Protect Your Horse from Summer Sores and Fly Discomforts

Flies blanketing a horse's face.
Flies blanketing a horse's face. Carien Schippers

Newsdate: Monday, June 1, 2020 – 11:30 am
Location: PARSIPPANY, New Jersey

Flies are a nuisance in the house, but the dangers they pose in the barn can become dangerous and expensive. Beyond increasing the risk of strangles and pigeon fever, flies can produce time-consuming and costly summer sores — chronic, nonhealing wounds that often rapidly progress and enlarge.

Summer sores resulting in proud flesh on horse's leg.

Summer sores resulting in proud flesh on horse's leg

If summer sores are untreated and proud flesh becomes prominent, horses will lose riding and training time and could be out for months.
© 2019 by Zoetis

This frustrating condition frequently makes horses unable to ride or compete, and medical treatment can be extensive or even require surgical care.

“Two stomach worm species, specifically Habronema and Draschia, cause summer sores,” said Dr. Amy Poulin, Equine Technical Services veterinarian with Zoetis. “And when Habronema and houseflies are present, it’s a potential problem for any horse in a warm, humid climate.”

“When infective Habronema larvae are shed in horse feces, house flies can later pick up the larvae and deposit it into open wounds as well as the mouth, lip, eye and groin areas of horses. The inflammatory reaction results in summer sores,” Dr. Poulin said. “If fly larvae develop in manure infected with Habronema larvae, any horse within the fly’s quarter-mile migration radius becomes at risk for infection.”

Losing Precious Time in the Saddle

Summer sores are so prevalent in southern Florida that they are infamously referred to as “Florida sores,” said Anne-Marie Morgan, a horse owner and head trainer with Miami Equestrian Club. Their impact reaches across the Southern states, often severely. Morgan has witnessed fleshy summer sores as large as softballs plague horses for six months.

“If summer sores are untreated and proud flesh becomes prominent, horses will lose riding and training time and could be out for months,” Morgan said. “They are extremely irritating and itchy for the horse and cause frustration for riders and trainers.”

When Morgan’s horse developed a summer sore, Morgan spent more than $120 per month for gauze, elastic adhesive, saline solution and topical treatments. That doesn’t include what she spent on fly spray and protective equipment, such as fly boots, sheets and masks, to help protect horses from scrapes and fly contact.

Preventing a Costly, Career-impacting Expense

While protective fly gear may help, there are more convenient and consistent solutions available. “Products that kill fly eggs before they are hatched are great assets to fighting flies in both large-scale and smaller barns,” Morgan said.

Dr. Poulin recommends including Solitude® IGR, a pelleted feed-through fly preventive, as part of the daily ration to help reduce fly burdens. Solitude IGR contains cyromazine, an insect growth regulator that dramatically reduces the number of house and stable flies by preventing immature flies in the manure from developing into adults. As existing adult flies die off, the overall fly population is significantly reduced within four to six weeks.

In studies, Solitude IGR was up to 100% effective in preventing house and stable flies from reaching adulthood.1,2 This feed-through product works best when added to horses’ daily ration prior to the start of fly season and when fed to all horses on the property, because it works by halting the development of fly larvae in manure.

“The active ingredient in Solitude IGR — cyromazine — is an insect growth regulator, meaning it inhibits housefly larvae from developing into adults,” Dr. Poulin said. “Solitude IGR helps stop the vicious cycle. It is a valuable addition to any equine fly management program to increase comfort and decrease the spread of diseases and infections caused by flies.”

Dr. Poulin also recommends deworming with Quest® Gel to treat and control Habronema for reduced summer sore risk.

Work with your veterinarian to develop a summer sores prevention program that includes a fly preventive and deworming program. Visit to learn more.

Do not use Quest Gel in foals less than 6 months of age or in sick, debilitated and underweight horses. Do not use in other animal species, as severe adverse reactions, including fatalities in dogs, may result.

Press release provided by Zoetis

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