Knowledge about hooves
Hufkrankheiten

Thrush in Horses

7 Min. Lesezeit

There is probably no other hoof problem in the horse world that is as widespread and as often underestimated as thrush. For many horse people, thrush is so common that they dismiss it as a natural evil one simply has to live with. So where exactly is the problem?

Why thrush is problematic

Thrush is anything but normal: the hoof is infested with horn-destroying bacteria that trigger a vicious cycle. The bacteria eat away at the frog horn, causing the frog to gradually diminish over time. However, the frog has the important job of acting as a cushion in the rear part of the hoof. On one hand, it has a shock-absorbing function, and on the other, it ensures that the bulb area of the hoof is pushed apart when the hoof strikes the ground. This is particularly important for the hoof mechanism


When the frog can no longer perform this task, the hoof becomes increasingly narrow in the rear area – a contracted hoof develops. This further constricts the (already atrophied) frog, reduces blood circulation in the hoof, and restricts the frog's growth. In addition, the frog clefts become very narrow, causing more dirt to lodge there and promoting the bacterial environment. So the situation gets progressively worse.


In advanced thrush, the bacteria can eventually eat their way down to the sensitive corium – at that point, at the latest, any contact in this area causes pain. As a horse owner, you notice this when your horse flinches in pain while you pick out the frog cleft.

Many horses then also alter their gait because they don't want to put weight on the painful area when the hoof lands. Instead of a healthy heel-first landing, many then show a toe-first landing or lameness, especially on soft ground (because the hoof sinks in more, putting more pressure on the painful frog).


Once the bacteria have finally eaten their way to the corium, the situation can once again worsen dramatically: in some cases, the irritated corium starts producing abnormal horn in a proliferative manner – this is canker.


But it doesn't have to come to this. To combat thrush effectively (or prevent it from occurring in the first place), it is important to take a closer look at the causes.

Causes of thrush

The primary culprit behind thrush is the bacterium "Fusobacterium necrophorum." This is an anaerobic bacterium (meaning it lives under low-oxygen conditions) that is part of the normal flora of many mammals (it is found, among other places, in our human oral cavity and the digestive tract of various pets). When these bacteria reach the hoof, for example via horse manure, and become trapped there without air access, they thrive and eat away at the softest horn they can find: the frog horn.


But then why don't all horses have thrush? After all, sooner or later every horse steps into a pile of manure, even in the cleanest stable.

The answer is simple: a healthy hoof is resilient and self-cleaning. When the horse moves and the frog is healthy, dirt quickly falls out of the hoof on its own. Moreover, a healthy frog is relatively hard and therefore not easily eaten away.


However, the situation looks different if the hoof already shows signs of contraction, is severely neglected, or if the frog is no longer entirely healthy. Under such conditions, the hoof is more susceptible to infections of all kinds, and manure lodges more stubbornly in the frog clefts. This is also the case if the horse permanently stands on feces-soaked ground or cannot move enough on harder surfaces.

How to effectively combat thrush

Many horse owners despair at the task of getting thrush sustainably under control. The reason is simple: usually only a product is applied to the frog, which is supposed to eliminate the thrush. But if the actual cause is not addressed, this is a fight against windmills.


To get rid of thrush in the long term, both the causes must be addressed and the acute infection must be treated. The problem has to be looked at and solved from two angles, so to speak.


Improve husbandry

First, sufficient hygiene and exercise must be provided. Your horse should be able to stand dry and clean for several hours a day and move around freely.


Depending on how bad the situation already is, the ground conditions may also need to be changed. If the frog is already severely degenerated and there is massive contraction of the bulbs or heels, a yielding layer on a firmer surface should be provided. Sand ground is ideally suited for this. On such a surface, the hoof can sink in and the (atrophied) frog can regain contact with the ground. In this way, the frog is stimulated and encouraged to grow and can once again contribute to the hoof mechanism – counteracting any existing heel or bulb contraction.

Have hooves correctly trimmed at regular intervals

Proper hoof trimming at the right intervals is an important building block in getting thrush under control. Affected horn material should be cleanly removed. The bars should be shortened to a functional length and any lever forces – including at the hoof wall – should be removed. If necessary, the alignment of the hoof also has to be corrected if the rear frog-heel area is overloaded.

Clean hooves properly and treat thrush

As the final building block, the infection itself must be addressed. In superficial cases, daily picking out and, if necessary, thorough scrubbing with a mild soap (e.g. curd soap or green soap) is sufficient.


In cases of deep-seated thrush, however, the affected areas must be treated daily with an appropriate agent. It is less important which agent is used than how it is applied. First, the infected frog cleft must be thoroughly cleaned of the decomposed material. A proven method is to wrap a rounded wooden stick with a thin, soft cloth and pull it through the frog cleft until the black, greasy layer is removed. If your horse reacts sensitively during this, you must proceed very cautiously: you may already be dealing with exposed corium, and it should absolutely not be irritated by the cleaning.



Afterwards, you can finally apply the agent of your choice. Again, the same principle applies: if the thrush is already very deep and there is a suspicion that the corium is already affected, caution is required. In these cases, only very mild agents may be used in order not to further irritate the corium. Essential oils or vinegar-based preparations, for example, are suitable for this. Colloidal silver has also proven effective in some cases.

The important thing is that the applied agent actually reaches the place where it is needed: deep in the frog cleft. It is often useful to soak a piece of gauze bandage with the chosen substance and insert it deep into the frog cleft. This tamponade should then remain in the hoof and be replaced at the latest every two to three days (or as soon as the old material has fallen out on its own).


If the thrush is still rather superficial, more strongly drying agents can also be used, such as those containing copper sulfate or zinc oxide. Toothpaste or mouthwash can also be used as a home remedy – after all, it's the same bacteria as in our mouths. However, it must be absolutely certain that the thrush has not already reached the sensitive corium.


As a last resort, a topical antibiotic can also be applied when prescribed by a veterinarian. However, it should always be borne in mind that the antibiotic ultimately ends up in the ground on which the horse stands. Especially when horses have access to pasture, careful consideration should be given to whether all other options have really been exhausted and, in particular, whether the causes have been addressed. Because only then will any other treatment of thrush be crowned with success.

Author: Nathalie Kurz www.mein-leben-ist-ein-ponyhof.at

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