sensitive structures of the hoof or the coronary band.

According to Burney Chapman (An AFA Journeyman Farrier who is active in HWD research), the pathogen(s) responsible for WLD is actually as many as three different fungi, possibly acting in synergy with other organisms.

Effective treatment is relatively simple. The consensus of the veterinary community on the Texas Gulf is that successful treatment must entail debriding all infected hoof wall and the creation of aerobic conditions at the infection site. If a significant amount of wall is removed, some sort of support shoe (usually a frog pressure ["heart"] bar) is applied, as is some type of hoof wall replacement prosthesis, to lessen the possibility of mechanical founder or sinking.

Chapman's first choice of topicals is benzoyl peroxide, although merthiolate or Durasole have been used with success. In a recent telephone conversation, he told me that it doesn't really make much difference what topical is applied as long as aerobic conditions are maintained at the infection site.

The conundrum facing veterinarians and farriers when dealing with HWD is that all infected hoof wall must be removed and aerobic conditions must be maintained. If not for the aerobic requirement, treatment would be simple: debride the infected hoof, replace it with a polymeric prosthesis and keep it clean. The necessity for aerobic conditions and medication precludes the use of most commonly used prosthetic polymers.

Chapman used to recommend 3M tape with drilled drains as a support prosthesis for severe cases, but 3M tape is no longer available. Various impermeable prostheses have been fitted with drains, but all have been unsuccessful in maintaining aerobacy at the infection site. The use of conventional, impermeable, polymeric prostheses is contraindicated because the prosthesis creates an ideal environment in which anaerobic organisms can grow and proliferate and does not allow the application of medication to the infected area.

I have recently been granted a patent for a gas/liquid-permeable polymeric hoof wall replacement prosthesis. It has been tested for three years and found to be an ideal hoof wall replacement prosthesis, especially when more than one foot is involved. By using this invention, the horse's weight is transferred from the hoof wall to the bony column as it would be by a normal hoof or conventional prosthesis; at the same time, the porosity of the prosthesis creates aerobic conditions proximal to the prosthesis and allows medication of the affected area through the prosthesis.

Frequently Asked Questions about HWD

Even if you resort to all of the above and cure the horse, won't he just become reinfected?
Not necessarily. The method of transmission has yet to be discovered. It is quite common to find a horse with WLD in one or two feet (not necessarily paired) with the others showing no evidence of infection.

Can be spread by the farrier's tools?
A study published in the Farriers Journal concluded that the method of transmission is not known.

Is it true that HWD is an opportunistic infection? That the organism is always around (in the soil?), and only becomes a problem when the conditions are right to support it's growth?
Chapman found that one of the bacteria sometimes found in association with WLD is often found in AIDS patients and others with impaired immune systems; however, most of the data suggests the cause is fungal.

Is it true that the shoe "seals" the white line and creates the anaerobic, moist environment that the organisms need to proliferate?
The shoe may help to form anaerobic conditions and the nails may offer an invasion site, but the moisture must come from the environment.

It certainly doesn't seem to be a problem in the barefoot beasts, can they get it?
Here on the humid Gulf Coast, HWD is very common in barefoot horses.

Why is it that HWD only becomes a difficult problem if it infects only a portion of the insensitive structures of the hoof?
HWD affects only the stratum medium of the hoof wall which has no blood vessels and no enervation, however HWD may facilitate the invasion of other pathogens which attack the sensitive structures of the foot.

In Summary

The greatest difficulty in treating HWD is that it can totally destroy the structural integrity of the hoof if not treated; i.e., HWD can render the hoof unable to support the horse. The dichotomy facing the farrier and veterinarian in treating HWD is that aggressive treatment by conventional means may render the animal just as unsound as no treatment at all. It is very difficult to explain to a trainer why his/her horse will miss an entire year of competition in order to effect a "cure".

When the use of gas/liquid permeable prosthetic devices becomes widespread, the extreme impact of HWD and other anaerobic infections of the hoof wall will be diminished considerably.

Tom Stovall is an American Farriers Association Certified Journeyman Farrier since 1983, a Member of the Texas Professional Farriers Association, and a Member of the Artists-Blacksmiths Association of North America. Thanks to him for his permission to post this article.

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