Fighting White Line Disease

Untreated white line disease can undermine your horse’s feet, causing lameness and coffin bone instability.

No account yet? Register


White line disease sneaks up on you without warning–one day your horse is fine, and the next day the farrier is digging a crater in your horse’s foot, dumping what seems like handfuls of soft, crumbly hoof horn on the floor. You might ask, what the heck is white line disease? Why is it such a big deal? Your horse isn’t even lame, although you fear he might be soon with that new crater in his foot.

This ugly mess called white line disease might not be a big deal initially, but left untreated it can undermine large amounts of your horse’s foot (or feet), resulting in lameness and instability of the coffin bone within the horse’s foot. Bill Baker, DVM, of Equine Associates in Hawkinsville, Ga., discussed the disease and its treatment at the recent Bluegrass Laminitis Symposium, held Jan. 25-28 in Louisville, Ky.

"White line disease doesn’t seem to occur without some sort of mechanical stress (such as long toes or hoof damage from previous disease or injury)," he began. "The only known certainty (about its cause) is that a breach in the hoof wall has to occur for the disease to occur. (Opportunistic bacteria and/or fungi then invade the defect and begin destroying hoof wall from the inside, starting at the bottom and working their way up.) There is no breed, age, or sex predisposition to this disease. It occurs in anything from Minis to drafts, donkeys, and mules. It may invade one foot or all four feet.

"Most cases are diagnosed with physical exam findings," he went on. "You see a small breach or crack in the hoof, explore it a little with a hoof knife and find cheesy, soft, white horn. You explore further and find that lots of wall is undermined. That soft white horn is why it’s called white line disease, although that’s somewhat of a misnomer because it affects the white inner part of the stratum medium layer of the wall (just outside the white line). It doesn’t really affect the zona alba (white line) at all."

He noted that the disease initially causes no lameness at all, and that typically a farrier will see this during routine trimming long before a veterinarian will be called. If a veterinarian is called, he/she can radiograph the feet to see how far up the hoof wall the separation has progressed.

White line disease is best battled by resecting (cutting away) the affected area of the hoof to expose the bacteria and/or fungi to the air, said Baker. He recommends shoeing to support the reduced area of hoof wall available for weight bearing after resection. Various medications/disinfectants are also commonly used; he discussed all of these options in turn.

Resection/shoeing "Most people are resecting all abnormal tissue, and if you do that, you better support the foot," said Baker, noting that this was his preferred approach. "You can’t take the wall off if you don’t support the horse. This is one of the most critical parts of any white line disease treatment.

"Some resect, then rebuild the foot with hoof repair material," he continued. "But in my experience, when you pull (the repair material) off, the disease is still there. I don’t cover the resection unless I have to; I let them grow out on their own. This is why a radiograph is so handy to help you decide what mechanics you’re going to need for that foot (because it lets you see how far up the damage goes)." He added that antibiotic-impregnated hoof patches have been unsuccessful because they are not effective against the fungi that are often present in affected feet.

Cast the feet He noted that some people will resect the hoof, cast the foot to provide support, then medicate under the cast. Shoes can be nailed into the casting material for further support. "You can put a felt pad under the cast and leave a little sticking out, so you can apply medication to the felt and thus medicate the area every day," he commented.

Gas the feet Chlorine dioxide is often used in food service to clean vegetables and food processing areas, said Baker, and it has also found some favor in treating white line disease. The theory behind its use for affected horses is that when mixed with vinegar, chlorine gas is produced that can permeate the wall and kill the bacteria/fungi without having to cut away the wall. It is applied once or twice weekly to the foot via a boot or bag for up to 45 minutes, he explained.

Baker reported that several studies have found some success with this method, but none have directly compared it with resection alone, so it’s not possible to say if it’s a better treatment without further study.

"I think you better catch it pretty darn early if you want to get that stuff all the way up the hoof wall," he commented.

Medications/disinfectants "There are a ton of white line disease medications out there," said Baker. "Most people are using Merthiolate (thimerosal, an organomercury compound used as an antiseptic and antifungal agent) or iodine as disinfectants, and there are antibiotics and antifungals. Some studies have had poor success with antibiotics because they don’t kill the fungi. Antifungals have some benefit, but they can get very expensive."

Medication trial Baker discussed a medication trial at his clinic using 21 horses from five to 23 years of age, including five mares, 15 geldings, and one stallion. All the horses (which were of various breeds) had been diagnosed with white line disease in both front feet. Each had one foot treated with resection and support shoeing only, while the other was resected, medicated with Fungidye (a broad-spectrum fungistat for treatment and prevention of infections), Merthiolate or 5% benzoyl peroxide, and supported. Five weeks later, he said, there was no difference between medicated and unmedicated feet in terms of disease recurrence, quality of new hoof, or time to return to soundness.

Baker summarized this disease and its treatment with the following comments:

  • There is no clear pathogenesis for white line disease, but there has to be some mechanical stress in the hoof wall for this to occur.
  • The best treatment starts with supporting the foot. Do not resect without a plan for support!
  • Exposure appears to be the best treatment. Apparently whatever’s causing this likes a low-oxygen environment. 
  • No medicines on the market have been proven effective. 
  • Research is much needed for this disease. 
  • Treatment is effective if early and aggressive.


Written by:

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from

Sponsored Content

Weekly Poll

sponsored by:

What lameness issues has your horse experienced? Select all that apply.
192 votes · 380 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form