Agriculture Department officials have confirmed a case of New World screwworm in a South Texas calf, marking the first detection of the pest in U.S. livestock in decades. 

Agriculture Secretary Brooke Rollins said in a press call Wednesday evening that the pest has been found in a 3-week-old calf in La Pryor. At this point, it is the only U.S. case of the flesh-eating pest USDA "is tracking right now, and the only one that has been confirmed," she said.

USDA's Animal and Plant Health Inspection Service has established a 20-kilometer infested zone around the detection site, where it is implementing quarantines, movement controls and surveillance for the pest, Rollins said. She added that the agency is immediately deploying 4 million sterile flies in ground release chambers in the area on top of the 4 million sterile flies it already drops aerially over the region each week.

"If we all work together and follow the animal treatment protocols and movement restriction guidance, there is no reason to believe that this incursion will result in an establishment of the pest in our country," she said. 

USDA Undersecretary for Marketing and Regulatory Programs Dudley Hoskins said agency officials "will continue to try to flood the zone with as many sterile flies as we can get there until we have confidence that we've knocked it down in that area and we can return to our normal posture."

Larvae of the New World screwworm, a parasitic fly, burrow into the flesh of livestock using sharp mouth hooks. The pest was widely considered to be eradicated from the U.S. by 1966, though it re-emerged in the Southwestern U.S. for a few years in the late 1970s, according to a report from the United Nations Food and Agriculture Organization. After that, it was driven off U.S. soil until 2016, when an outbreak in the Florida Keys infested local deer before officials stamped it out.

However, it never disappeared from Latin America, and in recent years, has been pushing steadily northward through Central America and Mexico. Earlier this week, USDA confirmed a case just 25 miles from the U.S.-Mexico border in the Mexican state of Coahuila. 

Rollins said around 400 to 500 million sterile flies per week are needed to push the fly past the Darién Gap, a stretch of land along the border of Panama and Colombia. About 100 million flies are produced at a facility in Panama, and another 100 million flies will be produced at a facility in Mexico now under construction, which Rollins said could open as soon as next month.

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A $750 million facility being built in Edinburg, Texas, which will be capable of producing 300 million sterile flies per week, won't start operating until next fall, Rollins said. 

USDA last year suspended live cattle, horse and bison imports from Mexico over concerns about the fly's northward spread. She stressed Wednesday that the pest spreads to new areas through the movement of animals, "not because the fly flies tens of miles or hundreds of miles on its own."

Texas State Veterinarian Bud Dinges urged producers to immediately report suspected infestations and check their animals as often as possible for wounds. He said New World screwworm cases are "highly treatable," and emphasized that the pest does not pose a threat to food safety. 

American Livestock Markets and Dealers Association CEO Tim Niedecken told Agri-Pulse ranchers should inspect their animals closely for wounds that don't seem to heal, especially following branding, castration, and ear tagging, and consult their veterinarians if they notice anything that seems off.

"The livestock industry's been preparing for this possibility for well over a year and while it's going to create challenges, we'll work together to protect animal health and maintain all of our commerce," he said. 

Riley Rhodes, a cattle producer and co-owner of Live Oak Livestock Auction in Three Rivers, Texas, called the case "worrisome" for U.S. ranchers. However, "it's important that people don't panic," he stressed, noting that new technologies for fighting the pest have come online since U.S. producers last had to deal with it. 

"We've dealt with these things before," Rhodes told Agri-Pulse. "It's going to take a little time to eradicate it again, but it will happen. We'll get it done."

For more news, go to Agri-Pulse.com.