Dr. Leslie Easterwood, 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 are 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 be a nuisance to a horse because the horse tries to swat and get away from them. Other than annoying the horse, the biting flies can cause physical irritations. Often, the flies congregate around the horse’s face trying drink the fluid at the corner of the horse’s eyes. Since flies carry bacteria on their feet, when they are looking for moisture they deposit bacteria, larvae, and parasites on the horse’s face and around the eyes.
“The biggest thing is the transfer (of bacteria) and all flies can be bothersome,” Easterwood said.
Flies often deposit Habronema larvae on open wounds and the horse’s eyes.
“As the larvae migrate through the tissue, they cause open sores and that is very common in horses this time of year,” Easterwood said.
Horse flies are even worse than normal house and stable flies. Easterwood said these 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.
Easterwood said these irritations, sores, diseases, and transfer of bacteria are the main reason it is important to have proper fly control.
“Good fly control extends to the face, not just spraying the body, but using stuff safe to use by their eyes,” she said.
Easterwood recommended using sprays and ointments to repel flies. Ointment can be applied to a cloth and used to wipe the horse’s eyes. The repellent may bought over the counter or through a veterinarian. Different environmental factors determine which product should be used for individual needs.