Rain Scald, Rain Rot, Dew Poisoning, Mud fever, Dermatophilosis, Streptothricosis – What do these conditions have in common?
They are essentially the same thing caused by the same bacteria – different names have arisen from different parts of the world and different locations of outbreaks on the horses body.
Coming from Scotland this is something we would have to frequently treat. Luckily Alberta is a much dryer place, however I am still coming across some mild cases.
This common type of skin infection has several names but is always caused by a bacterial organism called dermatophilus congolensis. This organism lies dormant in the skin and is activated when the skin is compromised by high moisture environments, prolonged wetness, high temperature or attacks by biting insects (according to The Merick Vetinary Manual). Often it is more discoverable at this time of year when our horses are shedding their thick winter coat, which often acts to trap moisture next to the skin and then hides the condition. It can thrive in common sweaty areas under the saddle pad and girth, which then becomes a problem for riding. The wet and muddy conditions of spring-time also make this more common especially in the skin on the horses heels.
What does it look like?
In the early stages this feels like small hard lumps on the horses skin and hair. These can be small or large in size and form scabs which when removed take the hair with them (also described as paint-brush lesions). Depending on the depth of the infection when the scabs are removed skin is inflamed and can ooze serum (pus). Usually it appears on the horses back and rump, along the back of the fetlock (dew poisoning, mud fever, pastern dermatitis or greasy heels) and the front of the cannon bones. Areas of white skin are more susceptible.
How should I treat this?
You’ll be glad to hear that this bacteria is susceptible to most of the commonly used anti-bacterial solutions. The bacteria live underneath the matted scabs, so it is important that these are removed as it cannot thrive in dry oxygenated environments. However this can be very painful, so soaking them in an antibacterial solution or warm soapy water first will help soften the scabs and make them easier to remove. If the hair is long, then clipping the area or trimming it with scissors will help. The skin should then be dried thoroughly and an antibacterial ointment applied along with a moisture repellent cream (although you need to be very careful not to trap any moisture in). The area should be kept as dry as possible. In very severe cases a vet will need consulted and antibiotics prescribed.
Can this be prevented?
Of course prevention is better than cure! This infection can spread from horse to horse, so (as always) practicing good hygiene habits is essential. Do not share grooming brushes, rugs, boots or saddle pads between horses. Regular cleaning and disinfecting these will also help prevent recurrence. Be sure to wash your hand before and after treatments. Obviously keeping your horse as dry as possible is very important – make sure wet rugs are not left on and horses are not sweating under rugs. Muddy pasture conditions should be avoided, or use water repelling lotions to protect the skin.