Myiasis is the invasion of organs and tissues of humans or other vertebrate animals by fly larvae, which at least for some time feed on the living or dead tissues or, in the case of intestinal myiasis, on the host’s ingested food.

Types of myiasis

Myiasis may be accidental, obligatory or facultative.

Accidental myiasis usually involves eating food that is contaminated by eggs or larvae of flies that are not parasitic in mammals, such as house flies. Although the larvae may survive for some time in the intestine, no flies are specially adapted to cause intestinal myiasis in humans. (In contrast, obligatory intestinal myiasis occurs in other mammals.) The presence of larvae in the human intestine may nevertheless cause considerable discomfort, abdominal pain and diarrhoea, which may be accompanied by discharge of blood and vomiting. Living larvae may be passed in excreta or vomit.

In obligatory myiasis it is essential for the fly maggots (larvae) to live on a live host for at least a part of their life. For example, larvae of Cordylobia anthropophaga, Cochliomyia hominivorax, Chrysomya bezziana, Dermatobia hominis and Wohlfahrtia magnifica are all obligatory parasites of humans and other vertebrates.