The term myiasis means the invasion of the tissues or organs of animals, including man, by the larvae of flies. There are a number of species of flies that will invade living animals, even to the most specialized and parasitical types.
These types are, first, Oestridae (bots, warbles). The bots or warbles have under certain cases become highly specialized. The ox warbles (Hyperma lineata) confines itself to one host, the relationship being so close that if it should be removed prior to normal maturity it will die. Most authorities believe that the entrance is through the esophagus to the back. The sheep bots (Estrisovis) attack primarily animals, as do also the horse bots, but cases are on record in which man has been infected. The eggs are deposited in the mouth or nasal passages, the larvae transferring their location to the sinuses, the base of the tongue or the orbit