Beat the Bots: How to Get Rid of Botflies

| August 15, 2011 | 2 Comments

If you’re a horse owner, Spring and Summer are probably your favorite seasons. However, with warmer weather comes bot flies, and every horse owner knows these pests can cause trouble! But what kind of trouble, exactly?

A basic overview of bots goes like this:

1. Bot flies lay their small, yellow eggs on the horses legs and undersides in summer.

2. The horses legs and underside feel itchy, so the horse will nuzzle and lick at the eggs, ingesting them. (Larvae that is not ingested can also hatch and crawl inside the skin, causing irritation and in some cases, infection.)

3. Next spring, the eggs will have turned into larvae, and will be passed through in manure – but not before robbing your horse of essential nutrients. Bot larvae can also cause stomach ulcers and, in serious cases, colic.

Female equine botflies must reach a horse to procreate, so nothing short of death will stop her from getting there. This is extremely frustrating for the horse, which is why the first sign you will often receive of a botfly buzzing around will be your horse stamping his feet, swishing his tail, and perhaps becoming slightly agitated.

So what do you do?

The golden rule of horsemanship – prevention is better than cure! While you will never completely prevent bot flies from laying on your horse, there are ways to lessen the risk.

  • Use an equine insect spray. These generally deter most insects that bug your horse, especially during summer, and are a good base to start from. Keep in mind that horse sweat will dilute insecticides and sprays, so spraying your horse daily is the minimum requirement.
  • Use a fly sheet. While the bots lay their eggs predominantly on the legs of the horse, a fly sheet will lessen the likelihood of them laying on your horses underbelly.
  • Use a pair of fly boots or socks on your horse. There are several of these available on the market, such as Summer Whinnys.
  • A common household remedy is to coat your horses legs in baby oil, making it difficult for the flies and eggs to grip to your horses coat. This isn’t a surefire prevention though, and doesn’t deter anything – in fact, it will attract a lot of dirt and dust to your previously clean horse!

Remove the eggs daily – this will lessen the chance of your horse ingesting them.

  • Warm water with some insecticide in it can encourage the eggs to detach and hatch, while the insecticide kills the larvae.
  • Bot knives are cheap, easy to use, and effective. Bot eggs are almost impossible to remove with simply your fingers, and a bot knife is a safe way of removing them without hurting your horse.
  • Household remedies include using sandpaper and cheap razors to remove the eggs, but these methods can be painful and dangerous to both you and your horse if not used correctly and carefully.

Finally, ensure your horses worming schedule is up to date.

  • Your horse should be wormed in the Autumn/Spring months, about one month after the bot fly season has ended, with a worming paste that includes Ivermectin. This will ensure the larvae is killed in the early stages of its cycle.
  • However, if you worm your horse later than one month after the botfly season has ended, look for a worming medication with Moxidectin – this is most effective against the later stages of common bot fly larvae, however, is not effective against all species of horse bots.

Above all, bot flies require persistence and daily management. Taking a few minutes out of your day to rid your horse of these pesky pests will save your horse and your wallet a lot of misery!

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Category: Health & Care

About the Author ()

Ellie is an Australian university student studying Public Relations & Organisational Communication. Her horse, Felix, has been stealing her carrot cake for 11 years, & when she's not pampering him, she can be found eating sushi, vaulting, or trying to plan the unplannable. You can get to know Ellie here.
  • Geoff Tucker, DVM

    Since the introduction of ivermectin dewormer the observation of bot eggs attached to the legs has virtually disappeared in the areas I practice (the east coast of the US).

    Remember, the yellow eggs seen on your horse’s legs may have already hatched and you work in removing them is in vain.

    A few interesting facts about bots:
    1) it is the warm and moist breath of the horse that causes them to hatch and jump into the mouth.
    2) There are two major species of bots. One lays their eggs in a certain area of the horse while the other lays them in a different area. One migrates along the tongue to the larynx before they emerge and are swallowed while the other migrated along the gums. One attaches to the lining of the stomach above the margo plicatus (the non-glandular section) and the other below it (the glandular section).
    3) The bot fly dies after laying their eggs.
    4) The increasing daylight of spring causes the attached larva to dislodge and exit the horse where they develop into the fly – the cycle repeats.
    5) The larvae do not migrate through the horse like other internal parasites (large and small strongyles, ascarids). they just winter in the warmth of the stomach.
    6) Giving a boticide (ivermectin) doesn’t kill them. It causes them to release their hold in the stomach, pass through the horse, and fall to the ground where the cold kills them. That’s why deworming for bots should always be done in the late fall in climates where it is cold in winter. I’m not sure, but I don’t believe bot flies exist in the tropics.

    Doc T

  • Patricia Reszetylo

    I recently read an article in Outside Magazine about a guy who traversed the ENTIRE length of the Amazon (why one would want to do that I’m not sure, other than it’s there and nobody had done it). One of the problems he encountered, according to the article, was bot flies embedding themselves in his scalp. That would seem to indicate they do live in the tropics – although I’m the first to tell you I am NOT an expert on that. =)