Gasterophilus haemorrhoidalis

Gasterophilus haemorrhoidalis (also called nose bot) is a species of the genus Gasterophilus that lays eggs on the lips and around the mouth of horses, mules and donkey, but also reindeer.

In equidae, third-stage larvae attach to the stomach, but also to rectum, sometimes in great numbers.  Heavy infestation can cause anal prolapse in foals and mules.

In reindeer, the larvae grow in the sinuses and throat of the host animal, and are sneezed out in the spring.

They do not parasitise humans.