We are currently receiving many questions from horse owners about when we recommend treating for botfly larvae and whether treatment is always necessary. In this article, we’ll walk you through the do’s and don’ts of dealing with botflies.
We want to emphasize that there is no reason to panic. Many videos are being shared that might make you afraid this could happen to your horse too. We understand the emotion, but we hope to ease some of that fear.
Don’t forget that usually only the extreme videos are shared. The horses that stay healthy all year round are not shown. We find it very important to inform horse owners so that, if a horse does show symptoms, timely treatment can prevent more serious issues.
Meet the Botfly
What does a botfly look like?
The adult botfly is a brown, hairy fly with only one pair of wings and measures around 2 cm. In summer, we often see and hear them buzzing around horses, resembling bees. Botflies are often confused with horseflies.
How does an infestation occur?
Female botflies lay their yellow eggs on the horse’s forelegs. Each fly lays around 1,000 eggs. The horse licks them up, and the larvae hatch in the mouth and penetrate the mucous membranes. After a few weeks, the larvae migrate to the stomach, attach to the stomach wall, and stay there over winter.
In late spring, the larvae detach from the stomach wall and leave the body through the manure. They burrow into the soil, go through several molts, and eventually emerge as adult flies, starting the cycle anew.
Can botfly eggs be found in a manure test?
No, botfly eggs cannot be found in manure because they are laid on the outside of the horse. That’s why we recommend deworming preventively once a year, specifically AFTER the first frost. Are you a Worm&Co customer? Then relax — we’ll email you when it’s time to give the end-of-year treatment.
Why treat only after the first frost?
Because frost kills free-living botflies, the risk of reinfection after treatment is gone.
Symptoms of botfly larvae
Horses carrying an infestation can become seriously ill. Symptoms include inflammation in the mouth, tongue, and stomach (ulcers), reduced appetite leading to weight loss and lethargy. In severe cases, anemia, diarrhea, and colic may occur.
Preventing infestation
How can you prevent or minimize an infestation? It is important to remove the eggs so the horse cannot lick them up. Special knives and blocks are available (Horsefitshop). If that doesn’t work, you can wash the horse with lukewarm water and vinegar to help loosen the eggs.
Do I need to treat for botfly larvae every year?
We advise treating once a year, but there are cases where a preventive treatment may not be necessary. For example, if a horse has carried few to no eggs or has already been treated during a specific period. Common sense and monitoring your horse's health are key.
If you have any questions, please feel free to contact us!
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