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White Line Disease
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From: tom.stovall@yob.com (Tom Stovall)
Date: 1 Jun 95 19:33:00 GMT
Please note: This post is intended for general information only and not
specific to any individual. As always, a veterinarian should diagnose and
treat any pathology. This FAQ will be updated on a regular basis.
White Line Disease FAQ
Tom Stovall, AFA Journeyman Farrier
(c) copyright 1995, all rights reserved
Diagnosis of WLD:
=My 9 year old thoroughbred mare pulled a shoe at a show and
=the farrier there said she had white line disease.
Diagnosis of *any* pathology is the province of a veterinarian, not a farrier.
=My own farrier has never mentioned this and he is usually very good.
=Could this other farrier be wrong?
Anyone can be wrong, especially when attempting to do another's job. On a
personal level, as a farrier of some experience, I easily recognize various
pathologies; however, I'm not paid to diagnose pathologies, I'm paid to shoe
horses. If, in the course of my labors, I see something that I think needs
attention, I advise the trainer to call a vet; if necessary, on an emergency
basis. If a vet determines that a pathology requires a special shoeing
technique, *that's* what I'm paid to do.
To reiterate: ask your vet, not your farrier.
Q: Can anyone tell me what exactly white line disease is and how it should
be treated?
Definition:
White Line Disease (aka, Fungal Onychomycosis) is thought to be a fungal
infection of the stratum medium which is the middle (and largest) layer of
the hoof wall. The infection will 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 boney column.
Evidently, WLD 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 WLD research) the pathogen responsible for WLD is actually three
different fungi, possibly acting in synergy.
Treatment:
The consensus of the veterinary community on the Texas Gulf is that
recommended treatment entails debriding *all* infected hoof wall, the
creation of aerobic conditions and the use of some sort of support
shoe/prosthesis (usually a frog pressure ["heart"] bar) if the removal of
hoof wall is extensive. Chapman's (and Texas A&M's) first choice of topicals
is 10% benzoyl peroxide, although merthiolate or Durasole (tm) may be also
be used.
The greatest problem facing veterinarians and farriers when dealing with WLD
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
recommends the 3M tape with drilled drains for severe cases, but the 3M tape
can only be used for one shoeing period because of the possibility of
pressure necrosis at the bulbs of the heels.
A liquid-permeable prosthetic polymer is being tested which, if successful,
will revolutionize the treatment of WLD.
Q: Even if you resort to all of the above and cure the horse, won't he just
become reinfected?
A: 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.
Q: Can be spread by the farrier's tools?
A: A study conducted by Dr. Ric Redden which was published in the _Farriers
Journal_ concluded that the method of transmission is not known.
Q: Is it true that WLD 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?
A: 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, preliminary data suggests the cause is fungal.
Q: Is it true that the shoe "seals" the white line and creates the
anaerobic, moist environment that the organisms need to proliferate?
A: The shoe may help to form anaerobic conditions and the nails may offer an
invasion site, but the moisture must come from the environment.
Q: It certainly doesn't seem to be a problem in the barefoot beasts, can
they get it?
A: Here on the humid Gulf Coast, WLD is fairly common in barefoot horses.
Q: Why is it that WLD only becomes a difficult problem if it infects only a
portion of the insensitive structures of the hoof?
A: WLD affects only the stratum medium of the hoof wall which has no
vascularity and no enervation, however WLD may facilitate the invasion of
other pathogens which attack the sensitive structures of the foot.
The greatest difficulty in treating WLD is that it can totally destroy the
structural integrity of the hoof if not treated; i.e., WLD can render the
hoof unable to support the horse. The dichotomy facing the farrier and
veterinarian in treating WLD is that aggressive treatment 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".
White Line Disease FAQ
Tom Stovall, AFA Journeyman Farrier
(c) copyright 1995, all rights reserved
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