Flesh-eating parasite arrives in US for first time in 60 years

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The New World Screwworm (NWS) has been advancing north through Mexico over the past year and has now arrived in La Pryor, Texas, about 30 miles (48 km) northeast of the US-Mexico border.

Cattle ranchers have been bracing for an outbreak, fearing it could shrink herds, reduce beef production and push up prices for customers.

Screwworms are parasitic flies whose females lay eggs in open wounds and membranes of warm-blooded animals.

Once the eggs have hatched, hundreds of larvae use their mouths to burrow through live flesh, killing the host if left untreated.

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NWS can infect people and pets as well, but the threat to humans is low and such cases are rare.

The most common way it spreads is through movement of infested animals.

The case, the first outbreak in 60 years, was found in a three-week old calf. It remains the only confirmed infestation in the country.

The USDA said it had established a 20-km control area around the detection site, and related sterile screwworm flies into the area. These flies mate with wild female screwworms to produce infertile eggs.

The USDA said it had been bracing for the arrival of the parasite for a while, and had managed to delay its spread by a year by closing the border with Mexico to livestock imports and investing in sterile fly production facilities.

However Texas Agriculture Commissioner Sid Miller was critical of the USDA for allowing screwworm to reach the US.

"Instead of using every available tool, USDA moved too slowly and relied ⁠solely on a partial solution that takes years to fully implement," he said.

Rollins said that the release of sterile flies was the most effective prevention tool and that USDA had heavily invested in production.