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USDA reports three new cases of screwworm, bringing total to 15

By Thomson Reuters Jun 21, 2026 | 6:55 PM

June 21 (Reuters) – The number of U.S. cases of New World screwworm has risen to 15 after three more animals tested positive ​in Texas, the Department of Agriculture said ‌in a post on social media on Sunday.

The USDA announcement comes nearly three weeks after the first domestic screwworm infestation in six decades was found in a Texas calf.

New World ‌screwworm ​is a parasitic fly that ⁠eats warm-blooded animals alive ⁠and can infect livestock, pets, wildlife and, in rare cases, people. The larvae burrow into the living tissue of animals and cause severe wounds that ​can eventually kill, leading to signficant economic losses for ranchers.

The USDA said it will continue aggressive ⁠eradication efforts in affected ⁠areas, including the dispersal of tens of ​millions of sterile flies that halt screwworm reproduction.

One lamb ​in Crockett County and two calves in Edwards ‌County, Texas tested positive for screwworm in the past 24 hours, according to the USDA’s Sunday evening post on X.

Texas ranchers have been bracing for screwworm to ⁠cross into the U.S. for the past year, as the pest advanced north in Mexico. Experts have predicted that ⁠a widespread ‌outbreak could cost the state $1.8 billion ⁠in economic damage and devastate wildlife.

The ​USDA broke ‌ground in April on a facility ​to produce ⁠sterile flies, which experts describe as the best tool for combating the pest, but it will not come online until late 2027.

(Reporting by Costas Pitas and Jack Queen; Editing by Sergio Non, Christian Schmollinger ​and Lincoln Feast.)