Second New World Screwworm case confirmed in Texas cattle

June 6 (UPI) -- A second case of New World screwworm was confirmed in Texas this week in a one-month old calf nearly six miles from where the first case was detected.

The U.S. Department of Agriculture announced the second confirmed case on Friday, which was detected in Zavala County, Texas, but 5.6 miles away from the first one.

The second case was confirmed just 24 hours after the first, which had been detected in a three-week old calf, and has spurred the USDA to step up surveillance, as well as take other actions to prevent the infestation from spreading.

New World screwworm is spread by flies that lay their eggs in the exposed flesh of living animals -- livestock, pets, wildlife and humans are all susceptible -- and when the fly larvae, or maggots, emerge from the eggs they burrow through muscle as they grow.

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Although screwworm was eradicated from the United States in the 1960s, severe infestations in recent years in Central America slowly moved toward the southern border and was detected here in 2025, according to the USDA.

"With our partners in Texas, we are responding with speed and strength," the USDA said in a statement about the second case that was posted on X.

"We have defeated this pest before, and we will do it again," the agency said. "America's livestock producers have USDA's FULL support."

The primary way of controlling the spread of New World screwworm is a combination of trapping flies for testing, implementing detection and quarantine zones where it confirmed, and releasing sterile flies into the area it has been detected to prevent infected insects from reproducing, the agency said.

The USDA has encouraged people in the area of the two cases to check their pets and livestock for draining or enlarging wounds, if not maggots or eggs around bodily opening such as the nose, ears or genitals, or around the navel of newborn animals.

Although screwworm infection in humans is relatively rare, the infestations can happen in ways similar to animals and require immediate medical attention.

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