Wound myiasis in urban and suburban United States

Background: The epidemiologic characteristics of human myiasis in the United States remain undefined. Objective: To describe the most common clinical conditions associated with human myiasis and the causative maggot species. Methods: Multicenter, prospective observational study of urban and suburban patients who were infested with maggots. Results: Forty-two cases of US-acquired myiasis were collected from 20 participating centers. Most infestations occurred within preexisting wounds. No cases of tissue invasion were recorded. Host age averaged 60 years, with a male-female ratio of 5.5:1. Homelessness, alcoholism, and peripheral vascular disease were frequent cofactors. Two patients (5%) were hospitalized at the time of their infestation. The most common species was Phaenicia sericata (green blowfly; family: Calliphoridae). Other blowflies, flesh flies (Sarcophagidae), and humpbacked flies (Phoridae) also were identified. In 6 eases, 2 coinfesting species were identified. Conclusions: Results of this prospective study of myiasis differ significantly from those of our analysis of previously published reports and suggest that most cases of human myiasis are caused by noninvasive blowflies laying eggs in preexisting wounds. Five percent of infestations were nosocomially acquired and not necessarily associated with patient neglect.