| Mud Fever & Rainscald - The Same Bug! |
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By Stephen Champion, BSc (Hons) BVM&S MRCVS, The common skin conditions of horses called Mud Fever, Rain Scald and Greasy heel are caused by the same bug, a bacterium called Dermatophilus congolensis. This group of skin conditions (collectively called Dermatophilosis) are thus related and represent some of the most frustrating skin conditions for an owner and veterinary surgeon to deal with. They can be debilitating, expensive and time consuming and a preventative approach coupled with rapid and effective treatment when required are the best ways to avoid a real headache! Greasy Heel (and the more severe form called Mud Fever) affect the lower limbs, particularly the pasterns but also further up the leg. Rainscald affects mainly the back. Both diseases are characterised by patchy hair loss, crusting, dandruff of the skin and occasionally irritation. In more severe cases the horse can become depressed and even have a raised temperature. The affected limbs may be swollen and covered with a multitude of tiny scabs, felt as small lumps in the skin. The skin can appear reddened and large areas can be covered. In severe cases I have found the horse to be lame with mud fever. Take great care in feathered horses to look deep under the feathers, as the condition can easily be missed. Usually, affected horses have been exposed to persistent wetting, such as rain, muddy paddocks or an accumulation of sweat under rugs. They are also exposed to some kind of minor skin injuries, such as tack abrasions, sharp vegetation or biting flies, since this is how the bug gains entry to the skin. Dermatophilus enters the skin through abrasions after it is acquired by your horse from biting flies or transmitted in the scabs from “carrier” animals grazing on the same pasture. Beware - infected scabs can survive on the pasture for up to 42 months – so the culprit may be long gone! Once in the skin, the bacterium multiplies and causes the disease before finally being eliminated by the horse’s immune system – but not until after much heartache! It is important to know what you are dealing with, so that the correct treatment can be administered. More that 20 different conditions that I can think of may be confused on first inspection with mud fever or rainscald, such as allergies, parasitic infections, sweet itch, vasculitis, and infection with other bacteria. In all but the most mild and transient cases, a veterinary diagnosis and treatment plan is the most “pain free” method of quickly eliminating the disease. In almost all suspect cases, I take hair plucks and smears for staining and examination under the microscope – the bacterium has a characteristic appearance which can be recognised if present. There are many, many different treatments available and recommended for dermatophilosis, which as usual means that no one treatment is guaranteed to work in any one situation! For large areas, my preferred course of action is firstly to stable the horse (unbandaged) away from the wet and the flies. Large affected areas are treated with either “Hibiscrub” solution, or a shampoo containing benzoyl peroxide (which is marketed from dogs but foams well and covers large areas easily). Leave in contact for 20 minutes before rinsing and drying thoroughly. I suggest repeating daily for about a week, then weekly until the condition is cleared up. When scabbing is severe, I advocate hot, wet poulticing for two to three days, changing twice daily, followed by bandaging with dry poultice dressings until the raw wounds are healed. Remember to dispose of the scabs carefully due to their long period of infectivity off the horse – otherwise you may not make yourself very popular on the shared grazing! For smaller or more severely-affected areas, one of the antibiotic creams is useful and will be obtainable from your vet. Try to avoid creams or ointments containing corticosteroids, such as prednisolone or dexamethasone. The horse’s immune system working locally in the leg or back to literally “eat up” the infection, will be suppressed by such medications. However! On occasion for very persistent, localised infections, (when the owner is about to consider changing vets!), I have reluctantly used steroid-containing preparations (such as the well known green one!) to miraculous effect. Horses for courses, I guess! I have even been told by a reputable source that a mixture of pig oil and sulphur is cheap and effective treatment when painted on – another treatment which I am more than likely to try it the future. In severe or very recalcitrant cases, antibiotic courses by mouth or by injection for seven to 14 days are a realistic option. And remember the sun-block for white-skinned horses where sun-induced skin disease can be an associated problem. Prevention involves avoiding the initiating factors as mentioned above, particularly in “carriers” where flare ups can occur from time to time. Ensure bedding is dry and non-irritant, avoid sharing grooming kits and rugs and dispose of those scabs properly! Isolate affected horses to another part of the field of stable block and I always advise keepers of multiple horses to do the affected ones last, to avoid trampling infected material into other stables. The prognosis for a full recovery is good, so long as the correct diagnosis is made and the appropriate treatment administered. Spontaneous recovery often occurs in two to three months and is often coincident with the owner starting to lose his own hair (usually by self-inflicted extraction!). Recovery is often, I have observed, also coincident with the application of the last ditch “miracle cure”! Failure is usually associated with inadequate disinfection of tack, repeated exposure to wet, or the chronic carrier not being identified, so attention to detail, as with so many things, cannot be underestimated. |
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