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Hoof Cancer: Early Detection and Proper Treatment
The diagnosis "equine canker" causes many horse owners great concern. The good news, however, is: if the condition is detected and treated early, the chances of recovery are very good. Yet it is precisely the early stage of canker that is often overlooked, with a diagnosis only being made once the disease has progressed. That is why with this article we want to provide some clarification so that the condition can be better recognised by horse owners and countered in time.
What is equine canker and how do you recognise it?
Equine canker is not a "real" cancer (i.e. not a carcinoma), which is why in English it is called "equine canker" (and not "cancer"). Instead, canker is a wound-healing disorder of the corium of the hoof, similar to proud flesh in skin wounds. More precisely, canker is a "chronic hypertrophic pododermatitis" – this means that the cells of the hoof corium are enlarged and abnormal keratin production (parakeratosis) takes place. The hoof horn thus "proliferates", producing the typical cauliflower-like growths on the hoof.
However, these growths already represent the advanced stage. In the beginning, canker appears rather inconspicuous – at least visually. Because what is far more noticeable is its smell: canker is accompanied by a very characteristic stench. Many people describe the smell as cheesy-pus-like-putrid – in any case very repulsive.
Another distinguishing feature is that the tissue is heavily perfused with blood and starts to bleed very quickly, even when only lightly touched (e.g. when picking out the hooves).
Typically, canker begins in the area of the frog (which is why it is also called "frog canker"), where a whitish-yellow or greyish greasy discharge is often visible.
However, canker is not exclusively limited to the frog, but spreads under airtight conditions and can thus undermine the entire sole and wall and even "blast" them off. In areas where the canker has no direct counter-pressure (for example, in the lateral sulci of the frog), threadlike villi of the corium often appear.
Often only one hoof is affected by the disease at first, but subsequently all four hooves may become involved. Statistically, hind hooves are more frequently affected than front hooves.
The condition can also spread to the coronary band (coronitis). If this is the case, the coronary band looks irritated (swollen and reddened) and typically the hairs no longer lie flat there but stand out.
Canker is usually very painful on contact, which is why many affected horses also show lameness. But even lameness often initially appears rather subtly as latent sensitivity and is therefore often overlooked as the first sign. In the advanced stage, however, many horses go very noticeably lame.
Cause(s) of canker
Although it is a very serious disease, canker is remarkably poorly researched. To this day, it has not been conclusively clarified exactly how canker develops. For a long time it was assumed that the disease was caused by bacteria or papillomaviruses, but this has since been refuted – at least as the sole cause. Rather, it is now assumed to be a multifactorial event, i.e. several factors must coincide for the disease to break out.
There are several conditions that can lead to irritation of the corium, which in turn can cause canker.
Pressure conditions in the hoof
Insufficient hoof care or unfavourable husbandry conditions can lead to bruising in the hoof, particularly in the frog region. This includes overly long bars and/or heels, as well as contracted hooves. The resulting pressure irritates the corium; if this condition persists for a long time, it can eventually turn into canker.
Some schools of hoof care even suggest that the hoof is trying to "make room for itself again" with the proliferating tissue.
Infections and thrush
The corium can also be excessively irritated by a prolonged infection. This includes in particular thrush: if it eats its way through the upper horn layers, it very quickly comes close to the corium. Canker is therefore often preceded by severe thrush. This connection is so common that many hoof care providers hold the view that canker always develops from thrush.
Even though there is probably a connection between these two hoof diseases, they differ fundamentally: while thrush is a horn-decomposing (i.e. breaking down) process, canker is a horn-forming (i.e. building up) process. Furthermore, thrush affects dead tissue (horn), whereas canker affects living tissue (corium).
Both diseases produce foul-smelling, greasy material, but as an owner you can easily distinguish between them: thrush appears deep black, whereas canker appears very light. The smell of thrush is more reminiscent of rotten eggs (because the bacteria release the sulphur contained in the hoof horn as they decompose it), whereas the smell of canker is perceived as significantly more intense and unpleasant and is described as more carious or purulent/putrid.
The transition between the two diseases can be fluid, or both can be present at the same time: for example, canker can already be spreading in the central sulcus of the frog, while the lateral sulci are "only" affected by thrush.
Nutrition
The extent to which nutrition plays a role in the development of canker is a matter of debate among experts. For instance, it is discussed whether a nutrient deficiency (particularly a zinc deficiency) can lead to degenerate horn production and therefore canker.
What is undisputed, however, is that the hoof also functions as a detoxification organ, and the corium is particularly stressed in this process. Feeding should therefore be reviewed especially if there are – or were – concurrent metabolic or skin problems (e.g. mud fever, sarcoids or eczema). Because even if these problems are perhaps not currently acute, the metabolism may still be impaired by them, or a nutrient deficit may have developed as a result.
Genetics
It is also unclear whether there is a genetic predisposition to canker. It seems that heavier breeds with a lot of feathering (draught horses, Tinkers, Friesians, etc.) are disproportionately often affected by canker. However, these very breeds are also frequently affected by metabolic problems and thrush, which is why this might be less of a genetic influencing factor and more a matter of the same triggering factors coinciding. This could also include the often-elevated nutrient requirements of these breeds (for example due to overweight or a lot of muscle mass).
Treatment options
There are various approaches to treatment, which depend on the respective stage and local conditions (stable hygiene). The diagnosis and the individual treatment plan must in any case be made by a vet, which is why we do not want to recommend any specific treatments in this article.
However, one thing is important: successful canker treatment is teamwork – between the vet, hoof care provider, feeding expert, stable operator and horse owner. A horse with canker must absolutely be kept dry and clean, which often means adjusting husbandry conditions. A nutrient balance analysis should definitely be carried out and the feeding adjusted if necessary. The hoof must be trimmed at close intervals (every 2-3 weeks) and meticulously cared for by the owner in between. In most cases, this will include daily cleaning with mild (curd) soap as well as applying a hoof bandage. The guiding principle is: the corium 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 in the early stages, treatment is admittedly labour-intensive but not difficult. In the case of missing (or too late) treatment, however, the chances of success are very low – in the worst case, the horse may even have to be euthanised.
Surgical removal of the affected tissue is also repeatedly recommended. However, such an operation is an extremely invasive (and not always successful) procedure and should therefore always only be considered as a last option once all other measures have shown no effect.
Therefore, with canker in particular: the sooner the first signs are correctly interpreted and treated, the greater the chances of a complete and uncomplicated recovery.
Author: Nathalie Kurz www.mein-leben-ist-ein-ponyhof.at
Images: Renee Hüttenbrenner, Iren Altmann, Anna Dorothea Konz
