Injuries & Diseases of the Hoof IV: Canker, Thrush and Quittor
Conditions of the frog and adjacent structures, such as canker and thrush, are predominantly seen in horses kept under unhygienic wet conditions.
Clinical signs and diagnosis of Canker
Canker or hypertrophic pododermatitis of the frog and adjacent structures is seen predominantly in draught horses kept under unhygienic wet conditions. Signs include abnormal finger-like papillae of hypertrophic (enlarged) horn growing from the frog and adjacent sole that bleeds easily. It can reach considerable proportions and become infected and exudative (oozing). Early lesions are often not painful and lameness may only occur in later stages.
Diagnosis is confirmed by clinical appearance and characteristic histology showing chronic pododermatitis.
Treatment of Canker
Surgical removal of all affected tissue is essential
Soaking and poulticing of the foot in a povidone-iodine soapy solution for 2-3 days before surgery is helpful
Surgical debridement should continue until healthy tissue is exposed over the whole area
After surgery the area should then be dressed with astringent or metacresosulphonic acid
Once the initial bleeding and exudation have been controlled, the area is kept dry using antibiotic powders or spirit-based aerosols
Metronidazole mixtures in paste or cream form may also have a significant benefit
Treatment is over many months arid requires further debridement to control chronic hypertrophic growth. Benzoyl peroxide (2%) has been successfully used as a dressing, but the major requirement is to keep the horse’s feet clean and dry with daily dressings.
Thrush
Thrush is a degenerative, exudative dermatitis of the central and collateral sulci of the frog characterised by a granular black discharge and a characteristic foul smell. Local factors, such as deep cleft with narrow and occluding margins and general lack of foot care, such as stabling of horses in wet, unhygienic conditions, are significant factors in the cause of thrush.
Infection with a variety of microorganisms including Fusobacterium necrophorus is commonly present.
Clinical signs and diagnosis of Thrush
Foul smelling, necrotic black discharge from the sulci of the frog
Sometimes it is only detectable when a hoof pick or fine hoof knife is used deep in the clefts
There maybe local or more extensive undermining of the sulci of the frog and in severe cases sepsis of the deeper structures of the foot
Swelling of leg and lameness occurs in some horses.
Diagnosis is confirmed by the typical appearance and features described above.
Treatment of Thrush
Debride all necrotic frog and under run infected areas
Treat sparingly every day with 5% formalin solution worked into the cleft of the frog with a thin paintbrush – this should only be used under the direction of a veterinary surgeon
Use of plain and contrast radiography determines if infection has cleared
Metronidazole paste applied twice daily for up to 3 weeks is often effective.
Lateral cartilage necrosis (Quittor)
Quittor describes lameness associated with swelling and intermittent or persistent purulent discharge from a sinus tract over the area of the lateral cartilage, usually associated with trauma and subsequent infection, inflammation and necrosis of the lateral cartilage.
Clinical signs and diagnosis of Quittor
Lameness may or may not be obvious
In the early stages a painful swelling over the area of the lateral cartilage develops
A persistent or intermittent, usually scanty, purulent discharge develops almost always above the coronary band
Periods of apparent healing are followed by repeated, though seldom increasingly severe, discharge
Local pain is not often marked during periods of discharge
In some cases, the extent of the discharge can be minimal and show as a slight matting of the hair over the site
Diagnosis is confirmed by a history of injury to the coronary band over the lateral cartilage, characteristic clinical signs and discharge above the coronary band
Using a catheter and contrast medium or a sterile blunt probe placed in the tract will assist in assessing the extent of the problem and differentiate it from other causes of discharging coronary band sinus tracts, such as ‘seedy toe’, white line disease, laminitis and solar sepsis.
Treatment of Quittor
Surgical removal under general anaesthesia is essential to completely remove all damaged cartilage
Early lesions treated aggressively carry a good prognosis
While the outlook for extensive old lesions, especially when they involve the coronary band or coffin joint capsule, is much worse
Lameness often persists after surgery in the latter cases
Unilateral digital neurectomy can be considered as a palliative treatment if the surgical wound has healed satisfactorily.
By Dr Reginald R. R. Pascoe AM - Last updated 16 November 2012
