Thrush is an infection of the horses frog resulting from poor foot hygiene and prolonged exposure to wet conditions These infections most often involve the bacteria Fusobacterium necrophorum and occur in the central and lateral sulcus (clefts or grooves) of the frog.. Thrush appears as a black, foul smelling discharge from the central or lateral sulci of the frog. Affecting either hind or front feet, deep narrow clefts predispose to thrush more than normal. Discharge from the affected area is variable and may not be noticed unless the sulcus is closely examined and cleaned out. In more advanced cases the frog and sole tissue can become under-mined or under-run. Infection of the deeper more sensitive tissues and exposure of sensitive corium can cause lameness and may lead to a secondary cellulitis and swelling of the lower limb.
Often horses with contracted heels and atrophied or weak and narrow frogs are more susceptible due to the depth of the sulci and similarly, horses with overgrown hooves are more prone to the problem.
Prevention is better than cure and thrush can be prevented with good stable management, cleaning and inspection of your horse’s frog. Additionally, providing clean, dry bedding for horses is vital, as horses that live in a wet, muddy or dirty environment are more susceptible to infection. Exercise helps to maintain healthy blood flow to all regions of the foot and helps to maintain a healthy frog with normal hoof architecture. One of the most important and basic steps to take to prevent this is to pick your horse’s feet out at least twice a day.
Treatment of early, mild cases involves debridement of affected tissue and sometimes topical treatment with iodine or hydrogen peroxide. Affected horses should be kept on a clean dry bed. More serious cases may require a more extensive debridement, antibiotic therapy and therapeutic shoeing that protects the affected area whilst it heals.
Mud fever, also known as pastern dermatitis, is another aliment arising from wet weather conditions. It is caused by a combination of different factors including skin irritation, bacteria, and moisture. The equine skin has a normal balance of bacteria on the surface however if the skin is wet for prolong periods of time the skin softens and the bacterial population change and become unbalanced, these then multiply in the damp warm environment and can lead to infection and mud fever.
Factors predisposing to mud fever include: long periods of damp and standing in wet environments, washing and scrubbing legs that causes abrasions and if not dried properly leads to a damp environment, feathers and cob types as these are harder to dry properly and also may have chorioptic mites that will break the skin allowing bacteria to enter.
Prevention (which is better) and treatment is based on keeping the skin dry and clean. If a horse does have or is prone to mud fever, it may require stabling until the horse can recover and maintain a healthy skin surface. Gentle cleaning with chlorhexidine, iodine or medicated shampoos can help re-establish a healthy population of normal skin bacteria, but you must rinse and dry them properly afterwards. Over washing or vigorous scrubbing will traumatise the skin surface and can lead to mud fever, so be conservative. If your horse has a scab, do not pick them unless they are soft and ready to fall off, picking scabs breaks the skin barrier and allows the bacteria to enter the skin again. There are many topical treatments that soften scabs whilst bathing the skin in anti inflammatories. If keeping your horse in a dry stable is not feasible then you can apply a barrier cream to the leg, these creams are designed to repel the water away, keeping the leg dry. Bandaging is also an effective way of keeping the leg dry but you must ensure the bandages do not get wet on the inside and do not rub. Sand schools or sandy soils are particularly abrasive to the skin so washing legs after exercise or turn out is important but be gentle! Proper pasture management to avoid mud pits will also help prevent mud fever.
Sometimes a mud fever infection can lead to cellulitis, when the leg swells and the swelling travels up the leg or a hot painful pitting oedema develops, it is likely your horse has cellulitis. Cellulitis will require veterinary care as horses should be assed and possibly prescribed anti-inflammatories and antibiotics to help your horse fight the infection.
Dr. C. Baldwin, BVetMed, MRCVS