The following was in response to various ULish stories about maggots infesting people. The following is a summary. Facultative myiasis refers to infestations where the maggot is normally free-living, but adapts itself to a parasitic existence under certain circumstances. Wounds may become invaded by carrion flies, and occasionally urinary tract infestations are recorded. Occasionally, maggots do make their way into the intestinal tract of humans and survive long enough to cause severe clinical symptoms.
Obligatory myiasis involves flies that are dependent on an animal host.
The screw-worm, Cochliomyia hominivorax, is one of the best known to Merkins, and is the most important producer of human and animal myiasis in the western hemisphere. The fly deposits eggs in wounds and the resulting maggots feed in the surrounding tissue. One particularly unpleasant example was recorded from Kansas in the 1880s. A man received a deposit of eggs in his nose while he slept. Apparently the flies were attracted to a nasal discharge.