Thrush and canker in Horses (Equis) | Vetlexicon
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Thrush and canker

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Thrush and canker

Foot problems are one of the most common causes of lameness in horses. However, the care of horse's feet is often overlooked by owners. Neglected feet can develop many conditions which, if left untreated, can result in severe lameness with loss of use of your horse. Maintaining your horse's feet in good condition is of primary importance. Thrush and canker are two conditions of the foot that owners should be aware of. Daily cleaning of your horse's feet will help identify these conditions in their early stages when treatment is often simpler and more effective.

Canker of the frog ©Beatrice Funiciello

What is thrush?

Thrush is a common bacterial/fungal infection which affects the frog and sole of the foot, producing malodorous, black necrotic material particularly in the grooves between the frog and the sole (frog sulci). If left untreated, it can affect deeper structures within the foot. It is most commonly seen in horses kept in damp conditions or through poor hygiene. However, it can occur in horses kept in a clean environment. Thrush requires treatment by your veterinarian and good management practices to ensure that feet are kept dry and in good condition.

What causes thrush?

Thrush is caused by many organisms but most commonly isolated is Fusobacterium necrophorum, an aggressive bacteria that attacks the soft tissues of the frog. Thrush is usually a result of poor hygiene, including failure to pick out the feet regularly, stabling on soiled/wet bedding and turn-out in continually damp conditions. If the hoof is constantly damp and dirty, this allows bacteria to penetrate the soft tissues and initiate an infective process.

How will I know if my horse has thrush?

If your horse has thrush you will notice a greeny-black moist substance in the grooves between the frog and sole, which has a characteristically unpleasant smell. There is usually pain when pressure is applied to the affected areas. In severe cases the bacteria may begin to eat away at the soft tissues of the frog exposing the deeper sensitive tissues; there may also be general swelling around the lower part of the leg. Hind feet are most commonly affected but it is also seen in the front feet too.

Can my horse be treated for thrush?

Yes! Firstly ensure that your horse is stabled on a nice clean dry bed and if turned out, isn't standing in wet, muddy conditions. The affected feet should be thoroughly cleaned and in advanced cases your veterinarian or farrier may need to cut away any diseased, necrotic tissue with a hoof knife. You will then need to wash the areas with an antiseptic solution on a daily basis until the diseased tissue has healed during this period you should ensure that your horse is kept in a clean and dry environment. Your veterinarian will be able to advise you regarding the best topical medication to use in each case.

How can I prevent my horse from developing thrush?

Ensure good stable management and regular foot care. Your horse should be stabled on clean dry bedding and if turned out shouldn't be allowed to constantly stand in damp conditions. Your horse should also receive regular hoof care from a registered farrier or hoof care practitioner to maintain good foot conformation and healthy frog tissues.

What is canker?

Canker is similar, but a more serious condition than thrush. Although it is rare, unlike thrush it can be difficult to solve. It is a severe bacterial/fungal infection (proliferative pododermatitis) that generally originates in the frog, and affects the heels, horn and underlying structures of the hoof. The clinical signs are the development of a foul-smelling white/grey pus in and around the frog and the presence of granulation-like tissue which often bleeds. Lameness is often variable depending upon the depth of structures involved. Canker is mainly seen in large draught horses which tend to have deep grooves (sulci) in their feet, and horses kept in wet tropical climates or on wet/soiled bedding for prolonged periods of time.

What causes canker?

Canker is caused by a Bacteriodes spp, an aggressive bacteria that attacks the deeper live tissues of the frog and heel without the need for oxygen, which means the bacteria can spread very quickly throughout the foot. This bacteria causes abnormal growth (proliferation) of the horn and tissues within the hoof capsule.

How will I know if my horse has canker?

Canker can be mistaken for thrush in its early stages. Unlike thrush though, a horse with canker will develop signs including a cheesy white pus discharging from around the frog, and the diseased horn within the hoof starts growing out from the frog which resembles a cauliflower-like growth. Horses may stamp their feet due to the discomfort and severe cases may show lameness, swollen lower limbs and even a reluctance to stand. The condition can affect both fore and hind feet.

Can my horse be treated for canker?

Canker can be very difficult to treat due to its invasive nature. If caught early, the diseased parts of the foot can be removed, and a course of antibiotics prescribed to keep the bacteria at bay and to allow new healthy tissue to form. Depending on the severity of each case, it can take a few weeks and even months for a horse to fully recover from canker. Application of a hospital plate (specialized shoe) is required for successful treatment of chronic cases often in association with antibiotic soaked swabs and systemic antibiotics.

How can I prevent my horse from developing canker?

Prevention is the name of the game. Good stable management and hygiene with daily mucking out; make sure your horse is always kept on clean dry bedding. Daily foot care and regular visits from your farrier/hoofcare practitioner is also essential. Owners of heavy breed horses should be extra vigilant in the daily checking for signs of the disease due to their inherent predisposition to the condition.