What is quittor?
Quittor is an old term for a condition that involves death and destruction (necrosis) of the collateral cartilages of the foot (see our information sheet on sidebones), following an infection in the foot (see our information sheet on pus in the foot).
While infection, i.e., pus in the foot, remains the most common cause of day-to-day lameness in the horse, quittor, a more serious complication, is now very uncommon. Quittor more commonly affects the front rather than the hind feet and the condition was more frequently seen in the heavy (draft) breeds of horses than the lighter breeds and ponies.
What causes quittor?
The collateral cartilages have a poor blood supply and so when infected they respond poorly and the infection becomes chronic and damaging. The condition seen in draft horses was known as 'treads' because horses pulling loads in teams would tread on the feet of the horse to their side. Draft horses frequently wore large caulks or studs on their shoes and this resulted in damage to the skin over the coronary band which introduced infection into the cartilages.
Quittor is still occasionally seen usually following external trauma to the foot, e.g., wire cuts, or interference injuries to the pastern and coronet. It may very rarely be seen as an extension from a sub-solar abscess (see our information sheet on pus in the foot).
How can quittor be diagnosed?
An intermittently discharging wound develops on the inside or outside of the hoof over the collateral cartilages, following an injury. The area is frequently warm, swollen and painful, consistent with infection. A number of small discharging sinuses (holes) may appear in the pastern over the collateral cartilage.
Lameness may be intermittent, varying from mild to very severe, but the horse may or may not be lame at the time of examination, because lameness usually subsides after the infection discharges ('breaks out').
Long-term cases may result in deformity of the hoof wall.
Radiographic (x-ray) examinations of the horse's foot may reveal necrosis of the sidebones and/or gas shadows, confirming infection, or ossification of the collateral cartilages (see our information sheet on sidebones), depending on the stage of the condition.
The condition may be confused with the much more common pus in the foot (see our information sheet on pus in the foot).
How is quittor treated?
Cases of quittor usually respond to long-term topical (placed onto the area) and systemic (given by mouth or injection) antibiotic drugs that are active against both aerobic and anaerobic infections. Quittor frequently recurs some time after the treatment is discontinued, because:
- the collateral cartilages have a poor blood supply and the drugs may not be delivered to, and penetrate, the infected site in the necessary concentrations to completely eliminate the infection.
- the infection becomes 'walled off' by fibrous (scar) tissue (a response by the body to prevent the infection from spreading further), but in doing so, it also makes it more difficult for the horse's immune system to effectively fight the bacteria, and for the drugs administered to penetrate and kill the infection.
In cases where infection intermittently 'bursts out', often preceded by a period of lameness due to the inflammation and build of pus within the foot, it is necessary to surgically debride or curette ("trim away") all of the dead and infected material. This can sometimes be done with the horse standing and sedated, but is often much more effectively accomplished with the horse anesthetized. The area can then be thoroughly investigated and more extensive surgery performed, where necessary. If infected or dead tissue is left behind this will encourage the infection to recur.
After surgery and thorough cleansing, the wound is packed with sterile gauze soaked in antiseptic solution (e.g., dilute povidone iodine) and the foot is bandaged and the horse is stabled in clean, dry conditions. The bandages are regularly changed and the wound re-dressed until it has completely healed.
In some cases it may be necessary to either remove a section of hoof wall or drill holes in the hoof to allow the infected area to drain (the collateral cartilages extend down below the level of the coronary band into the foot).
Tetanus antitoxin must be given, if the horse is not fully vaccinated up to date or if vaccination status cannot be confirmed (see our handout on Tetanus).
When completely healed, re-shoe the affected foot, gradually attempting to correct any hoof malformation.
How can quittor be prevented?
Your horses' feet should be regularly trimmed and shod to prevent hoof cracks from forming.
All puncture wounds, either nail pricks or other accidental injuries, should be treated, by cleaning them and applying an antibiotic foot spray and poulticing, where necessary, without delay.
The prognosis for complete resolution and return to soundness is poor for long-standing cases of true quittor, especially those who have developed hoof deformity. Make sure that your horses are always fully vaccinated against tetanus, an invariably fatal infection that can gain access through hoof injuries.
Edited by Kim McGurrin BSc DVM DVSc Diplomate ACVIM © Copyright 2010 Lifelearn Inc. Used and/or modified with permission under license.