Ask Horse Journal: Mare Plagued by Flies

What do you do with a horse who has heat intolerance and is terribly plagued by flies’ SHe’s turned out with 10 other horses, and they aren?t bothered like she is.

She’s 23 years old. She seems to do OK finding shade, water, etc., but she just hangs out at the water tank with clearly increased respiration. She stands still when I pour water on her head, legs, and body, but I can’t really tell you if she sweats or not because sHe’s retired. The other retired horses in the field don’t sweat either.? She perks up in the evening and trots around when the others do and is holding her weight OK.

But she’s plagued by flies. I’m talking lower legs covered with flies. The belly, shoulders, etc. not as bad as the legs, but clearly worse than other horses. And the flies hold on and bite. I can wash one leg, and before I’ve moved to the other leg, they’re on her. This morning I fly sprayed her legs well and tonight she’s covered again, like bees on a hive covered. She doesn’t even try to stomp her front legs, but they wouldn’t leave if she did. I bring her in as often as possible and give her frequent baths. What else can I do’

Contributing Veterinary Editor Grant Miller VMD responds: Keeping horses cool in high heat can be a labor of love.? Heat itself isn?t as much of a concern for veterinarians as is humidity.

At high humidity levels, horses are unable to cool themselves through sweating and evaporative cooling because the air is so heavy with moisture that the gradient between the body surface and the surrounding air is not able to support evaporation. Therefore, it is very important to know and monitor the Heat Index in your area- this takes into account both the temperature (in Fahrenheit) and the humidity (also called the dew point).? Most veterinarians agree that heat indices above 170 are dangerous for horses to be working in and that ones above 180 are a general threat to well-being even at rest.

You are right on to dump some cool water over the horse, since that will assist in removing heat from the body.? Generally, the “rinse and repeat” method is recommended.? Besides access to shade and plenty of cool water, other options include large fans, or better yet, fans with misting systems attached.? There are all sorts of misting fans marketed for the horse world.

As for the flies, the use of the creamy ointment SWAT or the whole-horse spot-on fly treatment War Paint may be helpful.?Be sure you try switching fly sprays.?Some fly sprays that have lanolin or oil in them tend to stick better and stay active longer, versus ones that dry up and disappear after 45 minutes.

For the lower limbs, you may find that fly wraps (available at most catalog stores) are useful.?they’re mesh net Velcro-closure wraps that cover the leg from mid-cannon down.? Many folks soak them in a fly repellent containing DEET and then put them on the legs.? Overall, it sounds like it is time to get more aggressive with the flies.

See also our article on the best fly products. One of your most cost-effective fly-control options is fly parasites. Most facilities report a huge decrease in the amount of fly spray they need to buy (and you should reduce fly spray in order to not kill the predators too!). With proper use the fly population will lessen greatly. The time to start parasites is in the early spring.

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