Management of Thrush, Rainrot, and Scratches

Thrush, rainrot, and scratches are problems that most equestrians have probably encountered, but in the hot, often humid summer months, these issues can incessantly plague horses and their owners. While different in their presentation, thrush, rainrot, and scratches have a lot in common. For horse owners, there are several problems that arise due to environmental factors or predisposing conditions, but these issues can easily be prevented or treated with proper care and management.

This month, Palm Beach Equine Clinic’s Dr. Bryan Dubynsky shared his expertise on the causes, treatment, and prevention of thrush, rainrot, and scratches.

Thrush

Thrush is an infection within the horse’s hoof most commonly caused by bacteria that invade the deep clefts or grooves (known as sulci) of the frog. Fusobacterium Necrophorum is the common bacterial culprit, which naturally occurs in the environment, especially in wet, muddy, or unsanitary areas. Thrush bacteria thrive where there is a lack of oxygen.

Some horses are predisposed to developing thrush due to conformation, such as a rather high heel or deep sulci, or a narrow or contracted heel. The bacteria will manifest in horse’s feet that are not picked out regularly, or standing in muddy, wet environments, including paddocks or stalls that have not been cleaned properly. Thrush can typically be first identified by the odor. The frog will have a strong, rotten odor and become spongy. Visually, the frog can even exudate (ooze) pus.

The treatment for thrush is fairly simple as it is very sensitive to oxygen. The most important thing is to have your vet or farrier trim or debride the frog to expose affected areas to the air. It is best to keep the hoof clean and dry. Adding a common detergent to the thrush areas, such as Betadine or any commercial product (Thrush Buster, Coppertox, etc.) will help to kill the bacteria. Most importantly, if the horse is not removed from those predisposing environmental factors, treatments can be ineffective.

Maintaining a level of activity for our equine partners will increase blood flow to the feet and promote health in the area. Horses found in dry environments with ample space to move typically do not suffer from thrush. The activity of horses moving keeps the frogs healthier. The more blood flow you have in the foot, the less chance there is for infection to manifest. Thrush does not always cause lameness. In extremely rare cases, thrush can penetrate deeper and cause an infection in deeper tissue or even in the coffin bone. When in doubt, always contact your veterinarian.

Rainrot (Dermotophilus Congolensis)

Rainrot is caused by a naturally occurring bacteria named Dermotophilus, which produces spores. The condition is recognized as scabby, scaly, crusty spots on areas of the horse that have been exposed to rain. It is commonly seen on the neck or across the back (dorsum). Rainrot is not typically apparent on the legs or under the belly. A surplus of rain on the skin washes away the natural protective oils. Once the skin is stripped of the natural protective layer or any sort of trauma to the skin barrier occurs, which can be even as simple as an insect bite, the Dermotophilus spores are able to invade the deeper dermis skin layers. The spores penetrate into the deeper layers of the dermis, and the body reacts by sending white blood cells and proteins to fight the invaders.

This reactive response causes small pustules, scabs, and bumps to form. Similar to thrush, rainrot is an environmental issue. It is most commonly seen in warm areas with high humidity, excess rain, and insects. The most important prevention is to keep horses out of prolonged periods of rain. A horse can be out in the rain for short periods of a day or two, but if it is constantly in hot and rainy conditions with biting insects, more than likely the horse will develop rainrot.

Dr. Dubynsky emphasizes that topical products are not worth anything if the horse is not removed from the environmental factors. Once you remove the environmental factors, a keratolytic agent (something that exfoliates keratin), such as benzoyl peroxide or an antibacterial shampoo, will help the skin heal. He also cautions that if the horse does have scabs, you do not necessarily want to pick the scabs off because then you are leaving open skin without protection for more bacteria to invade. The most important tip to healing is to keep the area dry.

In very rare, severe cases of rainrot, it is best to contact your veterinarian to put the horse on antibiotics. If left untreated, and the horse is not removed from the environmental causative factors, the infestation can lead to Staphylococcal Folliculitis; a type of Staph bacteria that will invade the hair follicles and cause a more serious situation.

Scratches

Scratches is a generic term for many different ailments. The definition of scratches can be a bacterial, fungal, or viral dermatitis or inflammatory condition of the pastern or fetlock. It is defined as a chronic Seborrheic Dermatitis, characterized by hypertrophy and exudation on the palmar plantar surface of the pastern and fetlock.

There are certainly predisposing factors for scratches, including the same environmental factors that cause thrush or rainrot. Predisposing factors for scratches include horses that are bathed often or stand in wet conditions all the time. Horses that have an excess amount of hair on their legs, especially draft horses, may be more prone to developing scratches. This is because the hair traps dirt and moisture on the skin. Scratches can develop in horses that are bathed too often, such as the intensely managed show horse. Frequent bathing of the horse can strip away the natural protective oils and barrier of the dermis. This allows bacteria or fungi to invade. When moisture penetrates the skin, it causes an inflammatory reaction. This presents as heat, redness, pain, and loss of protection to keep bacteria out.

The most effective first step for prevention and treatment should be to eliminate environmental predisposing factors. Removing excess hair during humid months and keeping horses clean and dry to the best of your ability will reduce the probability of developing an infection. Bathing horses once a day with Betadine or antifungal/antibacterial shampoo will help to clear the infection. Be sure to leave the shampoo on for 20 minutes for all of the medicine to penetrate. Rinse thoroughly, and make sure the horse is completely dry. In order to effectively treat the bacteria, horses, especially their legs, should be completely towel- or air-dried before being returned to their stalls or paddocks.

As always, contact your veterinarian immediately if there appears to be a deeper infection present, or if you would like more detailed information on how to treat and prevent these bacterial infections. To contact your Palm Beach Equine Clinic veterinarian, call 561-793-1599 or visit www.equineclinic.com.