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What is Chronic White Line Infection?

Where the wall of the equine hoof meets the sole of the foot is a fibrous unpigmented area that connects the two; this area is called the white line. When this area becomes infected, usually by a fungal or bacterial infection, it can trigger the deterioration of the internal tissue of the hoof. Chronic or severe infections can eventually lead to the rotation of the coffin bone in the foot of the horse if it remains untreated, and if an infection of the white line is suspected, veterinary assistance should be sought.

Chronic fungal or bacterial infections to the junction between the sole of the horse’s foot and the wall of the hoof can lead to the deterioration of the hoof itself.

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Symptoms of Chronic White Line Infection in Horses

Catching an infection of the white line is a matter of diligence as the horse rarely shows any signs of pain or distress until the damage to the structures of the hoof is significant. It is often caught by the farrier rather than by the horse’s owner or veterinarian and highlights the importance of proper hoof care. Common signs that a horse has developed a white line infection can include:

  • Brittle and dry external hoof wall
  • Bulges or sunken areas on the hoof
  • Crumbling horn tissue in the hoof
  • Hollow sound when hoof is tapped
  • Separation of the hoof wall

Types

There are several treatment options that can be used to clean and disinfect the hoof for proper healing: 

  • Apple cider vinegar - Apple cider vinegar diluted 50/50 with water is a mild solution that can be used as a spray on a daily basis; it is also helpful as a weekly foot soak to counter any developing fungus
  • Bleach - Diluted to a ratio of approximately 1/10 for either spray use as a hoof soak
  • Commercial products - Most commercial products are mixed with white vinegar and placed in a closed bag around the hoof
  • Lysol or Borax - These can be dissolved in water in order to soak and disinfect the hooves
  • Wire brushing - Wire brushing has also proven to be very effective at maintaining health in cases of chronic white line infection

Causes of Chronic White Line Infection in Horses

A fungal or bacterial infection of the white line can be triggered by a number of circumstances. Bacterium and fungus can be difficult to eradicate in the hoof, and the condition often becomes chronic. Some situations that can predispose a horse to this type of infection may include: 

  • Abnormal hoof structure
  • Abscess
  • Improperly balanced hoof
  • Injury to the hoof
  • Overgrown hooves

There is also some evidence that infections of the white line are more common in wet or humid conditions.

Diagnosis of Chronic White Line Infection in Horses

The successful diagnosis, treatment, and aftercare for an equine with a chronic infection of the white line is a collaborative effort between yourself, your equine veterinarian, and your farrier. The farrier is often the first one to notice that anything is amiss as the symptoms may not be obvious to the layman until the condition is quite advanced. During the examination by the farrier, any bulges or sunken areas will be evaluated, and a quick tap on the hoof with the farrier’s hammer will produce a characteristic hollow sound. 

An opening will be made in the hoof wall-sole junction in order to better visualize the affected area, and a crumbling, cottage cheese like black or gray substance will be found in the area. Standard blood tests may be run to determine if there is a systemic infection or any abnormalities or imbalances to be found, and some of the damaged tissue may be cultured to determine which fungi or bacteria has caused the infection. X-ray imaging will be used to ascertain the extent of the damage within the hoof itself.

Treatment of Chronic White Line Infection in Horses

The veterinarian and the farrier will work in close collaboration to come up with the best treatment plan for your specific situation. The bacteria and fungi that most frequently exploit this junction in the hoof are anaerobic, which means that exposure to oxygen will help to reduce their growth rates. To do this, a support shoe will be applied first to prevent uneven pressure to the hoof wall that will be remaining after the resection of the outer hoof, and then the farrier will cut away the wall of the hoof over the damaged areas.

The veterinarian will debride the underlying wound to remove any dead tissue and then thoroughly cleaned to remove any bacteria or fungi on the surface and to wash away any remaining powdery residue. The resectioned area will remain exposed during the healing period, which is frequently a lengthy process. Systemic infections sometimes stem from the original white line disease and if standard blood tests indicate that this has occurred then antibiotic or antifungal medications will be prescribed as well. It is crucial that the patient receives the full measure of their antimicrobial drugs in order to prevent the infection from reoccurring.

Recovery of Chronic White Line Infection in Horses

The prognosis for horses that have developed this condition depends on how much decay has resulted inside the hoof, the adherence to the treatment protocols, and the strength of the infection. If caught early enough that resectioning is restricted to the bottom half of the hoof then the horse is able to be lightly exercised and sometimes ridden, however, animals who require resectioning above the halfway mark may need to take some time before stressing the foot. Instructions from your veterinarian will typically include daily cleaning of the wound, and it will also need frequent medical debriding until the infection is eradicated and the hoof has grown back out.