Thrush is a common hoof infection that is not defined solely by the organism responsible for the disease; rather, it is diagnosed by the typical appearance and symptoms of the affected hoof anatomy. Horses kept in wet or unsanitary conditions for prolonged periods of time are susceptible to Thrush, but those kept in pristine conditions can also develop this infection. It may occur when the hoof’s natural self-cleaning ability is compromised by excessive confinement, inappropriate farriery, chronic lameness, or nutritional deficit. In any case, treatment should begin swiftly to avoid complicated cases that can lead to permanent lameness. Thrush is common, and every horse owner should be aware of how to treat it – preferably, how to prevent it from occurring.
Thrush affects the frog (the triangular soft area on the underside of the hoof) and the sulci (the grooves that surround and transect the frog). Horses with deep sulci or abnormally shaped hoofs may be more susceptible. These structures will contain black, pasty, foul smelling, necrotic material when examined and cleaned. Anaerobic bacteria and fungi are commonly cultured from Thrush infections and are considered opportunistic pathogens. The type of organism identified rarely alters the treatment protocol except possibly in very advanced and resistant cases. In the early stages, horses are not lame from Thrush, although the disease may be a complication of other causes of lameness. As the infection invades the deeper structures of the foot, the condition will certainly become painful.
Horses kept in damp conditions, and those denied regular exercise, are most likely to develop Thrush. Any condition which interrupts the normal flexion of the foot, and thus the regular decontamination and oxygenation of the hoof, may also lead to this condition however. Poor diet may be another contributing factor. The idea that Thrush occurs only in unsanitary conditions has long been disproven.
Mild cases of uncomplicated Thrush can be treated by the horse owner. Advanced cases, and those situations where the condition is secondary to another cause of lameness, warrant the consultation of a veterinarian. The affected hoof must first be debrided of all necrotic and infected tissue. A farrier may be helpful in this effort. The horse should be removed from damp, confined conditions and allowed to exercise normally. Stimulating hoof flexion through natural movement will help to increase blood supply to the frog, decrease the accumulation of debris, and oxygenate the wound. If there is an anatomical defect of the hoof, the expertise of a veterinarian and farrier will help to identify and correct the problem and prevent recurrence.
The hoof will need daily cleaning and medicating in the treatment of Thrush. This is best done with an ample supply of fresh water and a stiff-bristle brush. Antiseptic soap like betadine or chlorhexadine is recommended. The hoof should be rinsed well and thoroughly dried after cleaning. It will require a clean work space to accomplish this. After the hoof is blotted and air-dried, a number of topical Thrush remedies are available that can then be applied to reduce bacterial colonization and improve healing. Applying these medications to a hoof that remains impacted with necrotic material will not be effective.
When treated promptly and aggressively, mild Thrush responds well and a full recovery is expected. If there are underlying causes left unresolved, healing will be prolonged, and re-infection is likely. Progressive cases will require veterinary care and carry a more guarded prognosis.
Prevention involves routine inspection of the hooves along with proper trimming as needed. The horse should not be kept confined more than necessary, and stables should be kept clean and dry. Hoof picks and brushes can be used to remove accumulated debris, but if the debris is persistent, a farrier or veterinarian may be needed to assess the anatomy and health of the foot.