by Bessie Crawford
What is thrush?
Thrush is an affliction that can be found on the underside of a horse's hoof and can affect the soles, clefts and the frogs. The cause of thrush could be a fungus or bacteria that can develop in the 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's left untreated, it will cause damage to the hoof and even lameness.
What causes thrush?
It's not yet clear whether a type of fungus or bacteria causes this affliction, but most professionals agree that the organism endures in the soil. There is also the 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?
Sitting in that dusky wilderness, under that dark mountain, by the bright river which was full of reflected light, still I heard the wood thrush sing, as if no higher civilization could be attained. By this time the night was upon us.
—Henry David Thoreau (1817–1862)
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 it 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 drier. 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 horse's 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.
What is the cure?
The morning was a bright one, and perfectly still and serene, the lake as smooth as glass, we making the only ripple as we paddled into it. The dark mountains about it were seen through a glaucous mist, and the brilliant white stems of canoe birches mingled with the other woods around it. The wood thrush sang on the distant shore, and the laugh of some loons, sporting in a concealed western bay, as if inspired by the morning, came distinct over the lake to us, and, what was more remarkable, the echo which ran round the lake was much louder than the original note; probably because, the loon being in a regularly curving bay under the mountain, we were exactly in the focus of many echoes, the sound being reflected like light from a concave mirror.
—Henry David Thoreau (1817–1862)
If you discover that your horse has thrush in the early stages, then thrush will be fairly easy to clear up. There are several different products on the shelves of pet and tack stores that can be very affective, but the simpler, least expensive and very effective treatment would be either betadine or iodine.
When beginning treatment, first make sure that all areas of the horse's environment are clean and dry. Too much moisture in the environment can cause thrush to remain in the area, thus causing more problems. Next, you will need to clean out the debris from the hooves with a hoof pick. Be sure to clean the deep areas of the cleft very carefully and thoroughly and then scrub the areas with a stiff brush, being careful of the frog and heel, to get it as clean as possible.
Now apply the betadine or iodine solution generously on the bottom of the hooves, making sure that the solution penetrates every surface and crevice. Repeat this process for a minimum of five days. When the thrush is gone, continue to maintain the dryness and cleanliness of the horse's environment to keep this uninvited organism at bay.
There are other traditional cures like hydrogen peroxide, chlorine bleach, or copper napthennate that may be effective against thrush but these can also stain or burn the healthy skin and foot tissue, along with hair and clothing. These harsh chemicals are not really necessary and would not be recommended by seasoned horse owners.
What if home treatment doesn't work?
If you followed all directions and the home care doesn't get rid of the thrush with a week, then you need to call a veterinarian. If the thrush has advanced to the point of hoof damage, causing the horse to be lame, then the horse will need to be seen by a veterinarian and may even need the services of an experienced farrier.