TEXAS — Fifteen cases of New World screwworm have been confirmed in Texas and New Mexico as of June 21. The United States eradicated the parasite in 1982.

The confirmed cases have occurred in cows, goats, sheep, and a dog. The first detected case of the New World screwworm, scientifically known as Cochliomyia hominivorax, occurred on June 3 in a three-week-old calf in Zavala County, Texas, according to the United States Department of Agriculture. Female screwworms lay their eggs in open wounds of mammals. The larvae then burrow into and feed on the living flesh of the host, which can lead to secondary infections and death if untreated.

There are no reported human cases of locally acquired screwworm in the United States. A screwworm infection was reported in a person in 2025 who had returned to the United States after visiting El Salvador. Edwin Burgess, a veterinary entomologist at the University of Florida in Gainesville, noted the low risk of human cases. "You can look online and find horror stories about the number of human cases, but you have to think about the total population over that time period, and that number is itty-bitty in terms of a risk," Burgess said.

Screwworms do not infest food products such as meat, fruits, or vegetables. Phillip Kaufman, a veterinary entomologist at Texas A&M University in College Station, addressed concerns about food safety. "You are not going to have screwworms in your meat," Kaufman said.

During the 1950s and 1960s, federal agencies used the sterile insect technique to combat screwworm outbreaks in Texas and the southeastern United States. This technique involves breeding male screwworms and sterilizing them with radiation. These sterile males are then deployed into infested regions using trucks and aircraft. When sterile males mate with female screwworms, the females produce unviable eggs, which causes a population decline.

A 2024 USDA economic report estimated that a screwworm outbreak similar to the 1976 incident could exceed $1.8 billion annually in Texas alone. The Panama–United States Commission for the Eradication and Prevention of Screwworm Infestation in Livestock (COPEG) operates a facility in Panama that produces sterile flies. COPEG increased its production of sterile flies from 20 million to 40 million per week to approximately 115 million flies per week after screwworms were detected past the Guatemala–Mexico border in 2024. The last eradication effort in the United States required 500 million sterile flies to be exported each week. The USDA is employing epidemiological tracking and meteorological data to predict screwworm movement and identify areas for the release of sterile males.