Medical Definition of screwworm
1: either of two dipteran flies of the genus Cochliomyia:a: one (C. hominivorax) of the warmer parts of America whose larva develops in sores or wounds or in the nostrils of mammals including humans with serious or sometimes fatal results; especially : its larvab: secondary screwworm
2: a dipteran fly of the genus Chrysomyia (C. bezziana) that causes myiasis in the Old World
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