The Thoughtful Horseman: Treating Fungal & Bacterial Infections in the Hoof

Some studies indicate as many as 90% of our domestic horses suffer from some degree of bacterial/fungal hoof infection related to thrush. And it's not just a cosmetic issue, or a nuisance...it is excruciatingly painful...painful enough to make the horse toe-walk to avoid weighting the tender, infected heel. Painful enough and so easily ignored that it may very well be one of the leading causes of heel pain.

A combination of factors make our domestic horses so susceptible to thrush and white line disease. Lack of movement, standing in manure or urine, soft or damp footing, improper trimming, and a diet high in sugars and carbs all contribute to the problem. I cannot stress enough the ultimate importance of addressing all of these issues, and changing our typical horsekeeping situation once and for all. But aggressively and diligently treating the problem to keep the hoof clean works in a less than optimum environment.

Thrush is an infection of the central and lateral sulci (clefts) of the frog of the horse’s foot. Although the name "Thrush" implies a fungal infection, what we call thrush in a horse's frog most often involves bacteria. One species of bacterium (Fusobacterium necrophorum) is particularly aggressive, invading and destroying the frog, sometimes exposing the deeper sensitive tissues.

If you see a deep crease between the heel bulbs, with or without heel contraction, odor, or visible signs of thrush, start treating for infection. Essentially, if you can pack a cotton ball into the central sulcus (the groove at the very center of the frog that can travel up between the heel bulbs), you need to take action against infection. You probably have seen more hooves with this type of pathology than you have seen hooves with healthy frogs.

These and other pathogens can also attack the white line (laminae) and hoof wall. Commonly called white line disease or seedy toe, this is a very serious condition and should be treated immediately.

No matter what type of product you decide to use to tackle thrush and white line disease, cleaning the hoof properly first is essential.

Scrubbing with Bristle Brush and Liquid Dish Soap

One of the simplest, cheapest, and most effective ways to eradicate thrush and keep the frog healthy is hoof scrubbing using liquid dish soap. Any brand will do, and I have not found anti-bacterial soaps to be any more effective than good ol' original Dawn dish soap. Even if you plan to soak the hoof in chlorine dioxide solution, or treat with essential oils, the hoof should be thoroughly scrubbed first.

A bristle brush with a soap holding handle makes this process easy. You can do this in the washrack, or just fill a bucket with fresh, clean water and use a measuring cup for rinsing.

Far Left, hoof scrubbing tools: a bucket, a sturdy hoof pick, measuring cup for rinsing, soap filled scrub brush.
Center, using the measuring cup to rinse the hoof with clean water.
Far Right, scrubbing with bristle brush and liquid dish soap.

First, use your hoofpick to remove as much debris as you possibly can. Don't be shy about this, but be careful -- a horse with thrush may find it uncomfortable. Don't neglect dirt accumulated in the white line.

Now rinse the bottom of the foot thoroughly. At this point, you'll probably notice some dirt, pebbles, and manure that you've missed with your pick; use the pick again, and remove what you can. Rinse again. Now pick up your brush, dispense some soap, and start scrubbing. Rinse and scrub repeatedly, until the suds are clean and white. Rinse again, and make sure there's nothing more hiding down in the grooves that run along the sides of the frog, or in the central sulcus that runs up between the heel bulbs. The white line should be thoroughly cleaned as well. Once you're satisfied that the foot is clean enough to eat your lunch off of (I'm only sort of kidding here), make sure you've rinsed all of the soap off of the foot and anywhere else it might have gotten, and move on to the next hoof.

Protecting the Frog with Zinc Oxide

After hoof scrubbing, coating the frog, collateral grooves and central sulcus with 40% zinc oxide ointment (diaper ointment like Desitin) provides an effective protective barrier. Allow the hoof to dry for a minute after scrubbing before applying the zinc oxide. The ointment can also be applied into white line separation to discourage the abrasive action of sand or gravel from wearing the white line away.

Scrubbing the hoof and reapplying zinc oxide every 2 to 3 days seems to be sufficient in most cases

Coating the frog, central sulcus, and collateral grooves with zinc oxide for protection.

Using Essential Oils to Combat Deep Central Sulcus Thrush

If the central sulcus of the frog is a deep crease that runs up between the heel bulbs, using essential oils will quickly help open the area and clear up the infection. After scrubbing the hoof, use your hoofpick to pack a cotton ball or some clean gauze into the crease, and then saturate the cotton ball with essential oils. Scientific data on the topic shows very promising antibacterial and antifungal action for ALL of the following essential oils:

rosemary ♦ eucalyptus ♦ tea tree ♦ lavendar ♦ cinnamon ♦ clove ♦ lime

Lavendar, eucalyptus, and tea tree are the three I have personally had success with. Again, treatment every 2 - 3 days is probably adequate.

Coating the frog, central sulcus, and collateral grooves with zinc oxide for protection.

Chlorine Dioxide Soaking

For white line infection, or really advanced cases of thrush, soak with a chlorine dioxide solution. Once again, scrubbing the foot prior to soaking greatly increases the effectiveness of the treatment. Several companies market products that can be activated to produce chlorine dioxide. Oxine AH and White Lightening are my two favorites.

Oxine AH (Chlorine Dioxide active ingredient)

Oxine AH is a broad spectrum anti-microbial/disinfectant. It is often used in the livestock industry. The active ingredient in Oxine is chlorine dioxide; it is similar to bleach, but non-necrotizing (does not kill living tissue).

You can buy the Oxine AH and citric acid to activate HERE.

To soak all four feet of two horses:

Combine 1/2 gallon of water, 3 oz of Oxine, and 1/2 tsp of citric acid in a plastic or glass container only; it is quite reactive with metal (rusts like crazy on contact!) Soak hooves for 20 to 30 minutes. On stubborn frog infections, a weekly soak helps get ahead of the problem. I soak my own horses once a month even if I do not see signs of thrush.

Once activated, the solution is viable for about 24 hours.

It's important to contain the gases for the most effective soaking. I use empty IV bags, secured around the pastern with vet wrap or duct tape, leaving just enough slack to pour the liquid in after taping. Large Ziplock bags work, but you will need to double bag each foot and keep the horse still on soft ground, or they rip too easily. Some folks use disposable diapers wrapped around the hoof. Soaker boots or buckets are less desirable, because they do not contain the gases, and also because the horse can too easily splash the solution out of the boot.

Use enough solution to submerge the frog and collateral grooves without covering the hairline. It won't hurt the skin if you do cover the hairline, but the solution may bleach the hair a little! It also bleaches fabric, so be careful not to splash yourself, or wear old clothes.

White Lightening Liquid (Chlorine Dioxide active ingredient)

Like Oxine AH, White Lightening is a broad spectrum anti-microbial/disinfectant. The active ingredient in White Lightening is chlorine dioxide; it is similar to bleach, but non-necrotizing (does not kill living tissue). White Lightening is more expensive than Oxine, but seems to create a more aggressive solution.

You can buy White Lightening Liquid HERE. They sell a gel form, also, but I have not found the gel to be adequately effective.

To soak all four feet of two horses:

1/2 gallon of water, 3 oz. of White Lightening liquid, and 3 oz. white vinegar in a plastic or glass container only; it is quite reactive with metal (rusts like crazy on contact!) Soak hooves for 45 minutes. For serious frog infection or White Line disease, soak two days in a row every week for a month. If infection persists, continue treatment. Be watchful for sensitivity/irritation; if irritation occurs, reduce soaking frequency, and rinse hooves thoroughly with fresh water after treatment.