In Kerrville, Texas, U.S. officials confirmed two more cases of the New World screwworm. This highlights the challenge of controlling a pest that could severely impact the livestock industry, according to the Department of Agriculture on Monday.

The screwworm, actually a fly, lays its eggs in open wounds of warm-blooded animals. The larvae then consume live tissue. While this affects cattle primarily, wildlife, pets, and even humans can become infested.

The newest cases involved a calf and a dog, discovered in La Salle and Andrews counties, separated by hundreds of miles, stated the department. This brings the total number of confirmed cases to four. The screwworm first appeared last week in a three-week-old calf, and a second case was nearby in another young calf.

“While we address these urgent cases and continue sampling suspected cases, we’re simultaneously working to eradicate the pest entirely,” emphasized Dudley Hoskins, the department’s Deputy Secretary of Marketing and Regulation.

Before its eradication in the U.S. in the 1960s, the fly presented a significant problem to ranchers in warm climates annually. Since its detection in Mexico in late 2024, the U.S. Department of Agriculture and livestock industry have rushed to prevent an infestation, after being geographically confined to southern Panama for decades.

The government uses sterile male flies to combat the screwworm. These males mate with wild females, which mate only once. With no offspring produced from these interactions, the outbreaks gradually decrease.

The department plans to increase the production of sterile flies in facilities outside the U.S. while building a fly production plant in Texas.

Agriculture Secretary Brooke Rollins is set to receive updates on the infestation Monday afternoon at the Livestock Insect Research Laboratory in Kerrville, Texas.