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Cattle ranchers in Texas and around the country are concerned that the screwworm, a parasitic fly that was once eradicated in the U.S., is threatening a comeback from the Mexican border and recent talk from President Trump about importing beef from Argentina is no long-term solution for a beef supply chain already under stress or consumers who have watched beef prices hit record levels. The New World screwworm is a parasitic fly that lays eggs in the open wounds of warm-blooded animals. The larvae then hatches from the eggs and burrows into tissue of animals to feed on them. If caught early, the sick animal can be treated and survive. Human cases are rare but can be painful and require medical attention. In August, the the U.S. Department of Agriculture said in a statement the Department of Health and Human Services and Centers for Disease Control and Prevention identified a case of the flesh-eating parasite in a person in Maryland who returned to the U.S. after traveling to El Salvador. The New World screwworm was successfully eradicated from the United States in 1966. But the Maryland case and other recent appearances in Mexico have cattle ranchers in Texas and around the country on edge. Mexico's National Service of Agro-Alimentary Health, Safety, and Quality confirmed on October 6 another case of the flesh-eating screwworm parasite in Nuevo Leon, a city that borders the U.S. It marked the country's second confirmed case in approximately two weeks. "Texas is a material contributor to the beef industry," said Andrew Coppin, co-founder and CEO of ranch management company Ranchbot Monitoring Solutions. "You have millions of beef cattle along the southern border alone." The U.S. Department of Agriculture has closed the border to Mexico for imports of live cattle, bison, and horses, on and off, since 2024 due to the spread of the New World screwworm. The border is currently closed. Before the closure, Mexico was an exporter of calves to the U.S., with USDA data showing the U.S. imported over one million cattle annually, approximately 3.3% of the U.S. total calf crop. Sixth-generation Texas rancher James Clement III tells CNBC the key to eradicating the screwworm threat is years out. To combat the spread of the flies, the USDA disperses sterile flies into the area to stop the mating, a scientific method known as sterile insect technique (SIT). It was the reason for the successful eradication of the flies in the U.S. But Clement said the flies used previously were brought in from Panama and while the USDA has said it is committed to developing a domestic sterile fly production facility, "that is at least two or three years away. By then it will be too little to late," he said. The USDA did not respond to a request for comment. Clement, whose family business has operated multiple ranches over the last 400 years, said American ranching has evolved and has become more efficient. While this is good for production, in times of threats like biohazards such as screwworm, it is a challenge. "We require less labor now so it would be difficult and challenging to detect an infected cattle," he said. "We don't have the people to check every head of cattle daily. Most of this cattle are free range and the grass pastures are large." According to government data, as of July 2025, the U.S. cattle herd is approximately 94.2 million head, the lowest inventory since 1951. Coppin tells CNBC the key component to increasing herd size is water. "Typically, ranches have thousands of acres and cattle," Coppin said. "Less grasslands as a result of less water equals smaller herds." He estimated 30% of the U.S. is still in drought conditions. "The question ranchers are asking themselves is, will I have enough feed to feed my herd? This is why grasslands are important. Feed is a big input cost that eats into the margin of ranchers," he said. Coppin said while the importing of beef from Argentina may lower the cost of beef for consumers (futures had dropped sharply after Trump's comments but have since trended up again), for ranchers facing drought and screwworm, the incentives to increasing herd size are dwindling. "Ranchers don't want their product to be substituted," Coppin said. Recently, some U.S. ranchers have begun taking steps to start rebuilding herds. However, ranchers and beef supply chain experts like Coppin say it takes about two years before beef output rises because it takes time to raise full-grown cattle. The National Cattlemen's Beef Association said in statement on Monday after President Trump floated his idea to import beef from Argentina over the weekend that it was urging President Trump and Congress to allow the market to work rather intervene and harm rural America. "This plan only creates chaos at a critical time of the year for American cattle producers, while doing nothing to lower grocery store prices," said Colin Woodall, CEO of NCBA. The NCBA also cited Argentina's "deeply unbalanced trade relationship" with the U.S. In the past five years, Argentina has sold more than $801 million of beef into the U.S. market. By comparison, the U.S. has sold just over $7 million worth of American beef to Argentina, according to NCBA data. It noted Argentina also has a history of foot-and-mouth disease, which if brought to the United States, could decimate domestic livestock production. Clement said having the government step in and try to regulate the markets is not what the U.S. should be focused on. "The market will take care of itself," Clement said. "We need the government preventing and stamping out screwworm. Then we can recruit the next generation saying, 'ranching is a profession that you can do to take care of your family, and have a good quality of life. The government will look after us through biosecurity and the prevention of animal disease. Not manipulating the markets.'"
