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Rain Rot in Horses 101: Treatment and Prevention

Dean Eby

February 5, 2021

If you’ve been around horses long enough, you’ve almost certainly heard of rain rot. It’s one of the most common skin infections that affect horses, though it’s often mistaken for a fungal disease. It’s easily identifiable by the scabs that appear in the affected area, and luckily, it’s a pretty easy to cure condition. In this article, we’re going to cover a wide range of topics regarding this infection, including how to prevent it from affecting your horses and even how to treat it should infection occur.

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What is Rain Rot?

You may have heard rain rot called by other names, such as rain scald or streptothricosis. This condition is caused by an infection of the organism dermatophilus congolensis. Often mistaken for a fungus, this organism is actually an actinomycete, which has traits of both fungi and bacteria.

This actinomycete creates scabs in the infected areas, causing hair to be lost in small tufts. The condition is not life-threatening, so your horse is safe. However, care should be taken not to let anything rub against the scabs, such as a saddle.

The scabs aren’t painful for your horse. Surprisingly, they haven’t been shown to cause itchiness either. But if they’re rubbed against, the scabs can fall off, leaving pink, pussy skin unprotected where the scab was removed.

horse rain rot
Image Credit: Napat, Shutterstock

How Does Rain Rot Occur?

The dermatophilus congolensis actinomycete is the main culprit of rain rot, but it doesn’t cause problems in all conditions. This infection is called rain rot because it requires a warm, moist environment to multiply and take hold. These actinomycetes live in the horse’s skin, but they don’t generally affect the horse until the skin becomes compromised.

This can occur through several means. If your horse is wet for a long period, that can be the catalyst necessary to allow rain rot to take hold. Other things that can compromise your horse’s skin include excessive humidity, high temperatures, and even insect bites.

Regional Rain Rot

Because rain rot is so environmentally dependent, it’s far more common in certain locales. Some regions rarely see rain rot, such as arid desert regions in the southwestern portion of the United States. More humid places that see higher amounts of rainfall will see far more cases of rain rot. This includes places like Florida and any coastal states where humidity is often high and rain is a regular occurrence.

How to Identify Rain Rot

The hallmark of rain rot is the scabs that appear when infection occurs. But this isn’t the only clue to aid in your diagnosis. Furthermore, scabs can also be present with other skin infections, so your diagnosis isn’t guaranteed to be accurate.

Horses with long winter coats won’t develop scabs the same as horses with shorter summer coats. Instead of seeing large scabs, you’re more likely to notice matted tufts of raised hair that are referred to as paintbrush lesions. These lesions will grow and multiply with time, eventually forming one large scab with visible pus excretions between the dead and living layers of skin.

The most surefire way to diagnose rain rot is to examine a scraping of the skin under a microscope. Alternatively, you could culture the bacteria. These methods can practically guarantee an accurate diagnosis, though you’ll probably have to have a vet perform the procedure.

neglected domestic horse
Image Credit: Eric Buermeyer, Shutterstock

Will it Heal Naturally?

For many people, when a health concern arises, the natural inclination is to see if it works itself out. When it comes to rain rot, this isn’t a healthy approach to take. Instead, you’re far better off nipping it in the bud and taking action the second you notice an infection starting to set in.

That said, some horses can naturally rid themselves of this infection. Since it’s caused by an organism living in the skin, as a horse sheds its winter coat, the organisms are sometimes forced out, but this isn’t always the case.

Consequences of Rain Rot

There’s good reason why you should treat rain rot immediately. Even though some horses can cure it with the shedding of their winter coat, if the infection isn’t cleared up quickly, it can lead to even worse problems.

Rain rot needs a hot, moist environment to survive. These conditions also happen to be a breeding ground for other bacteria, which is why secondary infection is so common when dealing with rain rot. The most prevalent secondary infections are staph and strep. Unfortunately, these infections can be more dangerous and even harder to treat than rain rot.

Spreading the Infection

One of the worst things about rain rot is how easy it is to spread. Since it’s caused by an organism, if that organism is transferred to another horse, that horse will also end up with rain rot. This means that any shared equipment between horses is practically guaranteed to cause multiple infections.

If a horse has rain rot, you’ll need to ensure that no other horses come in contact with any equipment used on the infected horse, including saddles, saddle pads, leg wraps, brushes, halters, and any other piece of tack. It’s recommended that you thoroughly disinfect each piece of equipment immediately after an infected horse uses it.

Insects can even spread rain rot from horse to horse. They bite one horse, then fly over to bother another, transferring the infection along with them. So, even if you do your best to avoid cross-contamination, the insects might cause it anyway.

rain scald on horse
Image Credit: Dima Oana Gabriela, Shutterstock

Curing Rain Rot

The organism responsible for rain rot requires moisture and heat but it hates oxygen. In fact, it can’t grow well or reproduce as much in a high oxygen environment. We can use this information to our advantage when attempting to cure rain rot.

Your horse will need to be kept in a dry and clean area. Preferably, one with a moderate temperature. It must be well ventilated, but also provide protection against biting insects. Most importantly, the horse must be kept away from other horses, infected or not.

Antibacterial and antimicrobial shampoos are your first line of defense. Lather your horse well and allow the shampoo to sit for 10-15 minutes so it can start killing the infection. Then, rinse your horse thoroughly, being careful to dry them completely afterward. You’ll need to repeat this process daily for at least a week.

You’ll also need to remove the scabs from your horse. This can be quite painful though, so you’ll need to work slowly and gently. It’s easiest if you first moisten the scabs. Just be sure to dry the horse off thoroughly when you’re finished.

In the most severe cases, antibiotics can be employed to help eradicate the organisms causing rain rot. It might be necessary to also administer immune-boosting drugs at the same time. Of course, your veterinarian will be able to better guide you in this.

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Conclusion

Rain rot is a very common skin infection for horses. It’s not very painful or irritating for your horse and it’s not life-threatening. However, secondary bacterial infection is a very real possibility, which can lead to worsening health concerns such as strep or staph. While some horses can cure the infection when shedding their winter coat, it’s best to get a jump start on the infection as soon as you notice it starting. A simple antibacterial shampoo will likely cure your horse’s infection, but antibiotics might be necessary in extreme cases.

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Featured Image: Nihat Boy, Shutterstock

Dean Eby

An avid outdoorsman, Dean spends much of his time adventuring through the diverse terrain of the southwest United States with his closest companion, his dog, Gohan.  He gains experience on a full-time journey of exploration. For Dean, few passions lie closer to his heart than learning.  An apt researcher and reader, he loves to investigate interesting topics such as history, economics, relationships, pets, politics, and more.