Ms-MR-1-Insects and allergies18by Marilyn Munzert
Every April, a Quarter Horse named Bellboy, started getting insect bites along the midline of his belly, and the bites began festering and oozing. As the sores got worse, so did Bellboy’s attitude.
According to Dr. Anthony Yu, a veterinarian at Ontario’s University of Guelph who specializes in dermatology, the source of Bellboy’s misery is most likely midges, also known as gnats or no-see-ums.
The bugs, tiny as they are, have the muscle to turn a normally laid-back horse into a crank who tries to bite everyone who comes near him.
Dr. Yu says insect bite sensitivity is one of the most common allergies our equine friends suffer from, and midges are the primary culprit. Sores along the horse’s midline, as well as the spring and fall timeline, are the primary indicators of midge sensitivity.
The first line of treatment would be aggressive systemic steroid treatment and the use of a fly spray with a high percentage of permethrin, Dr. Yu advises. And because the permethrin adheres tightly to the hair coat, horses may need to be sprayed only once a week (or more or less, depending on regional variances).
A fly sheet with a belly band is also recommended, and it can by sprayed with the permethrin spray, much like the Army does with some military clothing to prevent insect bites.
Putting box fans in the horse’s stall, creating a constant air flow, decreases the chance of the gnats actually landing on the horse. It is especially important to keep the horse inside in front of the fan during the dusk and dawn hours, when the midges tend to be most active.
According to Dr. Yu, Quarter Horses are among the breeds of horses predisposed to insect hypersensitivity. And many horses have combination allergies — sensitivities to insects, food, drugs or allergens in their environment like dust, mold or pollen. They may suffer symptoms that range from itching and hives to asthma or chronic obstructive pulmonary disease.
To identify which triggers are setting a horse off, horses can undergo skin tests, or owners can simply try to reduce or avoid all allergens by moving from the current environment. An example would be stabling a horse with pollen allergies or turning out a horse with dust or mold spore allergies. The horse might need to live in a different barn — a run-in instead of a stall, or a barn on top of a hill instead of one in a low basin with stagnant water and evergreens that attract midges. On the other extreme, this might mean that a horse needs to live in a different part of the country, to get away from a certain type of insect or pollen.
Consider using rubber mats and low dust bedding, such as recycled cardboard or coarse-chip shavings to minimize dust exposure. In the feed, use pelleted rations or soaked feeds and wet down hay before feeding it.
Techniques to control insects could be to move horses away from standing water, manure piles, compost and cattle; avoid dusk and dawn turnout; and use fly sheets and masks sprayed with permethrin, install fine insect mesh around the stalls, box fans, time-release insecticides, fly wasps and fish in ponds to cut down the number of insects.
Use dietary trials to diagnose food hypersensitivity or intolerance, possibly switching to novel food ingredients, such as different hay from another region of the country, and simple grains such as oats.  Avoid mixed feeds like sweet feed and alfalfa — molasses-based treats, supplements and feeds. Stay on this regimen until the allergy symptoms have dissipated.
Owners may also want to shampoo their itchy horse regularly. Using chilly water in the bath, will constrict blood vessels, which decreases the delivery of inflammatory agents to the skin. The use of medicated shampoo can help treat any sores that have become infected.
Depending on the severity of the symptoms, corticosteroids may be used for a period of 3-7 days to eliminate the cause of the inflammation. The supplement MSM is frequently used as an anti-inflammatory/antioxidant that helps calm itchy skin. Omega-3 fatty acids, like flax seed and fish oil help keep inflammation in check, whereas omega-6 fatty acids found in safflower oil and canola oil, as well as other sources, improve skin and coat condition and help prevent the percufaneous absorption of allergens.
Allergies are a manageable condition, provided that owners are willing to do what it takes.