07/06/2026
🪰 Let’s Talk Bot Flies 🪰
Bots aren’t horse worms but rather flying insects, similar to a scrawny wasp, whose life cycle is inextricably linked with the horse. How do we know if horses have been affected & how do we treat? Keep reading below to find out! ⬇️
Larval Stage: These tiny motile larvae stay in the mouth for 3-4 weeks, emerging to make their way slowly down the gastro intestinal tract to burrow into the gut wall. Here the larvae remain for around 10-12 months, feeding off the horse’s gut till they mature in spring or early summer where they then detach and pass through the hosts manure.
Pupal Stage: The bot larvae pupate in the soil for 3-5 weeks, after which the adult bot fly emerges!
Adult Fly: Once hatched the adult flies survive long enough to mate and lay their eggs on the horse which are small pale coloured eggs that stick to the hair shafts where they survive for 7-14 days 🥚 . Adult flies die once nutrients remaining from their larval stage are used, usually in around 2 weeks.
Now - the big question - how do we treat? 🧐
Flies 🪰: Insect repellants to repel the adult bot fly from laying eggs, although this won’t deter them entirely.
Eggs 🥚: Once eggs are laid on the coat, these can be scraped off the hairs using a bot knife to minimise infection.
Larvae: Ingested larvae aren’t treatable until they’re in the stomach of the horse. Veterinary guidance is to target them with a single treatment, specifically waiting until the first frost/cold snap of the winter which will kill bot flies and ensure no more reinfection.
Ivermectin & Moxidectin are both active ingredients found in horse wormers that are affective and you could even choose to combine this with your winter worming dose 🪱
