The U.S. Department of Agriculture (USDA) announced it has begun dropping 100 million sterile flies each week along the U.S. border, including 50 miles inside Texas, to prevent New World Screwworm (NWS) from devastating American livestock. When NWS flesh-eating larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, sometimes even birds and in rare cases, people.
Scientists’ use of sterile files is the very same approach that successfully eradicated NWS from the U.S. during the previous invasion in the 1960s, containing it to South America. According to the USDA, the sterile fly strategy is so effective because female NWS flies only mate once in their lives, so if they mate with a sterile male, they lay unfertilized eggs that don’t hatch. But NWS began spreading northward and was detected again in southern Mexico by 2024.
In the lead up to Gov. Greg Abbott’s statewide disaster declaration on January 29, 2026, the Texas Standard’s Michael Marks reported that state officials had planned ahead for the potential threat to the ag industry. “I know that producers are really concerned about this. I’ve spoken with people who dealt with the screwworm back when it was a problem during the ‘60s, and they’re scared to go back to ranching under those conditions. It does seem like the state and federal agencies involved seem to be taking the threat seriously.”
The USDA says it has deployed more than 100 NWS traps and lures along the southern border in Texas, Arizona, New Mexico and California. More than 6,600 wild animals across 28 specials have also been examined in high-risk Texas counties, with no evidence of NWS found.
The map (above) shows the Mexico case status for New World Screwworm (NWS) through January 27, 2026, with the map created at 5:00 p.m. ET on Thursday, January 29. The map lists the 14,601 total animal cases detected within 400 miles of the U.S. border, 870 active animal cases.
While there has been no NWS cases detected along the border, or on the U.S. side of the border, the USDA confirms that a horse at an equine import quarantine facility in Florida tested positive for NWS on Friday. Authorities say the horse has been treated with medication and remains in quarantine.
