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

Mexico activated emergency controls Monday after detecting a new case of New World screwworm in cattle in the northern border state of Nuevo Leon, the closest case to the U.S. border since the outbreak began last year. —Peter Burke, FOXNews.com, 24 Sep. 2025

Fears about the screwworm parasite have led the USDA to block livestock from crossing from Mexico to the U.S. to safeguard the nation's food supply. —Alina Selyukh, NPR, 18 Sep. 2025

But screwworms aren't the only dangerous pathogens sickening Americans this summer. —N'dea Yancey-Bragg, USA Today, 28 Aug. 2025

The parasite — the larva of the New World screwworm fly — can devastate cattle herds and is rife in parts of Central America and Mexico. —Patrick Smith, NBC news, 25 Aug. 2025

Kennedy did declare, however, that the FDA can fast-track approval processes for antiparasitic drugs to be used in animals with screwworm infestations. —Madhusree Mukerjee, Scientific American, 25 Aug. 2025

New World screwworms are the parasitic larva of a metallic blue blow fly species called Cochliomyia hominivorax. —Jamie Gumbrecht, CNN Money, 25 Aug. 2025

The Food and Drug Administration (FDA) became authorized Tuesday to allow the use of animal drugs to treat or prevent infestations caused by the New World screwworm, a flesh-eating parasite that has recently disrupted the cattle industry. —Alejandra O’Connell-Domenech, The Hill, 19 Aug. 2025

The screwworm name refers to the pest’s feeding behavior, since the maggots burrow or screw into an animal’s wound. —Brayden Garcia, Fort Worth Star-Telegram, 23 July 2025

Word History

First Known Use

1846, in the meaning defined at sense 1

Kids 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

b

: secondary screwworm

2

: a dipteran fly of the genus Chrysomya (C. bezziana) that causes myiasis in Africa and southern Asia