Page 78 - Speedhorse December 2019

Ringworm, or dermatophytosis, is a fungal organism that lives on skin and can spread to humans and other animals. Signs include patchy hair loss, typically on the trunk, head and neck, and the hair can easily be pulled out in tufts around the edges of the hairless area.
RINGWORM
“This is another common infectious condition,” says Evans. “The medical term
is dermatophytosis; the fungal organism is
a dermatophyte that lives on skin. There
are a number of fungal organisms that can
cause ringworm. Most of them can affect all species and not just horses. When a horse has ringworm, it could be spread to humans and other animals. I encourage horse owners to be careful and use gloves when handling or treating the horse. If their immune system is suppressed for any reason (stress, chemotherapy, etc.), they would be more likely to get it themselves.
“We typically see ringworm in a random distribution. It is not as dependent on weather or management. The horse may have a suppressed immune system for some reason and this allows the fungal organism to become established. Signs are patchy hair loss—anywhere on the body, but typically on the trunk, head and neck. We don’t see lesions as often on the limbs.
“One of the characteristic signs, if you examine around the margins of where the hair is lost, is that you can easily pluck the hair. It readily comes out in tufts around the edges
of the hairless area. This is different from
a typical rub mark that some people might think is ringworm. If I tug on the hair around the margins, and it comes out in tufts, I am suspicious of fungal infection.
“Diagnosis can be made with a skin scraping, or even a plucking of the free hair. It is easy to see fungal elements on a microscope slide. Sometimes I biopsy a lesion, depending on how aggressive it is. Some horses are itchy with ringworm and some are not,” Evans says.
Humans may play a role in transmission
by using the same tack and grooming tools
on different horses, or by not being careful about bio-security issues. “It can spread rapidly amongst a group of horses if people aren’t careful when handling an infected horse,” he explains.
Ringworm can heal spontaneously in one to six months, especially if the horse is outdoors in the sunlight—which is one reason it’s not
as common in summer as in winter, but some horse owners choose to treat it. “If it occurs in a group of weanlings out in a pasture, you might just let it run its course,” he says.
To treat ringworm, he recommends bathing the horse using a horse shampoo. “Rinse the horse well, and while he is still wet, apply a lime-sulfur mixture. There are also commercial products available. Most of them are made for small animals, but the two key ingredients (lime and sulfur) also work for ringworm on horses,” says Evans.
“I have the client sponge the mixture onto the affected areas, let it sit for half an hour, and then rinse the horse off really well. If the condition does not resolve within a week, I have them repeat the treatment. Only rarely do I need to examine a horse again after
two treatments.”
Some people use diluted bleach to treat ringworm. “I haven’t used it myself because I’ve had good luck with the lime-sulfur, and bleach seems like it would be a bit caustic,” he says. “If you don’t get the dilution correct, you might end up burning the horse’s skin or yours, or stain your clothes. Sulfur smells bad but it’s not as harsh as bleach.”
URTICARIA (HIVES)
Hypersensitivity reactions may produce hives or welts in the skin. This may happen at any time of year, depending on what the horse is exposed to. “The horse may break out in hives for unknown reasons. The client is often concerned about allergies, but often it’s more of a hypersensitivity to something the horse has come into contact with. As an example, a harsh detergent used on the horse’s blanket, or new hay, or new load of shavings that’s come
into the barn (for bedding) that has a different chemical treatment,” says Evans.
Occasionally, a certain horse is reacting to the adjuvant in a particular vaccine or has a drug sensitivity. “The owner may have tried
a new joint supplement and the horse reacts,” says Evans. “The history is very important in these situations, to see what the horse has been exposed to. Have there been feed changes, new bedding material, medications given, topical sprays or any other things that might explain why this horse may have suddenly become sensitive?
“I encourage clients to make incremental changes in the horse’s management to see if the horse improves. Commonly the problem is due to contact with something, or an environmental allergen. Food allergies are rare in horses, but do exist.
“The hives may be patchy over the neck and shoulders, or over the whole body. In
an acute case, we give the horse a little bit
of antihistamine and steroids to try and decrease the reaction. Once we have it under control, we wean the horse off the steroids and ask the client to make small changes to the management of that horse to see if they can identify the cause of the problem—if
we haven’t been able to figure it out from
the history. We ask the client to remove one variable at a time and note when the problem goes away, doing a process of elimination, if possible. Then if we can identify what the causative situation is, we remove that from the horse’s environment or management.”
There are some reactions, however, that may occur only once in a certain season and you are guessing at the diagnosis, thinking it may have been some sort of insect attack or a spider bite that caused a rapid and acute response. “Unless the same insect bites the horse again, it may never happen again.”
74 SPEEDHORSE, December 2019
Urticaria, or hives/welts, is a hypersensitivity reaction and can appear any time of the year. Hives can occur because of an environmental allergen, such something new the horse has come into contact with, or a drug/vaccine sensitivity.
EQUINE HEALTH