Cutaneous myiasis, also known as dermal myiasis, human botfly, warble fly infestation, tumbu fly infestation, and screwworm infestation, is a self-limited fly larval infestation of the skin or skin appendages. Furuncular myiasis is a common disease of the traveler returning from South America (with a high incidence of exposure and infection in Belize and Bolivia) or sub-Saharan Africa. Some countries in Central America and Mexico have reported an increase in animal and human cases of New World screwworm infestation (wound form) in 2025. As of November 2025, Mexico has seen 92 human cases. In August 2025, a US case was reported in a person returning from El Salvador. 

There are 3 cutaneous forms of disease: furuncular, wound, and migratory.

Furuncular myiasis:

• The furuncular form is caused by Dermatobia hominis and Cordylobia anthropophaga. Lesions begin as small erythematous papules, which may be single or multiple, and enlarge as the larva enlarges into furuncles with a distinct central punctum. The patient may complain of pruritus or movement or pain within the lesion. With light palpation, the clinician may be able to feel the larva move.
• Infestation occurs when ova are laid on the skin or clothing by any number of species of fly of the order Diptera. The ovum will hatch, enter human skin, and form a small papule within 24 hours of contact with skin. The lesion will enlarge as the larva grows in size. If left unattended, the larva will eventually mature and emerge on its own. Cordylobia anthropophaga (the tumbu fly, found in sub-Saharan Africa) larvae mature within 1-3 weeks, whereas D hominis (the human botfly, found in the Americas) larvae take upward of 3 months. Dermatobia hominis ova are transmitted by mosquitoes (the fly lays its eggs on the mosquito, and they are deposited on the human while the mosquito is feeding). Cordylobia anthropophaga ova are deposited on wet clothes and enter the skin when the clothing is worn. 

Wound myiasis:

• Wound myiasis is caused by the larvae of Cochliomyia hominivorax (New World screwworm fly) and Chrysomya bezziana (Old World screwworm fly). Patients may report bleeding and pain within preexisting wounds. In this particular form, constitutional symptoms, such as fever and chills, and laboratory abnormality with leukocytosis and eosinophilia may be seen. If wound myiasis occurs on a periorificial location on the head, the larvae can burrow into the nasal bones, eyes, or brain tissue, with serious sequelae including sepsis, blindness, and death.
• Infestation occurs when ova (up to 200-300 at a time) are laid on a wound or body orifice (eg, nasal, ocular, genital, newborn umbilicus), and hatched larvae burrow into living tissue to feed and develop. Larvae mature after 7 days and drop to the ground. Individuals living in rural and endemic regions where livestock are raised are at increased risk, especially individuals with open wounds or sores (even very small) and those who are immunocompromised.

Migratory myiasis:

• Migratory, or creeping, myiasis is caused by Hypoderma bovis or Gasterophilus intestinalis larvae. Clinically, migratory myiasis presents as pruritic serpentine lesions similar to those of cutaneous larva migrans. This form is found in individuals working or living near cattle and horses.

Myalgias may represent myiasis due to a less common species of botfly (Hypoderma lineatum).

Larval infestation of the eye (ophthalmomyiasis) may be internal or external.