Demystifying Fungal Infections of the Equine Hoof

Scientists estimate there are millions of fungal species in the world, some of which can cause a variety of diseases in humans and animals. Think ringworm and thrush. You might be aware that your horse is susceptible to fungal infections of the skin and respiratory system, but did you know fungi can also affect your horse’s hooves?

Journeyman farrier Mike Wildenstein, CJF, APF, FWCF (Hons), who was the resident farrier at Cornell University for two decades, recently spoke about fungal infections of the hoof at the 2020 Northeast Association of Equine Practitioners Symposium, held virtually.

Demystifying Fungal Infections of the Equine Hoof

Often, the first sign of a fungal infection of the hoof is a separation between the sole and the hoof wall that can be seen from the solar surface, or bottom, of the hoof, Wildenstein said. You might see visible pock marks, black dots, or striations on the sole. The horse might be lame, especially if the fungus has eroded the sole or frog.

Some fungal infections of the hoof are superficial and affect only the outer hoof wall, or stratum externum. These infections can be treated easily with topical products containing tea tree oil, eucalyptus oil, pine tar, or Venice turpentine, Wildenstein said. He advised farriers to apply a hoof dressing after shoeing, because nail holes are common locations for fungal infections.

Diagnosing and treating fungal infections of the inner structures of the hoof–the stratum medium and stratum internum–can be more difficult. These types of fungal infections are more likely to cause lameness, and your veterinarian might need to take radiographs to determine the extent of hoof wall separation.

Fungal Infection Factors

After years of researching fungal infections of the hoof, Wildenstein noticed two things common to many fungal infections: environmental factors and causative factors.

Around the world, fungi thrive in tropical climates that are hot and humid. Wildenstein, who lived in New York, noticed that horses that spent the winter in Florida were more prone to fungal infections than horses that never left New York. The same thing happened after extreme weather patterns, such as hurricanes.

Demystifying Fungal Infections of the Equine Hoof

“When a hurricane comes up the coast and hits Florida first, those wind currents will carry fungi and even small insects all the way up into New England,” Wildenstein said. “After a hurricane, if the weather is hot and humid for a period of time, these fungi will grow very rapidly, and you’ll see it in a lot of horses’ hooves. So, we get things that would not be normal for that part of the world, except in a very specific weather pattern.”

This year, the hurricanes from the Gulf of Mexico carried a host of fungal issues to the Midwest, he said. The above-average warmth in the Midwest provided tropical fungi an appropriate environment in which to thrive.

He also noticed that many horses with fungal hoof infections had other hoof issues first. Things such as laminitis, abscesses, or injuries are often causative factors for a secondary fungal infection.

“There are other diseases that can create problems to the outside of the hooves that are not necessarily fungal related, though there can be secondary fungal infections in there,” Wildenstein said. “Identify the causative factor. Is there a lesion? Did something happen to the foot? Was there an abscess track?”

Hooves that are badly broken and cracked are also more prone to developing fungal infections.

Preventing Fungal Hoof Infections

You can do certain things on a regular basis to reduce the risk of your horse getting a fungal infection of the hoof. While you can’t do much about the weather, you can manage your horse’s physical environment to prevent fungal growth.

“We found that people who got sawdust (bedding) directly from the mill, and it wasn’t kiln-dried or anything, had a greater incidence of fungal growth in their horses’ hooves,” Wildenstein said. “People who used straw and didn’t change it on a regular basis had a greater incidence of fungal activity.”

Wildenstein recommended keeping the horse’s environment clean and dry.

The best way to prevent fungal infections of the hoof is also the easiest—practice good hoof hygiene. Pick your horse’s hooves daily to remove dirt and debris, he said. Wildenstein also recommended washing the hooves occasionally with a diluted surgical scrub.

“Regular hoof care by a professional farrier is an important part of equine management,” Wildenstein said. “That’s every four weeks. But picking out the hoof should be a daily management project.”