New World Screwworm Cases in Texas Highlight Spread Challenge

In Kerrville, Texas, the authorities have identified two more cases of New World screwworm, underlining the difficulty of controlling a pest that could severely impact the livestock industry. The U.S. Department of Agriculture announced these findings on Monday.

The screwworm is a type of fly, producing larvae that consume live flesh instead of decomposed matter. Female flies lay their eggs in open wounds of any warm-blooded animal, including livestock. Wildlife, pets, and occasionally humans can also become infested.

The recent cases involved a calf and a dog located hundreds of miles apart in La Salle and Andrews counties. This brings the total number of confirmed cases to four. The screwworm was initially discovered last week in a 3-week-old calf, with another case found just a few miles away in a young calf.

“While we address these cases that require immediate attention and continue to sample suspected cases, we are simultaneously working to completely eradicate the pest,” stated Dudley Hoskins, Deputy Secretary of Marketing and Regulation.

In the U.S., the screwworm was eradicated in the 1960s but was an annual warm-weather scourge for cattle producers. The Department of Agriculture and the U.S. livestock industry have been striving to prevent an outbreak since the pest surfaced in Mexico at the end of 2024, after being confined to Panama’s southern edge for decades.

The government employs a method of breeding sterile male flies that mate with wild female flies, which only mate once in their lifetime. This results in no offspring being produced, gradually reducing outbreaks. Plans are underway to boost sterile fly production in facilities outside the U.S., while constructing a new plant in Texas.

Agriculture Secretary Brooke Rollins will receive updates about the infestation at the Insect Research Laboratory for Livestock in Kerrville, Texas, later on Monday.