In Europe, hoof canker in horses is often nicknamed “foot cancer”. Probably due to abnormal growths and one component of all canker is papilloma virus – which is associated with sarcoids, a skin cancer. But, canker is actually a “soup” of different infections, beyond papilloma virus, so that is one reason why anti-cancer drugs like Cisplatin have not been successful in clearing horse canker.
Canker has:
Anaerobic bacteria
Aerobic bacteria
Papilloma Virus
Fungus
Proud flesh (exuberant granulation tissues)
Damaged frog/sole tissue
Spirochetes
Why canker powder’s “soup” of multiple ingredients is needed.
Only metronidazole will fail.
Only antifungals will fail.
Only cutting out abnormal tissue will fail.
What Are The Causes of Canker?
These pile up on each other to create the disease – so it’s a “soup” of causes all mixed in, with the percent of each trigger different in each case.
Viral – bovine papilloma virus
Bacterial – anaerobes, including Treponema Spirochete
Bedding in straw increases infection possibility due to organic matter being in direct contact with dirt. Also straw absorbs urine less, so more moisture allows for increased bacterial counts.
Genetic component – horse may be more prone
Drafts more prone – perhaps weight pushes dirt into crevices in foot in larger amounts. Perhaps larger foot means more prone to frog/sole wounds which allow dirt in more often.
A. Create abnormal skin/usual skin barrier is broken down to allow bacteria in
B. Live in dead/decaying organic material, so clean up any loose hay in fields, avoid straw as bedding if your horse has had canker prior
C. Use Ivermectin in the treatment regiment for horse canker. Consider using it in usual deworming program such as twice a year Equimax which has Ivermectin in it
Use shavings to dry out feet better than straw. Straw has organic dust which includes bacteria/mold and absorbs urine less, so the feet are exposed to water more. Pelodara larvae live in rotting organic debris like wet straw.
Pick feet out daily/inspect feet daily
Antiseptic
Apply Venice of Turpentine to soles of all four feet 2 times a week for life – antiseptic
Help the Barrier
Understand that the hooves/soles are extensions of the skin, so help that barrier be its best:
Health-E Vitamin E: 1 scoop a day = 5,800 IU of Vitamin E. This is the strongest Vitamin E in the USA, has all eight forms of alpha tocopherol, and is ester stable so it is good for 2 years in heat/light/air. Vitamine E is the #1 antioxidant of the epidermal tissue making up frog/sole.Why Vitamin E? Keeps immune system in peak shape in studies.
Omega 3 helps skin – add flax or chia seed to their diet – easy, simple, and cheap
Pasture
Management of pasture to decrease area of standing water
Genetic Component
Family lines of an individual horse with canker need to be inspected daily even more. If a canker horse has a brother on the program, a keep a sharp eye on them.
Deworming
Regular deworming program reduce the nematode aspect of canker – do Ivermectin 3x per year
Avoid Long Term Corticosteroid Use
Lowers immune system to allow bacteria in
What Treatments Do Not Work?
1. Caustic Chemicals
These can destroy normal tissue and create crevices that canker flourish in. They can also spill over hoof tissue onto skin of the heels/pastern and create damage.
2. Deep/Radical Surgical Debridement with No Follow Up
These require general anesthesia, so added risk and costs, and the canker will return. Often normal tissue and structures are removed unnecessarily.
3. Maggot Therapy for Cleaning Out Necrotic Tissue
This treatment cannot reduce proud flesh aspect of canker or kill harmful bacteria of the disease. This therapy usually also requires surgical removal of some abnormal tissue prior to maggot placement. A better option is the surgical removal of abnormal tissue and placement of horse canker powder.
4. Freeze Firing
Often requires multiple separate treatments due to canker reoccurs. This therapy also requires surgical removal of canker tissue prior to the procedure and often, topicals are required after freeze firing. A quicker, easier way is surgical removal and placement of horse canker powder.
