Rainrot – when strange crusty bumps appear on the horse’s back

Reading time 6 minutes

Rainrot is also known as rain eczema or, in some cases, rain mange, and is often not initially recognised by most horse owners, therapists and vets when confronted with the condition the first time. This infection of the horse’s skin occurs more frequently in the wet weather season when horses with long (winter) coats are permanently damp. The occurrence of rainrot is also not uncommon after long periods of rain in summer, when horses are standing on summer pastures without shelter. Hair loss that follows the infection is often initially thought to be a fungal skin infection. In case of rainrot it’s bacteria not fungi that causes the skin irritations.

Bacteria on the skin

‘Dermatophilosis’ is the medical name for this disease. The bacterium Dermatophilus congolensis is responsible for it. It is actually part of the physiological skin condition, so it is always present on the horse’s skin. If, however, there is constant rainfall, and the horse doesn’t get a chance to dry off thoroughly for a longer period of time; perhaps the immune system is already overloaded, the bacterium can easily take the upper hand. The persistent wet condition attacks the skin in the long term, causing micro-lesions, tiny injuries so to speak. The warm and moist coat provides optimal conditions for the bacteria to grow. The bacteria can penetrate the micro-lesions in the skin and spread rapidly, leading to large-scale inflammatory reactions.

What does the infection look like exactly?

Small pustules from large areas and amber-coloured crusts can appear, the skin is red in colour, swollen and warm and painful to touch. At the beginning of the disease the crusts often go unnoticed as they are well hidden under the coat. As the disease progresses, the crusts become thicker and more noticeable, the coat appears to stand up vertically, making the horse even less able to protect itself against (constant) rain. After a short time, the hair falls out due to the skin infection and the full extent becomes visible.

In contrast to fungal skin infections, dermatophilosis does not usually lead to itching and scaling. The inflammation with crust formation, hair loss and sensitivity to touch are the main symptoms.

It mainly spreads over the back, head, neck, and hind legs, where the horse gets wet when standing in the rain. However, without any treatment and depending on the general condition as well as the state of the immune system of the horse, the infection can spread over the entire body. In such cases, horses can also suffer from fever and apathy. For this reason, horses that live out in summer 24/7 should be regularly checked, especially during long periods of rain.

How can I help my horse?

In severe cases of infection accompanied by fever and severe pain, it is essential to consult a vet. Once the vet has confirmed the diagnosis, he can prescribe appropriate medication. It doesn’t always have to have such a drastic result. The earlier any changes in the coat can be spotted, the easier it is to treat.

The patient should then be dried thoroughly, and kept dry for the foreseeable future, to prevent the infection spreading further. Stabling may be necessary until the disease is completely cured. Generally speaking, this disease is contagious to other horses in the heard as well as to humans. The risk of infection is generally lower compared to a fungal skin infection. The bacteria need an entry point into the skin, and this usually only occurs if the skin is damaged by prolonged wetness. Hence the name ‘rainrot’, as the disease occurs almost exclusively in rainy weather conditions. Usual hygiene measures and precautions apply.

Open areas on the skin where the wound secretion is visible should be thoroughly disinfected with a suitable disinfectant. Creaming with very greasy ointments should be avoided, as the bacteria can multiply under the layer of fat applied. If the horse has a very long coat, clipping the coat back can be useful to allow air to reach the skin and speed up the drying process, and thus interrupt spreading the infection further. Clipping especially in the winter may be unavoidable one to access the degree of severity and two to allow treatment to the wounds. Equipment, such as clippers and the corresponding blade that have encountered an infected animal should be disinfected after use. Treatment must be carried out daily and can take up to several weeks, depending on the horse’s condition.

An Equine appropriate diet can have a positive influence on recovery

The most important element is to support the horse ‘from the inside’ and strengthen the immune system. An Equine appropriate diet with sufficient mineralisation can have a positive influence throughout the recovery from the disease, it can also act as a prophylaxis. Colon restoration measures can help to relieve the immune system and thus accelerate healing. Essential fatty acids, for example from various seeds with a high oil content such as sunflower seeds, linseed, rosehip seeds or wild seed mixtures, can support the fatty layers in the skin from the inside and thus have a preventative effect without placing an additional burden on the organism, as it happens in the case of feeding oil.

Conclusion

The therapy in recovery is lengthy, the best cure is prevention best to check the horses frequently in case of long wet periods to avoid any manifestations of dermatophilosis infection. It is advisable to use adequate protection from persistent wet weather conditions. Once a horse has fallen victim to a previous skin condition, they are more susceptible to contract dermatophilosis. Horses that previously have experienced conditions such as (summer) eczema, nettle rash or similar are most venerable. In such cases sufficient support for the immune system is vital, a competent therapist should be consulted to find the best support forward for the horse and its individual needs.