Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

White Line Disease, Seedy Toe

Synonyms: Dystrophia Ungulae, Hollow Foot, Hoof Wall Separation Syndrome or Disease, Onchyomycosis, Stall Rot, Submural Erosive Lesions of Hoof, Wall Thrush


White line disease is degeneration and separation of the attachments between the outer hoof wall and the underlying structure of the hoof. The cause of this disease is still debated but is likely due to agents that breaks down the normally tight attachments, the laminar layers. Once this happens, bacteria and fungal agents invade and digest the attachments, continuing the process up under the wall toward the coronet.

Genetics, poor nutrition and environmental factors all likely play a role in this condition. In addition, this disease often occurs secondary to another illness or injury. If the disease process has not progressed to the point of lameness, it is often discovered by a farrier during routine trimming. In advanced cases of this disease, it is often accompanied by laminitis.

In mild cases, treatment involves regular soaking and cleaning. In advanced cases, treatment may include ongoing removal of under-run hoof wall, application of topical agents, a hoof cast and corrective farriery. In either case, it is important to leave the hoof uncovered to expose the bacteria and fungal elements to air.

This disease is commonly known by a several other names. Under the name Hoof Wall Separation Syndrome (HWSS), a variation of this disease is thought to be caused by an autosomal recessive gene in Connemara Ponies.

my vet's role


Prognosis is good if this condition, and any other underlying conditions are recognized and treated early, but full recovery may take many months. Prognosis worsens if this disease is accompanied by laminitis.

my role


I might observe

You might make these observations when a horse has this condition.

Very Common
Less Common
more observations

Questions To Ask Your Vet:
  • How far has this disease progressed?
  • Is there any coffin bone rotation?

Good hoof care is key. Keep your horses feet dry and picked daily, and institute a routine trimming program with your farrier. Talk to your farrier about this disease and ensure that they carefully monitor your horse's feet and talk to you about any abnormalities.

further reading & resources

Related References:

Finno CJ, Stevens C, Young A, et.al. SERPINB11 frameshift variant associated with novel hoof specific phenotype in Connemara ponies. PLoS Genet. 2015;11(4).

Author: Doug Thal DVM Dipl. ABVP