Many horse owners get scared and anxious when they are diagnosed with hoof cancer. But the good news is: if the disease is discovered and treated early, the chances of recovery are very good. However, it is precisely the early stages of hoof cancer that is often overlooked and a diagnosis is only made at an advanced stage. That's why we want to use this article to do a bit of educational work so that horse owners can recognize the disease better and take countermeasures in good time.
What is hoof canker and how do you recognize it?
Hoof cancer is not a “true” cancer (i.e. not a carcinoma), which is why the disease is also called “equine canker” (rather than “cancer”) in English. Instead, hoof canker is a wound healing disorder of the hoof corium, similar to wild meat in skin wounds. More specifically, hoof canker is “chronic hypertrophic pododermatitis” – this means that the cells of the hoof corium are enlarged and there is abnormal keratin production (parakeratosis). The hoof horn "grows" so that the typical, cauliflower-like outgrowths form on the hoof.
However, these growths already represent the advanced stage. At the beginning, the hoof canker is rather inconspicuous - at least visually. Because what is much more noticeable is its smell: hoof cancer is accompanied by a very characteristic stench. Many people describe the smell as cheesy-pus-decomposing - very repulsive in any case.
Another distinguishing feature is that the tissue is heavily supplied with blood and begins to bleed very quickly, even if it is only touched very lightly (e.g. when picking out the hooves).
Typically, hoof canker begins in the area of the frog (therefore also called "ray canker"), where a white-yellowish or greyish greasy discharge is often visible.
Hoof canker is not limited to the frog, but spreads in the absence of air and can thus infiltrate the entire sole and wall and even "blast" them off. In areas where the canker has no direct counter-pressure (e.g. in the lateral collateral grooves), filamentous villi of the hoof corium are often visible.
Often only one hoof is initially affected by the disease, but subsequently all four hooves can be affected. Statistically speaking, hind hooves are affected more often than front hooves.
The disease can also spread to the coronet (collar ligament inflammation). When this is the case, the coronet looks irritated (swollen and red) and typically the hair there is no longer flat but stands up.
Hoof cancer is usually very painful when touched, which is why many affected horses also show lameness. But lameness is often more subtle than latent sensitivity at first and is therefore often overlooked as the first sign. In an advanced stage, however, many horses become very clearly lame.
Cause(s) of hoof canker
Although it is a very serious condition, hoof cancer is surprisingly poorly understood. To this day, it is not completely clear how hoof cancer develops. For a long time it was assumed that the disease was caused by bacteria or papillomaviruses, but this has now been refuted - at least as the sole cause. Rather, it is now assumed that it is a multifactorial process, i.e. several factors must come together for the disease to break out.
There are several circumstances that can lead to irritation of the corium of the hoof, which in turn can cause hoof canker
Pressure conditions in the hoof
A lack of hoof trimming or unfavorable keeping conditions can lead to bruising in the hoof, especially in the frog region. These include overly long bars and/or heels as well as forced hooves. The resulting pressure irritates the dermis; if this condition persists, it can eventually progress to hoof canker.
Some hoof trimming schools even say that the hoof wants to "make room" again with the proliferating tissue.
Infections and thrush
The hoof corium can also become overly irritated by prolonged infection. This includes thrush in particular: if this eats through the upper horny layers, it very quickly gets close to the dermis. It is not uncommon for hoof canker to be preceded by severe thrush. This association is so common that many farriers are of the opinion that hoof canker always results from thrush.
Even if there is probably a connection between these two hoof diseases, they differ fundamentally: while thrush is a horn-decomposing (i.e. degrading) process, hoof canker is a horn-forming (i.e. building up) process ) process. Furthermore, thrush affects dead tissue (horn), whereas hoof canker affects living tissue (sclera).
Both diseases produce smelly, greasy material, which you as the owner can easily distinguish: thrush appears jet black, while hoof canker is very bright. The smell of thrush is more reminiscent of rotten eggs (because the bacteria break down the hoof horn release the sulfur it contains), whereas the smell of hoof canker is perceived as much more intense and unpleasant and is described as carious or purulent/decomposing.
The transition between the two diseases can be fluid, or both can be present at the same time: for example, hoof canker can already spread in the central sulcus, while the lateral sulcus is “only” affected by thrush.
To what extent diet plays a role in the development of hoof canker is controversial among experts. For example, it is being discussed whether a nutrient deficiency (especially a zinc deficiency) can lead to degenerated horn production and therefore hoof cancer.
What is undisputed, however, is that the hoof also functions as a detoxification organ and that the corium of the hoof is particularly stressed. Feeding should therefore be checked particularly if there are – or were – metabolic or skin problems (e.g. mallenders, sarcoids or eczema) at the same time! Because even if these problems are not acute at the moment, the metabolism can still be affected or a nutrient deficit can have arisen as a result.
It is also unclear whether there is a genetic predisposition to hoof cancer. Because it seems as if heavier breeds with a lot of feathers (draft horses, tinkers, Friesians, etc.) are affected by hoof canker too often. However, it is precisely these breeds that are also often affected by metabolic problems and thrush, which is why it may not be a genetic factor but rather a combination of the same triggering factors. This could also include the increased nutritional requirements that are often found in these breeds (e.g. due to being overweight or having a lot of muscle mass).
There are different approaches to treatment, depending on the stage and the local conditions (barn hygiene). The diagnosis and the individual treatment plan must be made by a veterinarian, which is why we do not want to recommend any specific treatments in this article .
But it is important: successful hoof cancer treatment is teamwork - between veterinarian, hoof trimmer, feeding experts, stable operator and horse owner. A hoof crayfish horse must stand dry and clean, which often means an adjustment of the housing conditions. A nutrient balance should be carried out and the feeding adjusted if necessary. The hoof needs to be worked on frequently (every 2-3 weeks) and meticulously cared for by the owner in between. In most cases, this will include daily cleaning with mild (core) soap and the application of a hoof bandage. The basic principle is: the dermis should not be additionally irritated during the procedure in order to avoid an excessive reaction (horn production). Instead, bacteria should be gently eliminated and skin regeneration stimulated with mild agents.
If the disease is diagnosed at an early stage, treatment is expensive but not difficult. If there is no (or too late) treatment, however, the chances of success are very low - in the worst case the horse even has to be euthanized.
Surgical removal of the affected tissue is repeatedly recommended. However, such an operation is an extremely invasive (and not always successful) procedure and should therefore only be considered as a last option when all other measures have failed.
Therefore, when it comes to hoof cancer, the following applies in particular: the sooner the first signs are correctly interpreted and treated, the greater the chances of a complete and uncomplicated cure.
Author: Nathalie Kurz www.mein-leben-ist-ein-ponyhof.at