Bot flies may not seem to be quite the pests that mosquitoes, gnats and chiggers are, but don't tell that to your horses. Any horsekeeper will tell you that bot flies can easily make their lives and their horses miserable.
Preventing and eliminating bot eggs takes work, but the efforts will pay off in fewer flies and better health for your horses. Daily maintenance is the key. A few minutes a day can prevent a lot of trouble and expense later.
Prevention is Best
The best way to cure an outbreak of bot flies is to prevent one. It's best to know what you're dealing with first.
Where the Bot Flies Meet
During warm months, bot flies lay eggs on the undersides and legs of horses. These tiny, yellow-white eggs itch and annoy horses and cause them to nuzzle and lick irritated areas. Eggs not ingested sometimes develop into larvae that burrow into a horse's skin.
Once ingested, eggs hatch and spawn parasites that become larvae in the intestinal system. These larvae siphon nutrients from the animal. The following spring, larvae exit the horse through his manure.
Bot fly ingestion can cause gastrointestinal discomfort in horses, but most horses do not show any clinical signs of illness. It typically takes a large infestation of 50 or more to cause obvious symptoms. Most horses will have far fewer bots in their system.
A bot infection can cause some serious problems. Ulcers, weight loss and colic are rare but real possibilities. Seek veterinary care if you believe your horse has a bot infection.
An early warning sign that bots will try laying eggs is a frustrated horse. Buzzing flies annoy horses, causing them to stomp or act out.
Equine Insect Spray
Prevention begins with equine insect spray, which will deter female bots from landing on a horse. Just remember, horses sweat a lot in hot weather, when bots are active and sweat dilutes the spray. You need to spray your horses daily, at minimum.
Fly sheets wrap around horses and protect their undersides, where bots like to spawn. Fly socks, or fly boots, deter bots from their preferred landing areas, the legs. You also can use a mesh hood that leaves the mouth and ears free, but prevents horses from ingesting bot eggs.
Avoid applying baby oil to your horses. This old-school home remedy does not deter bots and will suck up dirt and grime.
When Deterrence Fails
Nothing will keep all the bots away. Even with a good spray and protective clothing, you must inspect your horses daily and remove any eggs you find. Fortunately, bot eggs are usually easy to see, particularly on dark horses.
Warm water mixed with insecticide usually washes away attached eggs. It also kills larvae in those eggs that survive.
Bot Knives Yes, Razors No
Bot knives safely and efficiently scrape eggs off your horse. Do not try to scrape away eggs with a razor or sharp knife, however. Unless you're highly skilled, you could injure the animal. If you're not experienced with a bot knife, seek veterinary counsel.
The surest way to kill ingested larvae is regular deworming treatment. The best early stage bot larva killer is ivermectin, which can be found in many horse worm medications.
If you wait more than a month after the end of bot season to begin deworming treatment, choose a medication containing moxidectin, which targets later-stage bot larvae.
However, know that moxidectin does not work on all species of horse bots, so deworming treatments are best begun in the spring, when bots first show up.