The most common question about canker is: what is it?
The answer to that is, despite what you may read, no one really knows. When I was in college, studying equine science, I was taught that it was a type of cancer. These days, many researchers believe it is a type of bacterial infection that triggers out-of-control growth. The problem with this theory is that it does not respond to antibiotics and canker can't be reproduced even when the suspected bacteria are injected into a foot.
There is also an environmental component, although it is not hygiene (despite that often being cited, canker occurs in the most immaculate settings as well as dirty ones). I had never heard of canker occurring in donkeys, but clearly it does. Canker can occur in any horse, of any size, but it most often occurs in draft horses and is seen most frequently in the southeast US. Because of this, it seems there has to be some kind of environmental factor, but no one knows what that is. Ben did spend time in North Carolina before coming to New York, for what that is worth.
Fiona asked if canker is related to sarcoids and there is some evidence to support that, but again, no one yet knows. There is speculation that both sarcoids and canker may be triggered by bovine papiloma virus. There is an interesting article about the correlation between sarcoids, canker and BPV that can be found here along with a discussion about using chemotherapy to treat canker. It has shown some success.
When I ever bother to think about canker (which was very rare up until Ben entered my life) I take a more practical view of the problem: if it looks like cancer, acts like cancer and has to be treated like cancer, maybe we should just call it cancer until someone figures out what the hell it really is.
The reality is that canker is a rare, mysterious, bizarre hoof disease that has semi-randomly plagued horses (and donkeys) for centuries and will likely continue to do.
The next question everyone asks is: how do you treat it?
That too is a topic of great debate. Fortunately, despite not knowing exactly what it is, there has been some progress on this front. Canker often used to be a death sentence. Canker still has a guarded prognosis, but the success rate for treating it is now about 70%. What it really comes down to for successful treatment, is that the canker has to be gotten rid of entirely. How that is done is (of course) a matter of controversy.
Just about every chemical you can imagine (and some I'm sure you haven't) has been used to try to treat canker. Sometimes they work. However, the miracle cure for one horse often has no effect whatsoever on another, making topical treatments a frustrating matter of guess work, anecdotal stories and hope.
The treatment that has the most consistent and highest success rate so far, is radical excision of the canker followed by topical treatment. The most important aspect is to make sure that all of the canker has been removed with a clear margin all around it - just like cutting out a tumor.
There are various protocols for this as well. The one with the highest documented success rate involves excision followed by cryo or laser therapy to kill any missed cells. That is then followed by daily topical application of a drug (metronidazole) that is both an antibiotic and anti-protozoal combined with benzoyl peroxide (the acne medicine) mixed in acetone. It is a bizarre combination that certainly covers all the bases. It is hard to imagine a bacteria, fungus or protozoa that would survive this combined onslaught. The full protocol can be found at:
Like cancer, early detection greatly increases the likelihood of successful treatment. Unfortunately, canker often hides under healthy seeming tissue and is usually only discovered when the animal shows lameness. By the time this happens, the canker has grown large enough to invade the inner structures of the hoof. Even if successfully excised and treated, it may have caused too much damage for the animal to recover.
Maybe it is fate, destiny, luck or a guardian angel that brought Ben to the home of a true hoof nerd because I did catch it fairly early. Hopefully, it will make a difference.
On first acquaintance, Ben's foot looked very normal with the exception of a small, narrow crevice in the center of the frog. It looked exactly like sulcus thrush, which is what I assumed it was when I first saw it.
Ben had a complete veterinary checkup two days before coming to my house, he is not lame and he has always had regular farrier care. I don't hold the previous owner responsible for this as he had no way of knowing it existed. I certainly missed it until I took a knife to the foot.
I do think the previous farrier should have at least seen that there was some kind of issue, but I know the farrier in question and this is just out of his depth. He does a fair job on healthy feet, but just does not have the skills to deal with odd problems like this. I could rage against that, but there is no point. He is what he is. As are we all.
My first real hint that something was seriously wrong came when I used my hoof knife to open that sulcus crack up a bit to expose the area to air. This is what I found....
That wet, grey, nasty looking area right in the top center of the hoof is canker in it's oozing, smelly, gross state.
Be warned, the pictures get more gross from here.
The canker is a fleshy, damp growth that bleeds profusely with the tiniest of scratch.
It has a very odd, musty, fungal sort of smell.
At this point, I trimmed Ben's feet and wrapped the affected hoof with a liberal dose of Magic Cushion, which is my go-to cure-all for hoof problems. I love that stuff.
A week later, I removed the bandage and you can get a much clearer picture of the canker itself. The Magic Cushion cleaned up the nasty, grey ooze and now you can see the white canker growing in the center of the frog. There is a small amount of blood because I just barely scraped it with my knife.
By the time the vet got here yesterday, I had had the foot wrapped with the Magic Cushion for two weeks and the canker had actually shrunk because, hey, it's magic. I am even more fond of Magic Cushion now. Although, I will in no way say that this topical treatment will work on all cankers because it helped on this one. I am a big fan of Magic Cushion, but it would be remiss of me to say it will work on every case. It would certainly be worth trying, but remember what I said earlier about topical treatments either working or not with no obvious rhyme or reason.
Despite some progress with the Magic Cushion, we proceeded with the excision and cryo-therapy. Ben was sedated, given a nerve block to the foot and a tourniquet was wrapped tightly just above the hoof because cankers bleed like crazy. I don't have many photos as I was holding the foot and wielding the hoof knife, but this was taken after we cut out the canker and done the cryo treatment. The white is actually frost from the freeze spray.
This was followed by application of the crushed metronidazole pills. That was covered by gauze soaked in the benzoyl peroxide/acetone mixture and the whole wrapped in a pressure bandage. As long as the weather stays clear and the ground dry, Ben does not have to be locked in. The foot has to stay bandaged and dry, but exercise is a vital part of healthy hoof growth and he is better off outside. He is still not lame and is, in fact, feeling quite well and full of himself.
From here, I will be doing daily bandage changes to medicate the foot. If we start to see healthy tissue taking over, I will continue the medication for one-two weeks and then switch back to the Magic Cushion until the area is completely healed. If that happens, then we can put this whole crazy episode behind us and ride into the sunset.
If the canker comes back.........?