screwworm
noun
screw·worm
ˈskrü-ˌwərm 
1
: a blowfly (Cochliomyia 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 larva
2
: any of several flies other than the screwworm and especially their larvae which parasitize the flesh of mammals
Examples of screwworm in a Sentence
Recent Examples on the Web
In the meantime, the agency is investing $21 million to transform a fruit fly breeding center in far southern Mexico into a screwworm fly production site, with operations set to begin this summer.
—
Marley Malenfant, Austin American Statesman, 12 Feb. 2026
The Mexican cattle industry has been hit hard by New World screwworm fly larvae infestations, and the U.S. has closed the border since July to imports of cattle, bison and horses.
—John Hanna, Fortune, 10 Feb. 2026
The best way to kill screwworms hasn’t significantly changed since the 1960s.
—Bloomberg Wire, Dallas Morning News, 7 Feb. 2026
The strategy helped eradicate the New World screwworm from the Florida Keys in 2017.
—Alix Martichoux, The Hill, 21 Jan. 2026
The New World screwworm is a parasitic fly that lays eggs in the open wounds of warm-blooded animals.
—Lori Ann Larocco, CNBC, 21 Oct. 2025
Also look for screwworm larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia, or the navel of newborn animals.
—Beth Mole, ArsTechnica, 24 Sep. 2025
There is no approved human treatment for screwworm infestations.
—Dominique Mosbergen, Time, 26 Aug. 2025
Mexico is training rescue dogs to detect flesh-eating screwworm larvae in livestock wounds.
—Moná Thomas, People.com, 11 Aug. 2025
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Marley Malenfant, Austin American Statesman, 12 Feb. 2026
The Mexican cattle industry has been hit hard by New World screwworm fly larvae infestations, and the U.S. has closed the border since July to imports of cattle, bison and horses.
—John Hanna, Fortune, 10 Feb. 2026
The best way to kill screwworms hasn’t significantly changed since the 1960s.
—Bloomberg Wire, Dallas Morning News, 7 Feb. 2026
The strategy helped eradicate the New World screwworm from the Florida Keys in 2017.
—Alix Martichoux, The Hill, 21 Jan. 2026
The New World screwworm is a parasitic fly that lays eggs in the open wounds of warm-blooded animals.
—Lori Ann Larocco, CNBC, 21 Oct. 2025
Also look for screwworm larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia, or the navel of newborn animals.
—Beth Mole, ArsTechnica, 24 Sep. 2025
There is no approved human treatment for screwworm infestations.
—Dominique Mosbergen, Time, 26 Aug. 2025
Mexico is training rescue dogs to detect flesh-eating screwworm larvae in livestock wounds.
—Moná Thomas, People.com, 11 Aug. 2025
Cite this Entry
“Screwworm.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/screwworm. Accessed 20 Feb. 2026.
Copy CitationKids Definition
screwworm
noun
screw·worm
ˈskrü-ˌwərm
: the larva of a blowfly of the warm parts of America that develops in the wounds or sores of mammals and may cause disease or death
also
: the blowfly itself
Medical Definition
screwworm
noun
screw·worm
ˈskrü-ˌwərm
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 larva
2
: a dipteran fly of the genus Chrysomya (C. bezziana) that causes myiasis in Africa and southern Asia
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