White Line Disease is the classic chicken or the egg scenario.  Which came first?  Unbalanced feet, improper trimming, poor conformation?  Or could it be excessive moisture, poor circulation, or stress?  Or is it actually White Line Disease?
White Line Disease (WLD) begins as a soft, powdery area along the hoof wall or sole junction.  Left untreated, it will turn into a black, greasy substance on the inner layer of the hoof, nail holes, or cracks in the hoof wall.  WLD is more prevalent in warmer, humid climates, although cases are increasingly being reported in all areas of the country.  A misnomer about WLD is that it is caused from poor hygiene.  This is absolutely not true.  The exact cause is still being discussed by professionals all over the world and no one has the answer.  In other words, Oprah Winfrey will have the answer to WLD on a TV special during Super Bowl Weekend next year.

Many signs can indicate WLD - dishing, flares, tender soles, shelly feet, or lost shoes can all be warning signs.  Careful observation by your farrier is critical to detect signs of the disease before it becomes a soundness issue.  Soundness issues become apparent when the disease has compromised the integrity of the hoof wall and it separates from the coffin bone.  A horse with undetected and advanced WLD will often move similarly to a foundered horse.  WLD in all feet could indicate a nutrition problem, an immune deficiency, or poor circulation due to age, stress, or lack of exercise.

White Line Disease affects all breeds and horses of all ages.  Older horses are more susceptible and harder to treat, likely due to lack of exercise and poor circulation.  If left untreated, these pathogens will deteriorate and destroy hoof walls.  WLD weakens the foundation of the hoof, leading to poor angles, imbalances, and lameness.
Treatments for White Line Disease are as varied as the disease itself.  Sometimes the treatment can cause more damage then the disease.  When your farrier or veterinarian wants to resection an area, keep in mind the weight of the horse must still be supported by the amount of hoof wall that is left after the debridement.

In the above photographs, so much hoof wall was debrided that the hoof wall collapsed, causing serious lameness issues for this horse. The case photographed below has supported the hoof wall with a cast until new horn can grow.

When a horse under your management has WLD, make sure that you understand what treatment will be done and ask questions about the proper procedure for the amount of WLD your horse has. And remember, if a debridement is recommended and a temporary support system such as Equicast is not discussed, chances of hoof wall failure increases relative to the amount of hoof wall that has been removed.  When a large area of WLD has been found, careful cleaning and treating with silver sulphadiazine has worked extremely well in areas with high temperatures and humidity.

Anyone who would like to discuss WLD or any other hoof related issue with me can send photos and a case history to AskDave@equineherald.com.