Hoof abscesses

Definition

Who has never had a whitehead pimple under the skin? The starting point is an infection. It all begins with an area of the skin becoming red, often painful and hot, signs of an inflammation, which then becomes a small pocket of pus which becomes more and more painful as it swells. What a relief when it bursts ! It is the same process for an abscess in the horse’s hoof, except that the hoof horn is not as supple as our skin… the pressure which is generated in the hoof is therefore very painful for the horse, especially as he is constantly supporting himself on it!

What are the causes of a hoof abscess?

There are different types of cause to hoof abscesses, but they all have in common a weakening of the hoof capsule:

• Traumatic causes:
  • A shock (due to a stone for example) or a foreign body penetrating the sole (small, sharp object like a nail) can lead to a crack, localised bruising of the horn (bruise), or even a puncture wound, which allows bacteria to enter the sole, and then become emprisonned.
  • A problem when shoeing => Close nails in a shod hoof can injure the internal, more sensitive parts of the hoof (in the same way when we clip our nails too short or a splinter gets stuck under a nail). After an initial inflammatory phase, the injury can evolve towards an abscess in the days following shoeing.
• An environnemental cause:
  • During prolonged wet periods (e.g. horses accomodated in muddy fields or paddocks over the winter). The horn softens and becomes more permeable for the entry of bacteria, especially near the white line (the junction between the sole and the hoof wall).
  • During alternating dry and wet periods, the horn dries out, then softens again etc which causes cracks and fissures to occur.
• Intrinsically due to the horse itself :
  • Poor qualityhorn in some horses, making it more brittle.
  • Hoof conformation => Flat feet increase the risk of shocks to the sole.
• Poor management of the feet => Long feet and sunken heels weaken the white line for example. These are factors which increase the occurence of abscesses.

How does an abscess form?

Since it is extremely painful, a hoof abscess will frequently cause sudden, severe lameness, which can sometimes be impressive (the horse won’t touch the afflicted foot to the ground). This is the main clinical symptom. However, lameness can sometimes go undetected and/or get worse as the abscess matures, starting off with slight lameness, worsening to severe lameness when the abscess is close to bursting and the pressure within the hoof becomes too high. This acute phase usually only lasts a few days, until the abscess bursts. Pain then recedes very quickly.             Due to the intense nature of the lameness, several other symptoms may be observed, which are characteristic of inflammation:

• The foot is hot.
• Increased digital pulse (in a healthy foot, the digital pulse is only faintly perceptible) which can be felt by placing your fingers over the arteries which are located on either side of the pastern (known as the «digital palmar arteries»).
• The leg can be swollen, from the pastern to the fetlock, sometimes even up to the cannon.

In some cases, an injury around the hoof may be noticeable, but this is not always the case.

When the abscess is «ripe» and it begins to burst, a fistula (hole/ small channel) forms to evacuate the contents of the abscess away from the hoof. Grey to black pus running out is then noticeable, often accompanied by a strong stench.

Depending on the horse’s sensitivity, hyperthermia may be observed (usually moderate => T> 38,5° C ) associated with general listlessness and loss of appetite.

The hoof tester

Carried out with a hoof tester, this test consists in applying pressure to the different areas of the hoof (sole, frog, heels, coronary band…) so as to find the precise location of the abscess. In a healthy horse this test is not painful. If the horse reacts to the pressure of the tester at a precise location, there is a good chance that the abscess is located there.

Differential diagnosis

If doubt remains after using the hoof tester, the vet may decide to conduct X-rays of the hoofconcerned to confirm diagnosis. This additional examination will ascertain that the bone structure has not been affected (case of a severe abscess, with a bone infection, or arthritis) and to eliminate any other possible pathology, such as a fracture of the third phalanx.

Treatment is fairly simple: it consists in draining it, then subsequently keeping the hoof in a clean environment until completely healed.

Treatment of a hoof abscess is a collaborative treatment between the farrier (or the veterinarian in severe cases) on the one hand, and the horse owner or keeper on the other hand. It is generally advisable to start by unshoeing the horse.

Two possible situations…

Depending on the stage where the abscess is detected, management and care can differ slightly.

Either the abscess is ripe, and draining is all that is require

Once the abscess has been located with the hoof tester, the farrier will dig the horn out, with a hoof knife, until the pocket of pus is found. A small opening is all that is needed, but the hole should be open enough to allow complete drainage of the fluid.

If the abscess is maturing, and is not yet ripe

To this end, apply damp, warm, cooked linseed or a ready for usewet poultice to the sole, and/or to the hoof wall. Then wrap the foot in in a band of cotton wool and bandage it up with vet wrap to maintain the poultice in place.

The poultice should be changed every day until the abscess bursts. But how do you know when? Generally speaking, the stench when changing the poultice, and the black-grey pus will give you a good indication. It is also obvious that the horse rapidly becomes more comfortable.

Once it has burst : disinfect and leave the horse until completely healed

When the abscess bursts, the main thing is to keep the hoof in a clean, healthy environment to avoid any further bacterial infections. To acheive this, all that is required is to wrap the foot in an antisceptic soaked bandage (bleach for example) maintained with vet wrap. The bandage should be renewed every day until healing is complete. The owner/keeper therefore has an important part to play in the treatment of an abscess.

The horse should also be left at rest in a dry environment, again, until healing is complete.

In severe cases, where the sole is damaged for example, the farrier may use a specific shoe with a plate to avoid having the damaged area in contact with the ground.

How do I know when the horse is healed?

This is very easy : an abscess is considered healed when the bandage comes away clean, with no fluids, and when the horse is no longer lame.

Prognosis depends on the degree of the infection. If the abscess is rapidly and well taken care of, the horse will recover quickly, with no lasting damage, prognosis is good in this case. However this affliction should not be taken lightly, as complications are possible when treatment is not adapted, or when the infection is deep (bone affected…). In this case the prognosis may be more reserved.

The best way to prevent abscesses is to take regular care of the horse’s feet and to keep an eye on his environment:

• Pick the horse’s hooves and brush them out every day to remove any foreign object which could bruise the sole. It is also the opportunity to check on the state of the hoof horn (cracks, bruising…) and to check the state of the shoes (loose nails...)
• Implement regular upkeep of the hooves through :
  • Regular trimming (shoes renewed every 4 to 6 weeks for shod horses).
  • Apply hoof oil (use a grease, tar or oil from natural products) reasonably (2 to 3 times a week will generally suffice) so as to maintain strong healthy horn and prevent any cracks forming.
• Limit wet conditions as much as possible:
  • Change the bedding in the stable regularly.
  • Poo-pick the paddocks on a regular basis.
  • Avoid using wet or muddy fields or paddock.
  • Move the hay racks to avoid creating muddy areas around the feeding zones, or stabilise these surfaces.
  • Only shower the legs when necessary, and dry them off after showering.
  • Oil or grease the hooves before showering or before riding out in wet conditions (never oil over wet feet).
  • Avoid unshoeing a horse in the middle of winter (hooves more fragile, and the holes left by the nails provide an entry for bacteria)..
• Remove any sharp or pointed metal objects which could end up in the fields or in the tacking up areas..
• Keep horses with poor feet shod (thin or brittle sole, flat feet, horses who are regularly subject to abscesses…)..
• Keep an eye open for any hoof disorders which can make them prone to abscesses : split hoof wall, whIte line disease, thrush….