Thrush is an affliction that is found on the underside of a horses hoof and can affect the sole, cleft and frog. Thrush can be caused from fungus or bacteria that develops in damp airless areas of the hoof that are most often packed with manure, dirt and other debris. This affliction can be harmless in the early stages, but if it is left untreated, it will cause damage to the hoof and even lameness.
What causes thrush?
Its not yet clear whether a type of fungus or bacteria causes this affliction, but most professionals agree that the organism lives in the soil. There is also a theory that the organism responsible for thrush already exists in the horse itself, thriving in the poorly oxygenated areas like the clefts of the hooves. This may not be noticeable in dry weather, but when there is an increase of moisture in the air, then an infection could make itself known.
What are the signs of thrush?
When you are cleaning out the hooves, if you notice a moist, black, foul smelling substance, this is the first sign that thrush is hiding in the cleft. The foul smell is unmistakable and once you smell it for the first time, you will remember that distinct odor. You will be able to scrape out all of the black substance, but there will be a dark stain left behind.
How is the horse affected?
A small amount of thrush can be harmless and even very treatable when caught in the early stages. The most obvious signs are a black tarry substance and a foul smell. If thrush is left untreated, it can spread and damage the hoof and permanently lame the horse.
Can thrush be avoided?
Cleaning the hooves on a regular basis to remove all the debris will allow fresh air to the affected areas, along with keeping the foot dry. Trim the hoof on a regular basis to prevent deep clefts, where the thrush organisms can hide. Most importantly, keep all the areas of your horses environment clean and dry. Remove all manure, soiled bedding or spoiled food and any other damp places that are inviting to bacteria and other organisms.
Source: Dog and Horse Care