Canker is the common name for what most horse owners describe as an “ugly, smelly growth” on the bottom of a horse’s foot. People describe it as looking like jellyfish, or cauliflower, and they always mention the foul odor that hits them when they lift the horse’s foot.
Canker in horses’ hooves is one of the most confounding problems in equine podiatry today. Most horse owners have never seen it, let alone smelled it. They know something is wrong, and treat it like thrush. While thrush progressively destroys the tissue of the frog, canker appears to grow out of the bottom of the foot. Treatment with thrush medication is futile.
If canker is left untreated, the horse becomes lame and the owner eventually calls the veterinarian, who may or may not have seen it before, either--but who can deduce what it probably is. Medication and topical treatments begin, but the problem may persist, and owners’ resources may not extend to surgical debridement or repeated procedures.
Many cases of canker end in frustration for owners and pain or even sometimes death for horses. Some recover, some do not. The ones who recover may do so only to experience a recurrence of the problem, causing many owners to give up.
What is canker?
Equine hoof canker (known in equine dermatitis texts as pododermatitis chronica verrucosa or chronic hypertrophic pododermatitis) begins in the caudal part of the cleft of the frog and gradually expands to the sole and wall. Equine canker is not lethal in and of itself, but because of where it occurs on the foot, and because it can be so difficult to treat and it recurs so often, it can severely compromise a horse’s soundness. The etiology of equine canker has been a topic of discussion for many years, but the specific cause is not known.
Canker and sarcoids
In many ways, canker is similar to equine sarcoids. Like canker, sarcoids also tend to be difficult to treat and often recur. Both canker and sarcoids often include a mixture of proliferative and erosive changes in the skin secondary to overgrowth and thickening of the tissues.
Due to these similarities, it has been speculated that bovine papillomavirus (BPV) might also be involved in causing canker.
Researchers have documented the existence of BPV in hoof canker in recent research, but it does not always show up in tests. A paper by Angelique Jongbloets et al at the University of Utrecht in 2005 documented a case of a horse with canker in all four feet that without any BPV present. That case was successfully treated as an autoimmune disorder with steroid medication, and successfully recovered.
Topical chemotherapy treatment trial
Last month, the British Equine Veterinary Association (BEVA) Congress in Great Britain included a clinical research abstract authored by Apprich and Licka from the Equine Clinic of the University of Veterinary Medicine in Vienna, Austria and Department of Veterinary Clinical Studies, The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Scotland, respectively.
Apprich and Licka described using topical chemotherapy to treat canker; the same type of chemotherapy has been successfully used on equine sarcoids.
Dr. Veronika Apprich kindly shared photos and updated the study for this blog report.
The study predicted that, if successful, the treatment would both reduce the amount of time a horse would need to be hospitalized and decrease the rate of recurrence.
The initial study tracked results of treatment of three horses (two warmbloods and one draught horse). Two of the horses had canker in one front hoof; the third horse had canker in all four feet.
Laboratory tests on one of the horses identified the presence of bovine papillomavirus DNA.
The canker lesions were debrided in all the horses before treatment, but recurrence required that two of the horses underwent a second surgical debridement before chemotherapy could begin.
The horses were treated topically with a paste of cisplatin ten times, every other day, for about 20 days; the feet were kept bandaged.
In correspondence since the Congress, Apprich shared information that her team has now treated eight horses, with follow-up available on all of them. Only one horse has had a recurrence, which she explains:
“The only (and really small) recurrence (in one front hoof), which was surgically debrided in a really early stage again and by this cured until now, was seen after 13 months only in the horse with all 4 hooves affected by now; but this was also the horse which had undergone quite intensive treatment other than cisplatin chemotherapy before (at the time of cisplatin chemotherapy this horse had the 4th recurrence of canker).”
This clinical research can add to the information bank on equine canker if two ways:
- Treating more cases this way and following up on the success of the treatment may lead to a better understanding of canker and how it may be related to equine sarcoids.
- The recurrence of canker is a particularly discouraging aspect of the condition; any treatment that successfully decreases the rate of recurrence, or delays recurrence, will make a difference in owner attitude toward initiating treatment of the horse.
Thanks to Dr. Veronika Apprich for her assistance with details of her study.
Please read the full abstract for details about this treatment:
Apprich, V., Licka, T.: Topical cisplatin chemotherapy in three horses affected by canker in British Equine Veterinary Association Clinical Research Proceedings, a supplement to Equine Veterinary Journal, 2012.
To learn more:
A few papers and abstracts from the Hoofcare + Lameness library:
Jongbloets AM, Sloet van Oldruitenborgh-Oosterbaan MM, Meeus PJ, Back W.: Equine exudative canker: an (auto-)immune disease? in Tijdschr Diergeneeskd. 2005 Feb 15;130(4):106-9.
Brandt et al: Consistent detection of bovine papillomavirus in lesions, intact skin and peripheral blood mononuclear cells of horses affected by hoof cankerEquine Veterinary Journal (2), 202-209.
Moe et al; Detection of Treponemes in Canker Lesions of Horses by 16S rRNA Clonal Sequencing Analysis in Journal of Veterinary Medical Science. 72(2): 235–239, 2010
Oosterlinck M et al Retrospective study on 30 horses with chronic proliferative pododermatitis (canker). Equine Veterinary Education 23 (9), 466-471
Also recommeneded: Canker section in Equine Clinical Medicine, Surgery and Reproduction by Munroe and Weese
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