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
The New World screwworm Bessent referenced — a parasitic fly that eats cattle and other warm-blooded animals alive — has been spreading in Central America and Mexico, and prompted Washington to suspend cattle imports from Mexico in May.
—
Alia Shoaib, MSNBC Newsweek, 17 Nov. 2025
A number of factors have kept prices stubbornly high, including widespread drought and the reemergence of a flesh-eating screwworm in Mexican cattle.
—Mackensy Lunsford, Nashville Tennessean, 23 Oct. 2025
The screwworms can cause extensive tissue damage and bacterial superinfection, the CDC says.
—Dominique Mosbergen, Time, 26 Aug. 2025
When was New World screwworm last reported in US, Central America?
—Jenna Prestininzi, Freep.com, 26 Aug. 2025
Reuters reported last week that the CDC had confirmed a case of New World screwworm in Maryland from a person who traveled from Guatemala.
—Ashley J. Dimella, FOXNews.com, 25 Aug. 2025
Through this technique, the U.S. managed to eradicate New World screwworm in 1966.
—Rachel Treisman, NPR, 25 Aug. 2025
The technique worked in the 1960s when the United States suffered its last screwworm outbreak.
—Patrick Smith, NBC news, 25 Aug. 2025
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Alia Shoaib, MSNBC Newsweek, 17 Nov. 2025
A number of factors have kept prices stubbornly high, including widespread drought and the reemergence of a flesh-eating screwworm in Mexican cattle.
—Mackensy Lunsford, Nashville Tennessean, 23 Oct. 2025
The screwworms can cause extensive tissue damage and bacterial superinfection, the CDC says.
—Dominique Mosbergen, Time, 26 Aug. 2025
When was New World screwworm last reported in US, Central America?
—Jenna Prestininzi, Freep.com, 26 Aug. 2025
Reuters reported last week that the CDC had confirmed a case of New World screwworm in Maryland from a person who traveled from Guatemala.
—Ashley J. Dimella, FOXNews.com, 25 Aug. 2025
Through this technique, the U.S. managed to eradicate New World screwworm in 1966.
—Rachel Treisman, NPR, 25 Aug. 2025
The technique worked in the 1960s when the United States suffered its last screwworm outbreak.
—Patrick Smith, NBC news, 25 Aug. 2025
Cite this Entry
“Screwworm.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/screwworm. Accessed 5 Jan. 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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