Protect Horses Against Flies and Related Health Problems

If you are around horses or a stable lately, you might have noticed an increase in the number of flies pestering nearly everything that moves. Leslie Easterwood, DVM, clinical assistant professor for the large animal clinical sciences department at Texas A&M University College of Veterinary Medicine & Biomedical Sciences, said flies are worse in the summertime and this year they they seem particularly bad.

"Last year it was dry and hot so it didn't seem quite as bad, but this year we've had rain and the temperatures haven't been as high so there seems to be an increase," Easterwood said.

Flies can cause a number of physical problems for horses. Often, the flies congregate around the horse's face and try to drink the fluid at the corner of the horse's eyes. Since flies often carry bacteria on their feet, they have the potential to deposit bacteria, larvae, and parasites on the horse's face and around the eyes. Easterwood said that flies often deposit Habronema larvae on open wounds and the horse's eyes.

"As the larvae migrate through the tissue, they (can) cause open sores and that is very common in horses this time of year," Easterwood said.

Easterwood said these horse flies are at least 10 times the size of a house fly, have big mouths, and transfer more diseases than a house or stable fly.

"They can transfer diseases such equine infectious anemia, a very fatal disease that we don't have a cure for," she said.

Easterwood said that to mitigate the risk of irritations, sores, diseases, and transfer of bacteria, horse owners should employ proper fly control.

Easterwood recommended using sprays and ointments to repel flies. "If there is a bad fly problem, you would be better off to use a product every day that you can reapply frequently to keep the population down," Easterwood said, adding that most caretakers apply fly products to horses daily.

She warned, however, that many products claim the repellent lasts longer than others: "We have found that very few [products] last as long as they say they will," Easterwood said.

She also suggested covering the horse with fly sheets for their bodies and fly masks for their faces.

Other options include an automatic fly spray system in barns, moving manure and trash piles away from the horses, drying out the manure pile, or the use of fly predators.

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