Wet and muddy conditions soften the foot and allow bacteria to gain access through the white line, which is the junction between the sole and the hoof wall. It is a natural line that delineates the hard, non-sensitive part of the foot, or the hoof wall, and the sensitive structures of the foot, or the laminae.
Cracks in the hoof wall or minor traumas to the sole of the foot add to the increased risk of the horse developing an abscess in these conditions. Once the bacteria enter the hoof, they multiply and cause the production of pus, which builds up into a pocket, causing pressure and pain until an exit point is found and the pus can escape. Ideally, this involves the farrier or veterinarian locating the site of the abscess and using a hoof knife or similar piece of equipment to open the abscess, allowing pus to drain down through the sole. Often in cases where the horse does not receive any farrier or veterinary care, the pus will find the easiest path for drainage, the one with the least resistance, up through the coronary band. This is not ideal as the pus needs to track upwards to be discharged, and once the pressure has been released, it can be difficult for the pus at the lowest point inside the hoof to drain.
HOW DO I KNOW MY HORSE HAS A FOOT ABSCESS?
Most horses with a hoof abscess will show a lameness that progressively gets worse over several days until the horse becomes severely lame, sometimes even non-weight-bearing lame. Clues that indicate the foot may be involved include: the horse standing with a front foot stretched forward of the body (front foot abscess) or the horse taking weight on the toe of the affected foot while standing or trying to walk. With hind feet, the horse can hover the affected foot just above the ground before it places the foot down.
On closer inspection, the foot is warm or hot to touch, and for those able to palpate a pulse, a bounding pulse can be felt. As the lameness progresses and the infection builds, there is often swelling of the lower limb, predominantly from the coronet up through the pastern to the fetlock. In some cases, the swelling can move up into the cannon area towards the knee as the infection moves from the abscess and into the soft tissues of the limb. Hoof testers can be used to help localise the site of the abscess as the horse is usually sorest where the pocket of the infection is located. This can take a bit of finesse to detect as certain horses can show response all around the foot and careful, fine application to different areas may be required for the sorest area to be defined. On some occasions, multiple abscesses in more than one foot can occur and this can make diagnosis challenging, as the horse appears to have difficulty in walking or will not walk, and other causes must be ruled out.
WHAT DO I DO IF I THINK MY HORSE HAS AN ABSCESS?
The obvious answer is to seek professional advice, either from a farrier or a veterinarian. Unfortunately, this is not always possible. Until the abscess has been opened, or burst, the horse will usually remain lame. If veterinary or farrier attention cannot be sourced initially, then the foot should be soaked in warm, salty water to encourage the abscess to come to a head. This makes it easier to open if a qualified person can attend the horse or allows it to burst through the coronary band and promote drainage through this opening. If the abscess does burst of its own accord, then the hoof should continue to be soaked for several days to ensure that all the infection has completely drained.
The use of commercially available poultices has taken over from the practice of soaking the foot, however, in some cases, soaking the foot can provide better results, particularly in the more stubborn cases where the abscess cannot be opened or can take an extended period to burst on its own. I would typically soak the affected foot twice a day in salty water (often using Epsom salts), as hot as the horse will tolerate, which usually means as hot as the human hand can stand. Povo-iodine can be added to the water to act as an antiseptic, but I have not always found this necessary. Once the foot has been removed from the water and dried, apply a poultice to the hoof, so the area is kept clean and the abscess encouraged to drain/burst.
I am often asked if the poultice should be put on wet or dry. In the initial stages the poultice should be moistened with warm to hot water, as a poultice needs the moisture to draw. The disadvantage of continuing to use a wet poultice is it can make the sole waterlogged and predispose it to other conditions. Similarly, continuously applying a wet poultice to the coronary band can cause damage to this structure, so a balance needs to be found. Applying a wet poultice for a couple of days, then a dry one to allow the coronary band to dry, often works well. Once the abscess is open and pus is draining from the area, a dry poultice can be used, as the pus will wet the poultice and encourage more drawing of pus onto itself. As the abscess resolves, there will be less discharge onto the poultice, which has a self-limiting effect on its drawing ability. If in any doubt as to how the abscess is resolving, seek the advice of a veterinarian or a farrier.