Flesh-eating screwworm found in Texas calf

What happened

New World screwworm, a deadly flesh-eating parasite, has been confirmed in a calf in south Texas, the U.S. Department of Agriculture said late Wednesday. It was the first case of the fly-borne parasite found in U.S. livestock since 1966.

Who said what

Screwworms are “parasitic flies whose females lay eggs in open wounds” on “any warm-blooded animal,” hatching hundreds of larvae that “use their sharp mouths to burrow through living flesh, eventually killing their host if left untreated,” Reuters said. Human cases are “rare,” and the fly “poses no food safety issues.”

The U.S. has been preparing for the parasite’s arrival, sealing the U.S. southern border to livestock since screwworms were found spreading north through Mexico in 2024. If “more screwworms are found” in the U.S. beyond this one case, it “could devastate the American cattle industry,” The New York Times said. The nation’s cattle herd is “already at its smallest since the 1950s,” The Wall Street Journal said.

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The USDA is “taking immediate action” to “contain” and “eradicate this case,” said Agriculture Secretary Brooke Rollins, including forming a 12.4-mile “infested zone” quarantine around the calf, increasing monitoring and releasing millions of sterile New World screwworm flies to shrink the population.

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