White Line Disease
The white line is the narrow, light-coloured band visible on the underside of a freshly trimmed hoof at the junction of the hoof wall and the sole. White line disease, an infection that causes separation of the wall, may be seen first at the white line but actually affects the zone of contact between the hard outer hoof wall and the middle layer of hoof tissue. It occurs most commonly in front feet but can occur in any foot. The old saying, “No foot, no horse” might well have been coined in reference to this serious problem, which can lead to months of intensive treatment. In severe cases, lameness may develop. Left untreated, white line disease can result in rotation of the coffin bone due to widespread damage in the supportive structures of the hoof.
Causes
White line disease has been recognized for years and has accumulated names such as seedy toe, hollow foot, wall thrush, and stall rot. Despite its long history, the unknown factors exceed what is understood about the condition. It is not clear, for instance, whether the cause is fungal or bacterial, or possibly a combination of the two. Anaerobic organisms have been found in affected tissue, but aerobic strains have not been eliminated from consideration. It has been suggested that some type of stress (faulty hoof conformation, flexor deformities, concussion on hard ground, leverage created by overly long toes, or the combination of an overweight horse and small hooves) causes the laminae to tear and bleed. This trauma may provide a growth center for soil-dwelling bacteria or fungi that enter the hoof through cracks or nail holes
White line disease may be diagnosed during a routine trimming when a farrier notices a small area of crumbly or powdery black or gray tissue at the white line. Paring away the damaged horn reveals separation of the hoof layers leading upward from the toe toward the coronary band. Tapping on the hoof wall over the separation produces a hollow sound. Bulges or sunken areas of the hoof are sometimes noticed. The horse is usually not lame at this stage.
Treatment
