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MYIASIS

    Myiasis is the invasion of living vertebrate (including human) tissue by fly larvae. Various species of flies that normally deposit eggs or larvae on garbage, carrion, or corpses occasionally may deposit these stages on wounds or skin adjacent to draining infections. Other fly species are specifically adapted to deposit eggs that will hatch into larvae that invade intact skin or skin damaged by injury or disease. Flies in the former group are various house flies, blow flies (greenbottles and bluebottles), and flesh flies. The true myiasis-producers in the second group are bot flies and warble flies. Although bot fly and warble fly larvae usually infest nonhuman hosts, such as sheep, cattle, horses, rodents, deer, and other wild mammals, these larvae occasionally invade human tissues. Myiasis is most often cutaneous, but fly larvae may also invade the nose and throat, eye, ear, and intestinal or genitourinary tract.

    Dermal myiasis, arising in intact skin and caused by the human bot fly(Dermatobia hominis) in Central and South America and the tumbu fly (Cordylobia anthropophaga) in Africa appears as a painful or itching swelling with an opening at the skin surface. Observation of the opening under low magnification will reveal the posterior end of a moving larva, on which will be two dark circular areas, the respiratory openings (spiracular plates). If the larva is left in the skin, it will continue to feed just below the skin surface for several days to weeks and eventually back out and drop to the ground to complete its development.

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