5. High Dose Oral Corticosteroids
One study suggested this to help in reducing proud flesh aspect of canker but it’s a therapy with problems:
Immune Suppression Caused by Steroids: This can increase bacterial infections. Also Cushings horses should avoid this due to raising of glucose levels and their cortisol levels are already high. In addition, corticosteroid reduces muscle mass by breaking it down to create glucose, so it is not helpful in older horses with muscle problems.
Laminitis: Increases insulin, so it is not good for insulin resistant horses and can increase laminitis episodes in IR horses.
Proven to create IR in normal horses with extended use.
6. Chloramphenicol Topical Antibiotic
Human Health Hazard. Other antibiotics like SMZ-TP, tetracyclines, metronidazole, and ketoconazole are much safer.
Expensive
7. The Use of Cisplatin Anti-Cancer Agent to Treat Horse Canker
“Cisplatin may lead to diverse side effects such as neuro and/or renal toxicity or bone marrow-suppression”
“Despite the positive effects of platinum compounds, they are poisons”
“Cisplatin creates DNA damage to tissue – considered a DNA-damaging anticancer drug”
Due to the potential to damage normal tissue on the hoof or horse skin if split or runs accidentally onto it; and the multiple (at least 14) times you need to handle it as a veterinarian, along with the dangers to human skin and bone marrow problems, it’s wise to look for other safer treatments for horse canker. Also, this treatment cannot be done at a barn or stable – it would only be at a hospital, so costs would be much greater.
Euthanasia
The need for past euthanasia often was due to the lack of recent knowledge that we have now. More accurate trimming of necrotic tissue, correct antibiotics, the importance of keeping dry are adding up to increased success.In the recent past, canker was often a grave prognosis:
1962 – Lameness in Horses (Dr. Adams)
“Guarded to unfavorable prognosis”
1998 – The Lame Horse (Dr. Rooney)
“Less than hopeful prognosis”
More and more, euthanasia is not being considered due to canker getting cleared up.
Equine/Horse Canker Studies
1. Dr. Evans Study Presence of Treponema on hooves is NOT diagnostic of canker in horses.
Cattle that had PCR biopsy of skin near the hoof that were negative for treponema, still had positive PCR for for treponema on healthy hoof tissues. These cattle were brought to a farm with cattle with present cattle digital papillomatous dermatitis levels.
This means a simple culture of treponema of a horses foot will NOT mean it’s canker positive.
This also means that treponema are present in the dirt at a farm with a horse with canker most likely. Whether treponema is ubiquitous (all over) to all horse farms is unknown. Whether the load/amount of treponema at a farm contributes to more canker is unknown.
Presence of cattle digital dermatitis bears important information to consider in horse canker.
Cattle digital papillomatous dermatitis is worldwide – so is horse canker.Cattle digital dermatitis has the same treponema found in horses. Treponema denticola-like spirochetes found in diseased cattle digital dermatitis (76.5% of cases).79% of human endodontic (gum line) abscess showed PCR genetic testing also for treponema denticola.
This treponema spirochete effects many animals – humans, horses, dogs
In cattle, they isolated several species of treponema in diseased tissue – not just treponema denticola. It’s very possible more treponema species than just treponema denticola-like will be found in horse canker
In cattle papillomatous Digital Dermatitis in a Japan study, 40 different spirochete strains were found
Cattle papillomatous digital dermatitis creates hyperkeratotic papillomatous lessons with long hair like projections – this is the same thing found in horse canker
Many different types of bacteria cultured in BPDD – unclear whether some or all involved, but a large number of spirochetes found.
Culturing out treponema in diseased tissue is a difficult process due to growth rate of treponema being poor.
Also, presence if other fast growing bacteria in lesions prevents treponema isolation. No selective growth media for these treponema has been developed
So if culturing and have a treponema negative result, that does not mean they were NOT present.
