Rainscald

Rainscald (also known as dermatophilosis, rain rot and streptothricosis[1]) is a common skin disease in horses that is caused by Dermatophilus congolensis.[2] This is the same organism that causes Mud fever in horses. This disease is very common in cows, sheep and goats and is also found occasionally in cats, dogs, and humans. D. congolensis is a gram-positive bacteria that is thought to originate from the soil. It commonly causes disease in moist, tropical areas, but can also be found in wet northern environments.[3] Moisture and high temperatures facilitate the dispersal and penetration of zoospores into the skin, contributing to the spread of the disease.[4] Ticks, biting flies, and contact with other infected animals also causes the spread of rainscald.[5] Once in the skin, the bacteria cause inflammation of the skin as well as the typical symptoms associated with rainscald.

Symptoms

There are two different manifestations of rainscald: the winter form, which is more severe due to the longer coat of the horse, and the summer form, which is less severe.[4] Horses are usually affected on the back, head, and neck, where insects commonly bite, and the legs, which are commonly infected if the horse is kept in moist footing.[2] Initially, the horse will display a matted coat and bumps which will then progress to crusty scabs and lesions.[3] The animal may also be itchy and display signs of discomfort.

Diagnosis

Diagnosis is most commonly done with the identification of bacteria in the lesions by a microscope observation.[5] Ticks, biting flies, and contact with other infected animals also causes the spread of rainscald.[2] A scab will be taken from the affected animal and stained so that the bacteria are visible under a microscope inspection.[5] A positive diagnosis of rainscald can be confirmed if filamentous bacteria are observed with as well as chains of small, spherical bacteria.[3] If a diagnosis cannot be confirmed with a microscope, blood agar cultures can be grown to confirm the presence of D. congolensis.[5] The resulting colonies have filaments and are yellow in colour.

Treatment

Rainscald normally heals on its own, however as the condition can spread to involve large areas, prompt treatment is recommended. Although some cases can be severe, most rain scald is minor and can be easily and cheaply treated at home naturally.

First groom the affected parts carefully, to remove any loose hair. Be extremely gentle, the area is very sore itchy and horses will very quickly get fidgety. Next shampoo the area, use warm water and a soft cloth or brush, and massage the lather through the coat as much as the horse will tolerate. It is best to use Neem shampoo here, as this will treat as well as clean, but any mild shampoo is fine. Remove as much water as possible and dry the horse off, either use a hair drier or let him/her stand in the sun until completely dry. It is important not to let the horse roll! The rain scald bacteria may be picked up from the soil.

When the horse is completely dry, gently brush off any more loose hair. Next apply a salve or cream containing a high percentage of neem oil, or even pure neem oil, to liberally coat the affected area. Rub it in using fingertips, massage the area as much as the horse will tolerate. This will be very greasy. Smooth the hair back down and apply a rug to keep the horse dry, this prevents the neem being washed off as well as protecting from more dampness issues. Turn the horse out as normal.

Check it every day, and reapply the neem salve/cream if it seems to have dried away. The area should remain greasy with neem. Every 2–3 days or so, go through and scrape/pick off as much of the scabs as possible without upsetting the horse or making it bleed, then reapply the neem. Typically there will be improvement in a few days, and in a week there'll be some sign of new hair growing back. More severe rain scald may take longer.

Once all the scabs are gone and there is new hair fuzz growing in all over, use neem shampoo to clean the area of greasy residue, and dry well. Keep the horse covered for some time after rain scald has been treated, particularly in wet weather. Do not allow the skin to remain damp. It is advisable to shampoo the horse after riding or exercising, to remove sweat, which may encourage rain scald conditions, and make sure the coat is completely dry afterwards.

This treatment works in many ways. First, shampooing cleans the area of any contaminants, remove a lot of loose hair and scabs, and the rubbing stimulates the circulation. The neem is an antifungal agent, and works to eliminate the bacteria that cause the infection. It soothes the irritation in the area, and its greasiness provides the ideal environment for the raw skin to heal and grow new hair. It also helps to soften and lift the scabs. The new hair cannot grow in until those scabs are removed from the surface, but they are very painful to pick and remove, and most horses are intolerant of this procedure. After the neem has soaked into these scabs they will come away much more freely, and soon new hair will grow through.

In conventional treatment, scabs are softened with benzoyl peroxide and chlorhexidine and removed in order to speed the healing process.[3] In severe or chronic cases, penicillin and streptomycin are injected into the horse to kill the bacteria.[3]

Typically the disease is not life-threatening, nor does it impact the welfare of the horse, so treatments are more for the owner's sake of mind and cosmetic appeal of the animal.[3]

Prevention

In order to prevent rainscald, it is important to stop the spread of the bacteria. Tick and insect control is an effective way to stop the spread of the bacteria from one animal to another.[5] As well, separating infected animals will help to stop the spread of the bacteria.[2] Keeping the animal in a dry, well-ventilated area out of the rain and wet conditions will stop the bacteria from growing.[3] This dry environment includes dry ground as well as dry air.

References

  1. ↑ Macadam, I. (September 1, 1970). "Some observations on bovine cutaneous streptothricosis in Northern Nigeria". Tropical Animal Health and Production. Kluwer Academic Publishers. 2 (3): 131–138. doi:10.1007/BF02359679.
  2. 1 2 3 4 "Fast Facts: Dermatophilosis" (PDF). The Center for Food Security & Public Health Iowa State University. January 2006. Retrieved 10 November 2011.
  3. 1 2 3 4 5 6 7 "Dermatophilosis: Introduction". The Merck Veterinary Manual. Merck SHarp & Dohme Corp. Retrieved 10 November 2011.
  4. 1 2 Szczepanik, Marcin; Marcin Golynski; Dorota Pomorska; Piotr Wilkolek; Iwona Taszkun; Marcel Kovalik (2006). "Dermatophilosis in a horse - a case report" (PDF). Bulletin of the Veterinary Institute in Pulawy. 50: 619–622. Retrieved 10 November 2011.
  5. 1 2 3 4 5 "Dermatophilosis" (PDF). OIE. 2008. Retrieved 7 November 2011.
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