The adult horse botfly is a brown, hairy fly with only one pair of wings and measures about 2 centimeters in size. During the summer months, horse botflies—which strongly resemble bees—can often be seen and heard buzzing around horses and donkeys. Horse botflies are sometimes mistaken for horseflies.
Female botflies lay their yellow eggs on the forelegs of the donkey. Each fly lays about 1,000 eggs. The donkey licks up these eggs. Larvae hatch from the eggs in the mouth and penetrate the mucous membranes. After staying for several weeks, the larvae move to the stomach, where they attach themselves to the stomach wall. They remain there throughout the winter.
In late spring, the larvae detach from the stomach wall and leave the body via the manure. The larvae then burrow into the soil, and after several molts, the adult fly emerges and the cycle starts again.
Botfly larvae cannot be detected through manure testing because botflies lay their eggs on the outside of the donkey. That’s why we advise always deworming preventively once a year after the first frost. The first frost kills off the free-living botflies, eliminating the risk of reinfection after treatment.
As a Worm&Co customer, you will receive an email from us advising you on the best time to administer the end-of-year treatment.
Donkeys carrying an infestation can become seriously ill. Symptoms include inflammation of the mouth and tongue, stomach inflammation in the form of gastric ulcers, and a reduced appetite leading to weight loss and lethargy. Severe infestations may also cause anemia, loose stools, and in the worst cases, colic.
It is important to prevent an infestation, or at least minimize the risk as much as possible. To achieve this, the eggs should be removed so that the donkey cannot lick them up. Special blades and grooming blocks are available for this purpose from, among others, our partner Horsefitshop. If you are unable to remove the eggs, you can wash the donkey with lukewarm water mixed with vinegar. This makes it easier to remove the eggs.
We recommend treating once a year, but there are also situations where you may choose not to treat preventively. For example, this may be the case for donkeys that have carried few or no eggs, or donkeys that have already been treated during a certain period. The most important thing is to use common sense and to closely monitor your donkey's health.
Feel free to contact us if you have questions about botfly larvae. We are happy to provide you with personalized advice and think along with you!
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