A flesh-eating parasite that feeds on warm-blooded animals has been detected in the US for the first time since 1966.

New World Screwworm (NWS) has been advancing across Mexico for the past year and has now been found in a calf in Texas, the US Department of Agriculture (USDA) said on Wednesday evening. Efforts to delay the arrival of screwworm in the US have been under way since cases began increasing in Central America and Mexico.

The case was confirmed in the town of La Pryor, Texas, approximately 30 miles (48km) from the southern US-Mexico border. Cattle ranchers in the US have been fearing an outbreak could shrink herds, reduce beef production and drive prices higher for consumers.

Screwworms are parasitic flies whose females lay eggs in open wounds and mucous membranes on animals. When the eggs hatch, hundreds of larvae burrow through living flesh with sharp mouths, eventually killing their host if left untreated. NWS can infest people and pets as well, but the risk to humans is low, and human cases of screwworm are rare. The fly poses no food safety issues.

This first case in 60 years was detected in a three-week-old calf, with the larvae found in its umbilical area. The movement of infested animals is the most common way they spread, so the USDA and Texas authorities are establishing a 20km (12.4 miles) detection and quarantine zone. Plans are also in motion to release millions of sterile screwworm flies, as the females only mate once in their lifetime, and any eggs they lay will be unfertilised and will not hatch.

The USDA has been preparing for a possible outbreak for some time, and they say efforts have delayed the parasite’s arrival by a year. Agriculture Secretary Brooke Rollins assured ranchers that USDA personnel have already arrived in South Texas to support operations. She called on livestock producers to be vigilant.

However, Texas Agriculture Commissioner Sid Miller has been critical of the federal response. “Instead of using every available tool, USDA moved too slowly and relied solely on a partial solution that takes years to fully implement,” he told Reuters, referring to the release of sterile flies.