Q: What is white line disease?

A: The white line is the area on the ground surface of the foot that appears as a narrow ring at the outside of the sole but inside the rim of the hoof. Infection occurs here when this area is weakens and a cavity develops, which separates the outer hoof wall from the laminae, allowing bacteria to enter. It arises generally in wet conditions, especially when the wetness is preceded by a long dry spell. It also occurs in horses who are stabled for large parts of the day, as the ammonia in urine can erode the hoof tissue and soften it. Sometimes white line disease can also be a sign of poor-quality hoof horn due to a nutritional deficiency, and occasionally it is due to a penetration wound or bacterial infection in the white line itself.

Clinical signs of the condition include:

  • Widening of the white line at the edge of the sole
  • Discolouration of the white line
  • Lameness
  • Sensitivity to hoof testers
  • Occasionally in severe cases, pus can be seen escaping at the coronary band.

Treatment of the condition involves rest; cleaning and trimming of the hoof to restore correct balance; the removal of the diseased tissue (or as much of it as possible); the draining of the pus or the opening of a channel through which it can be encouraged to drain; and improvement of the diet.