The New World screwworm fly has arrived in south Texas, and state officials have set a 12-mile quarantine zone to keep animals from moving out of the area without an inspection. The U.S. Department of Agriculture said Monday that two new cases brought the total reported cases to four.
One of the new cases was a dog in Lea County, New Mexico, just across the state line. The other was a calf in La Salle County, Texas, putting the pest inside the state that is home to $17 billion worth of cattle and central to the wider $113 billion U.S. cattle industry.
The arrival matters because the screwworm is not a new problem, only a returning one. It was an annual warm-weather scourge for cattle ranchers from at least the 1930s through the 1960s, and officials say they are now racing to eradicate a deadly flesh-eating parasite not seen in Texas since 1966. The U.S. once drove it out by breeding sterile male flies and dropping them from planes to mate with wild females, a campaign that worked for decades.
That history is now colliding with a fresh spread northward. The deadly flies were detected in Mexico late in 2024 after years of being contained at the southern end of Panama, raising the pressure on border states as the pest pushed into Texas and New Mexico. For livestock owners, the immediate consequence is movement control: animals in the quarantine area cannot leave without inspection, a sign that officials are trying to stop the infestation before it widens.
The unanswered question is whether containment will hold before the parasite spreads beyond the current cases. Texas has seen the screwworm before and beaten it back, but this time it is starting from a live foothold in the state’s cattle country, and the next few weeks will show whether the quarantine is enough to keep four cases from becoming many more.
