Thrush - Is It Making Your Horse Lame?

Thrush is something that at one time or another all horse owners will likely have to deal with. It is not a product of neglectful horse care, nor is it a product of unsanitary living environment etc. Thrush is a combination of bacteria and fungus that can eat away at the frog tissue in the hoof. These bacteria and fungus are more prominent in wet conditions and thrive in moist ground, but can also be a problem in dry conditions. In the image above you will see the healthy frog on the right, the thrush infected frog on the left. You will notice that the central sulcus, the area at the rear of the frog in the middle, in the healthy hoof is just a small indent, but in the affected hoof it is a deep crack. This is the first area that thrush usually starts to affect. What happens is the the thrush eats away at the healthy tissue and creates a "home" for itself within the sulcus of the frog. The deeper the crack, the better the hiding spot for the thrush to thrive and eat more healthy tissue. It is a vicious cycle and can be extremely hard to beat once it gets to this advanced stage.

Minor surface thrush is much easier to deal with. Some ratty tags on the frog, or a small infection of the central sulcus can usually be treated with diligent hoof picking and 2-3 times a week topical treatments with Artimud and/or HoofStuff. More severe thrush can take weeks or even months to clear up and can require soaking, booting and even diet/nutrition changes. 

So why is thrush an issue? At the start with a minor case, thrush doesn't really alter the horse in any way. If we catch it early enough and treat it then it is a non issue. If thrush persists and manages to eat into the frog tissue deeper it can cause the horse to feel some sensitivity when loading the back of their hoof and can cause them to land flat or toe first as opposed to heel first as they are intended to land. Horses land heel first in order to use the frog and its underlying structure, the digital cushion, to absorb impact and dissipate energy vibrations. When the horse alters its movement and doesn't land heel first that impact energy travels up the leg into the joints, shoulders/hip and back and causes excess strain on the body. This can create a cascade effect that can significantly affect the performance of the horse and in serious cases can even lead to lameness.

When the thrush eats through the frog and into the sensitive digital cushion it is extremely painful for the horse. The hoof and its outside structures are designed to protect, and are insensitive structures, meaning they do not have nerves and blood supply directly within them. The nerve receptors and blood supply are located within the sensitive structures: the digital cushion, solar corium and lamina. So this means that a minor surface infection of the frog really won't cause much pain, however once the thrush eats into the digital cushion it is in fact an open wound of the horse, and is painful when impacting the ground. The horse then alters their movement to avoid loading the frog as much as possible. This is an issue because of the previously mentioned strain on the body, but also because healthy frog tissue is generated because of positive impact forces, and without the horse loading the frog it won't receive these forces. This creates a long term problem as the frog and digital cushion will atrophy over time due to lack of stimulation and will alter the shape of the hoof capsule. You then have a significant reduction of impact energy dissipation and a horse that is absorbing that impact in their joints, therefore more prone to develop arthritis and other joint related conditions.

The pictures below show you the severity of a thrush infection once it gets into the digital cushion. These cadavers have the outside structures removed and the one on the left has an infection so deep that a hoof pick can be inserted into the crack approx 1/2 an inch. This is a deep open wound for the horse and extremely painful. The cadaver on the right shows a healthy digital cushion with a normal central sulcus without infection.

Photo credit to Kate Simmer, via Facebook

So what can we do about it? For minor infections treating topically is easy. Your local tack store will have several products available that are designed to kill the harmful bacteria and fungus that cause thrush. ​My personal word of of caution would be to read the ingredients label on those products. What you want is something that will kill the harmful bacteria and fungus, but not the healthy tissue. A lot of commercially made thrush products have ingredients like formaldehyde, formalin, turpentine etc. These substances are toxic to healthy tissues and will indeed kill the thrush but also the regenerating frog tissue. My favorite thrush products are made by Red Horse and are Artimud and HoofStuff.

Think about a deep thrush infection like an open wound on your own skin. Use products that will keep it clean but also encourage healthy growth. Products such as antibacterial wound scrubs used in human medicine, as well as barrier creams and ointments. My personal method for treating for this type of infection is as follows:

• Thoroughly clean the hoof - I use Sole Cleanse to get into and around the crevices in the frog (be careful with a deep infection, it will hurt your horse to scrub inside there, instead use a syringe to flush the area with your cleaning solution). You can also soak in products such as White Lightning or Cleantrax. 

   

• Dry the hoof and apply HoofStuff in the central sulcus of the frog very gently with your hoof pick. Then apply Artimud to the entire frog and collateral grooves. Remember less is more, you do not need to overfill the grooves.

 

• Prepare your hoof boot of choice. Boots will help to keep the frog clean and dry and make sure your horse can't stand with their feet in their urine or manure which will further exasperate the infection. I use my Cavallo Trek boots, with a 1/2 inch thick felt pad inside, topped with GoldBond Medicated Foot Powder. Put the clean and dry hoof, coated in the zinc oxide cream into the boot. Note: to make felt boot pads I buy a 1/2 inch thick felt saddle pad for approx $40 and cut several boot pads out of this pad. It is far more economical then buying individual boot pads and they are machine washable and can be used a few times before they wear out. 

 

• Repeat this process every second day. Continue this regimen until the infection has closed and the frog is sufficiently regenerated. For some horses long term boots can rub or irritate their heel bulbs or pasterns. Make sure you have the right fit of boot and style that can accommodate a felt pad, and I also use the Cavallo Pastern Wraps when needed.

Here you can see my horse wearing a very well used Cavallo Trek boot, packed with the felt pad and Gold Bond foot powder. These Treks are 3 years old and still work great as rehab and riding boots!

Easyboot Cloud therapy boots are also a great rehab boot. I sometimes use these if I need more protection for the hoof and a thicker padding. These are not suitable for riding so it makes them strictly a turnout/therapy boot. If you are looking for Cloud boots contact me as I can special order them.