CHICAGO — New World screwworm, a parasitic fly that eats warm-blooded animals alive, was found in a calf in Texas, the U.S. Department of Agriculture said Wednesday evening, exposing the nation's cattle herd to a serious new threat.
Earlier, U.S. Secretary of Agriculture Brooke Rollins said additional agency personnel arrived in south Texas to provide support on the ground amid a suspected case of the flesh-eating screwworm parasite in the area.
"This potential New World Screworm detection is being fully contained and is not a harm to the American food supply or consumer safety," she said in a post on social media.
A sample of screwworms collected in the morning are displayed July 4 at a veterinary clinic in Tapachula, Chiapas state, Mexico.
U.S. cattle ranchers have been preparing for the screwworm for more than a year.
The fly can infest people and pets, but the risk to humans is low, experts said. The fly poses no food safety issues.
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"We have already activated personnel on the ground and are working with local partners," USDA said on social media.
Widespread market chatter about the suspected case hung over cattle futures, which traders said were long sensitive to threats of New World screwworm.
The parasite moved north through Mexico for more than a year. Market players believe an infestation in the U.S. could reduce demand for beef from consumers nervous about the flesh-eating pest, but would be bullish in the long term by reducing the U.S. cattle supply.
Screwworms are parasitic flies whose females lay eggs in wounds of any warm-blooded animal. Once the eggs hatch, hundreds of screwworm larvae use their sharp mouths to burrow through living flesh, eventually killing their host if left untreated.
An outbreak of screwworm in the U.S. could cause $1.8 billion in damage to Texas' economy alone and would likely raise U.S. beef prices by shrinking the U.S. cattle supply, experts said.
The U.S. kept its border with Mexico closed to cattle imports for more than a year to prevent the destructive parasite from reaching U.S. border states. The U.S. also spent millions of dollars to slow its advance through Mexico, investing in sterile fly production facilities, expanding trapping efforts and increasing livestock surveillance.
