Pus in the foot – a common problem but why does it happen?
Hoof abscesses (Sub solar abscess/ Pus in the foot) are one of the most common causes of severe, sudden onset lameness in horses.
A hoof abscess is defined as a localised accumulation of purulent exudates (pus) located between the germinal and keratinized layers of the hoof wall. It is the inflammation and the increased pressure exerted on the sensitive tissues by the fluid accumulation, which causes the clinical signs.
Hoof abscesses can occur in shod and unshod horses. There is no age, sex or breed predilection. They occur when foreign material i.e. gravel, coupled with infectious organisms i.e. bacteria, gain entry through the hoof capsule (epidermis) and initiate an abscess within the inner subsolar/ submural tissue (dermis).
Infection can enter the hoof in one of three ways:
- Through a break or fissure in the sole wall junction (white line)
- A misplaced nail or a puncture wound somewhere in the solar surface of the foot
- Through a full thickness hoof wall crack or multiple old nail holes.
- Severe lameness, often comparable to that caused by a fracture. Horse may not be able to fully weight bear on limb.
- Heat in foot and distal limb.
- Bounding digital pulse present.
- Associated distal limb swelling.
- Systemic signs of infection i.e. Fever/ lethargy if deeper structures are involved.
- Draining tract can sometimes be visible at the coronary band.
- Observation of clinical signs
- Application of hoof testers – a focal painful area can usually be identified, but not always.
- Foot radiographs can be taken in more chronic cases to help identify a gas or fluid pocket.
- Remove shoe if present.
- Careful Paring of the sole and frog to try and localise the tract – Care must be taken to NOT damage good, healthy tissue. The white line is the main area that is pared away as paring of other areas can result in the prolapse of sensitive corium leading to protracted pain.
- Aim to establish drainage of the abscess.
- Foot poultices and hot water footbaths with Epsom salts are used to help soften hard horn and localise the affected area if pus cannot be obtained initially.
- If pus is obtained (grey/black malodorous liquid) from the infected tract, the tract will be enlarged just enough to allow good irrigation and drainage.
- If the tract extends from the solar surface to the level of the coronary band, through and through lavage can be established.
- Once drainage is established, the foot needs to be kept clean and dry in either a foot bandage or poultice. The foot should continue being soaked in either iodine or Epsom salts daily until the infection and inflammation have been eliminated.
- Once infection is controlled, the defect can be packed with an antiseptic soaked swab and the foot bandaged until the defect has keratinised (hardened off).
- Shoes can be replaced when the area is dry and keratinised (hardened off).
- If large areas are affected, plastic pads can sometimes be placed under the shoe for solar protection or hospital plates can be used.
- Pain relief in the form of anti-inflammatories e.g. Equipalazone/ Metacam may sometimes be warranted.
- Antibiotics are RARELY needed and are usually contraindicated as they can prolong clinical signs and prevent the abscess from draining. Antibiotics are only ever used if infection is severe or deeper structures have been penetrated.
- Ensure horse is covered for
- If the abscess is left untreated, it will take the path of least resistance up the white line and eventually burst out of the coronary band. This will lead to a permanent scar under the hoof wall and may result in the following:
- Prolonged recovery time
- A chronic draining tract
- Repeated abscesses
- A full thickness hoof wall crack
Excellent prognosis, however prognosis decreases if complications develop in which deeper structures of the foot are involved.
The key is to promote a strong, solid, sole-wall junction (white line) that resists the penetration of debris. This is achieved with good trimming by your farrier and a good diet containing Biotin, Zinc and Methionine. This can be achieved using our Hoof Supplement.
Conditions that cause mechanical breaks or weakness in the continuity of the white line are:
- Excessive toe length
- Hoof capsule distortions i.e. Long toe-under run heels, excessive toe length, heels too high or a club foot, sheared heels.
- Hoof capsule separations i.e. white line disease, seedy toe
- Chronic laminitis
- Changes in the ground conditions i.e. Dry Wet Dry
Excessive dryness or moisture may also contribute to weakness in the white line.
- The use of hoof hardeners i.e. Keratex and stabling the horse on shavings/ saw dust may be useful to harden the feet during extremely wet weather.
- The use of hoof dressings painted onto the entire foot may be helpful to soften the capsule during dry weather.