“No hoof – No horse”

Quotation of Philippe Etienne Lafosse (Hippiatrics Course, Comprehensive Treaty of horse medicine, 1772 – France).

The frog thrush affection is mostly due to a lack of hygiene or a poor hoof care, although some horses seem to be more prone to developing this pathology than others.

Horses with hooves not sufficiently cured or with deep collateral grooves, as well as those whose stalls are not sufficiently maintained, are the most exposed to this disease.

Dirt accumulated in the grooves rots, making the frog rot too, and the latter becomes black and spongy with a foul smell. The infection then moves up to the horn, which darkens and softens.

This highly-common pathology affects an average of five million horses in the United States and four millions in Europe every year.

The infectious origin of the hoof thrush (in general) and of the frog (in particular) is bacterial as well as (fungal).

Over the last twenty years, several university research centers (in Canada, the United Sates and Europe – including ours in Belgium) focused on this pathology in order to better understand it and bring innovative solutions.

Summary of the researches conducted on this disease:

Dr Kuwano and his team conducted a study with samples taken from rotten hooves. Having done fine histological sections, they were able to show for all lesions that irregular spaces were covered with basophilic bacteria, i.e. bacteria living in alkaline environments.

On horses suspected to suffer onychomycosis (infections due to fungi), seven out of ten samples revealed the presence of Scedosporum Apiospermum and/or Pseudallescheria Boydii (considered as teleomorphs of Scedosporum Apiospermum, i.e. its development to the sexual stage).

This team also isolated Genius Scedosporium, a fungus producing a protease which attacks and dissolves the horn in 70% of the cases. Proteases are enzymes destroying and breaking the peptide links of the proteins.

Dr Michael Wildenstein’s team isolated other strains of fungus, as Trichoderma sp, Mucor sp, Aspergillus Glaucus and Gliocladium sp.
All these fungi (this is a non-exhaustive list) identified on rotten hooves are cosmopolite fungi which means they are found in most areas of the world.
They are aerobic; therefore they live in presence of the air oxygen.
They live and develop on various substrata high in organic matter: beddings, manure, excrements, sludge, waste water, vegetal waste, etc. which is the reason why they are also called “saprophagous”.
On the human body, they often colonize the bronchi of children suffering cystic fibrosis.
They are also opportunists in immunosuppressed individuals (transplanted persons or patients on prolonged corticosteroid therapy).
They cause visceral lesions (central nervous system, endocarditis), arthritis, keratitis.

Other teams, as Dr Bellington’s, Dr Fontaine’s and Dr Liu’s focused on the bacterial aspect of the foot infections.
Several pathogen anaerobic strains (living away from air oxygen) were identified, as Fusobacterium Necrophorum or Dichelobacter Nodosus.
Among the samples collected on the affected tissues, they noticed that most of these bacteria live together and at least ten strains were identified.

Most of them don’t survive on the ground for more than a few weeks, and to do so they need dampness and a temperature exceeding 10°C.
Species as Fusobacterium, for example, are part of the normal flora of the oropharynx, digestive tract and genital tracts. Infections can occur after surgical or accidental trauma, edema, anoxia, destruction of tissues and animal bites. They are found on human-beings as well as on animals, including horses, cattle, sheep, goat, pigs and poultry.

Fusobacterium is responsible for the Lemierre syndrome, a rare but serious pathology of the human body. It is a post-angina septicemia causing fever, cervical pain and pulmonary symptoms. It is also responsible for 10% of acute sore throat syndromes, and 21% of recurring sore throat syndromes.

Bacterias like Fusobacterium can survive for as long as eighteen weeks. They survive well in a wet ground rich in manure. However, studies on aerated faecal sludge demonstrated that concentrations of Fusobacterium were lower than the detection threshold after twenty-four hours. In non-aerated faecal sludge, no change was observed regarding the concentrations of Fusobacterium within the first twenty-four hours; however, they completely disappeared after six days.

As for Dichelobacter nodosus, it is featured a high proteolytic action (protein hydrolysis) and this bacteria synthesises several proteases. The virulent strains produce four serine proteases which are acid and thermo stable ((VA) V1, V2, V3, V5) and one basic protease (BprV). The strains with a low pathogen action excrete five acid and thermo labile proteases (B1, B2, B3, B4, B5) and one basic protease (BprB) very similar to BprV.

Virulent strain proteases are active on casein, collagen, elastin, fibrinogen, gelatine, haemoglobin and keratin. These proteases are implied in the formation of the lesions, and on this aspect the most important ones are Keratinase, which degrades keratin (major component of the hoof), Elastase, which substrate is elastin (major component of the ligaments) and Gelatinase, which hydrolyses gelatin (major component of the conjunctive tissue).

The virulent strains also contain an active polysaccharide called LPS. It is responsible for the inflammatory reaction within the cartilage and conjunctive tissues.

Dichelobacter nodosus also produces toxic amines (ptomaines) which may favor its spread, as well as putrescine, responsible for the characteristic odor of the lesions.

Treatments

Prevention:

Prevention consists in ensuring a daily cleansing of the box and cleaning out the hoof regularly. Poor-quality pastures shall be avoided too.
It is also important to visit a farrier or a vet without delay. A regular follow-up by the farrier (when renovating the horseshoes for example) is also highly recommended.
Every treatment first consists in cleaning the hoof out properly and deeply in order to scrub off all the visible rot as well as all the necrotic tissues.

Antibiotics:

Antibiotics for internal or external use as oxytetracycline, metronidazole, or penicillin. Although their efficiency is well-demonstrated, recent studies have shown the emergence of more and more frequent resistance to antibiotics.

The latter will be reserved for the treatment of the most serious cases.
For several years the European Union has encouraged the research for new natural treatments to replace the use of antibiotics.

Local treatments (topics) :

A great variety of local treatments exist in the equestrian tradition.

These include the Villate liqueur, copper sulfate in aqueous solution, hydrogen peroxide (oxygenated water), Formalin, bleach (sodium hypochlorite), tincture of iodine, or even sulfuric acid!

The use of Villate liqueur has been prohibited in the European Union for several years, as its formula is highly toxic and its efficiency quite mediocre.

Copper sulfate solutions are also prohibited because of their environmental toxicity. The main problem with the other remedies mentioned here above is that they are aqueous solutions, and therefore difficult to keep in extended contact with the infected areas. To do so, they often require the use of wraps, bandages, or swabs to be renewed regularly. Some of these compounds can be highly aggressive and very painful. It is the case with hydrogen peroxide, Formalin and of course sulfuric acid.

Another commonly-used product is the Norwegian tar, also called pine tar, officinal tar, vegetal tar, or liquid pitch. It is made from charring pine in the absence of air before distillation. It is a black, viscous and sticky product.

From what we have observed, Norwegian tar is really to be avoided as a first-line treatment, as it often worsens the situation. Indeed, it favors the proliferation of anaerobic bacteria as it isolates the infected area from the outside environment. Without mentioning the fact that it is very hard to scrub off.

Towards a new therapeutic approach: Hoof Solution

Our research consisted in creating an unguent which is stable, sticky, easy to use (to apply with a small brush), with no need of bandage, swab or compress in most cases.

The scope of Hoof Solution is very large (fungal as well as bacterial), and it doesn’t cause resistance as antibiotics do.
It is a safe, non aggressive, environmentally friendly and totally natural product.

It is also recommended in a preventive use (once a week).

The results of the studies lead with Hoof Solution were shown in various scientific presentations during international congresses of veterinarian medicine and horseshoeing.