Did find systemic antibodies against certain spirochetes in diseased tissue, so an immune response is being made, but it may not be protective or due to so many species of spirochetes, the genetic diversity is so great that it evades immunological responses to clear infection.
Treponema denticola is a key pathogen in human periodontitis (gum) disease.
This spirochete creates a large inflammatory reaction to tissues around it – TNF, IL-1, IL-6, IL-8, MMP, prostaglandins are pro-inflammatory cytokines that all increased.
So in horses, it’s setting off inflammation in hoof canker tissue.
Metronidazole antibiotic indicated against certain anaerobic infection, safe in humans, widely used.
When studied between just cleaning, just metronidazole, or cleaning and metronidazole, the cleaning and metronidazole dropped infections the most – by 79% – they did not eliminate it, but there was a huge reduction.
Metronidazole treated people also had less bleeding of gums post treatment.This is why metronidazole is important in canker therapy of horses.
Treponema denticola actively detaches fibroblasts from gum tissue, leading to tissue detachment. It is actively destroying tissue – this allows other bacteria to move in.
Metronidazole helped to “markedly reduce the detachment response”.
Metronidazole helps in protecting tissues infected with spirochetes.
Using metronidazole topically is effective and safe, even on human faces to treat acne. Had a 88% patient satisfaction and redness on face decreased by 85%.
A study mixing metronidazole with benzoyl peroxide for acne showed good effects over an 8-week period. Again on human faces, this combination was safe.
Benzoyl peroxide is an active ingredient in Clearasil used in teen acne
Comment from Dr. Reilly: Some vets report results if they first do a surgical resection of the area, followed by Freeze Firing and then applying metronidazole/benzoyl peroxide mix
The Role of Doxycycline Treatment?
Use of Tetracyclines to help in human treponema periodontitis infections
Doxycycline helped – cleaning/debriding area alone did not help – need doxy added
Found that diabetes that were treated had better glycemic control. This may be of interest in IR or cushing horses – reducing infection, reducing pain of canker may help in these diseases.
The correct dose of Doxycycline is 10 mg/kg body weight every 12 hours. This means in a 1,100 pound horse, the dose is 5 grams AM & 5 grams PM.
Comment from Dr. Reilly: So, foil pack of 5 grams each are easy, cheap, and helpful.
The Role of Treponema Spirochete?
Treponema is a probable canker component around the world.
1. Treponema denticola-like spirochetes are also found in other parts of the world such as in the UK. PCR testing of diseased cattle Digital Dermatitis found it in 76.5% of cases
DNA testing of horse canker showed in 24 of 24 cases of Bovine (cow) papillomavirus (BPV)
Viral sequencing is 98% BPV in horse canker
Testing of horse tissue with no signs of canker showed 13 of 13 times , no BPV
Conclusion: BPV is an active contributor to horse canker. BPV in cattle produces many of the signs seen in horses such as hyperkeratosis, acanthosis, and moist pododermatitis
3. In comparing miconazole and ketoconazole topically on skin against Candida Fungus, ketoconazole produced 14 x, 10 x, and 7 x greater drug concentrates at 1, 4, and 8 hours than did miconazole
4. Ketoconazole had significantly greater bioactivity than did miconazole
5. Ketoconazole had greater efficacy than miconazole
6. Ketoconazole used against seborrheic dermatits and it improved erythema (redness), scaling, and pruritus (itch)
7. Ketoconazole reduced symptom severity 53%
8. Ketoconazole found to be effective, well-tolerated, convenient and acceptable treatment
9. Animal studies indicate topical ketoconazole was very active in the most common skin infections10. Not reported to give dermal absorption and was not toxic to animals
Some horses may have infectious osteitis of the coffin bone, if the canker infection undermines the full sole thickness. This requires possible bone surgery, high powered antibiotics. Often in these, Naxcel is very helpful.
Some horses may have secondary laminitis on top of just the canker
Some horses may have bits of rock that jam up into/or under the sole and the horse will stay sore until removed.
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