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White Line Disease in Horse's Hooves

By Katherine Blocksdorf, About.com Guide

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White Line Disease:

I've had two experiences with white line disease. My draft cross Freya was prone to it. My daughter's OTTB also had it, and for a while walked around with a large chunk of hoof wall missing. The area behind the hoof wall was separated from the laminae and to prevent further infection and problems the farrier removed the 'hollow' area. Although it's called white line disease, it's not really the white line that is affected. Rather it's the material between the wall and the white line that becomes infected.

Other Names for White Line Disease:

Seedy toe, stall rot, hollow hoof, wall thrush, WLD

Causes:

White line disease occurs when fungi and bacteria enter through a small separation of the hoof wall. The microorganisms consume the hoof material causing further separation. The initial separation may be caused by an improperly trimmed hoof that separates at the toe (most commonly). Grit or another foreign object may work up behind the hoof wall allowing an entry point for infection. Poor hoof conformation—such as a large horse who has very small hooves or a club foot, bad shoeing, contracted heels, a dirty environment and poor nutrition are all implicated in the formation of white line disease.

Symptoms:

If the horse is getting regular trims from a farrier, there's a good chance the white line disease will be discovered before any damage that would cause unsoundness occurs. As you are cleaning out the horse's hoof, the area between the hoof wall and white line (sometimes called the 'water line') may appear thicker and is easily pulled out with the hoof pick. What you pick out may be a dark colored powdery, mealy or slightly granular material. The area may also seep and smell somewhat like thrush. The horse may show signs of tender soles, the shape of the hoof wall may change and eventually the horse may show signs of lameness.

As the farrier trims the hoof and cleans up the sole, they may notice the change in the hoof and may find a hollow area under the hoof wall. Imaging may show the extent of the damage, and rule out other problems like laminitis.

Treatment:

When my daughter's OTTB had it, the farrier trimmed away the hoof wall over the hollow area, allowing it to dry and alleviating weight bearing and concussion in the area. Supportive material may be applied over the cleaned out area and but only after any signs of infection are gone. Topical antiseptics can help clear up any remaining infection. Shoes may be recommended to stabilize the hoof

After the hoof has been cleaned up it's important to keep the hoof clean and dry. This may mean keeping the horse stalled or in another pasture or paddock if conditions are muddy or wet. The horse may be able to return to work depending on how much of the hoof wall had to be removed. On our OTTB, the section removed was less than the width of my hand and extended about half way up the hoof. He was sound and was able to do flat work shortly after the white line disease was discovered. But in other cases, a lot more hoof wall may have to be removed. The open areas of the hoof may be packed with substances that prevent dirt and moisture entering and resist infection.

Prevention:

Because the exact causes of white line disease are so varied, it's difficult to do anything that will specifically prevent it from happening. Regular farrier visits, clean pastures and stalls and good nutrition are the most important elements of hoof health. Balanced trims will prevent heels from becoming under-run and toes that are too long that cause the hoof wall at the toe to separate from the underlying structures. In the case of my draft cross mare, our gritty soil was partially to blame and regular hoof trimming and frequent application of an antiseptic was required.