10/11/2026
๐ชฐ ๐๐ฅ๐ข๐ ๐๐๐ฌ ๐ง๐ข ๐ฆ๐ง๐ข๐ ๐๐๐: ๐ง๐๐ ๐๐๐๐ ๐๐ฌ๐๐๐ ๐ข๐ ๐๐ค๐จ๐๐ก๐ ๐๐ข๐ง๐ฆ!
Ever notice those tiny yellow or cream-colored eggs stuck to your horseโs legs? Those arenโt just dirt or debris โ theyโre likely bot fly eggs!
The life cycle of the equine bot fly (Gasterophilus spp.) is fascinating (and a little gross)! ๐คข
๐ฅ ๐ฆ๐ง๐๐ฃ ๐ญ: ๐ง๐๐ ๐๐๐๐ฆ
Adult female bot flies lay their eggs on a horseโs hair, commonly along the front legs, shoulders, and chest. A single female can lay hundreds of eggs!
๐ด ๐ฆ๐ง๐๐ฃ ๐ฎ: ๐ง๐๐ ๐๐ง๐๐ & ๐๐๐๐
As the fly approaches to deposit eggs, horses may stomp, kick, swish their tails, or run to escape the irritating fly. With the common horse bot fly, warmth and moisture from the horse licking or grooming stimulate the eggs to hatch.
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๐ฆ๐ง๐๐ฃ ๐ฏ: ๐๐ก๐ง๐ข ๐ง๐๐ ๐ ๐ข๐จ๐ง๐
Tiny larvae emerge from the eggs and enter the horseโs mouth during grooming. They burrow into tissues of the tongue and gums, where they develop for several weeks.
๐ฉบ ๐ฆ๐ง๐๐ฃ ๐ฐ: ๐๐ข๐ช๐ก ๐ง๐ข ๐ง๐๐ ๐ฆ๐ง๐ข๐ ๐๐๐
The larvae are eventually swallowed and attach to the lining of the stomach, where they remain for approximately 8โ10 months! Large numbers can cause irritation and inflammation, although many infected horses show no obvious symptoms.
๐ฉ ๐ฆ๐ง๐๐ฃ ๐ฑ: ๐๐๐๐ ๐ง๐ข ๐ง๐๐ ๐๐ฅ๐ข๐จ๐ก๐
When mature, the larvae detach, pass through the digestive tract, and exit in the horseโs manure. They burrow into the soil and develop into pupae.
๐ชฐ ๐ฆ๐ง๐๐ฃ ๐ฒ: ๐ง๐๐ ๐๐ฌ๐๐๐ ๐ฅ๐๐ฃ๐๐๐ง๐ฆ!
Adult bot flies emerge from the soil, mate, and begin laying eggs on horses again!
โณ ๐๐๐ ๐๐๐ฅ๐๐ฃ๐ ๐๐๐๐ ๐๐ช๐๐๐ ๐ฅ๐ช๐ก๐๐๐๐๐๐ช ๐ฅ๐๐๐๐ค ๐๐๐ ๐ฆ๐ฅ ๐โ๐ผ ๐๐ผ๐ธโ!
HOW CAN YOU HELP PREVENT BOTS?
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Regularly remove bot eggs from your horseโs hair using a bot knife or grooming tool.
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Discuss appropriate deworming protocols with your veterinarian. Ivermectin and moxidectin are effective against equine bot larvae.
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Be especially mindful during late summer and fall when bot flies are active.
Pine Ridge Equine Hospital
๐ 918-827-8000
