June 6 (UPI) -- A second case of New World fly larvae infection was confirmed in Texas this week in a month-old calf located about six miles from where the first case was discovered.
On Friday, the U.S. Department of Agriculture announced a second confirmed case of the disease, which was identified in Zavala County, Texas, but 5.6 miles from the first case.
The second case was confirmed just 24 hours after the first, which was detected in a three-week-old calf, prompting the USDA to increase surveillance and take other measures to prevent the spread of the infection.
The New World screwworm is spread by flies that lay eggs in exposed flesh of live animals—livestock, pets, wild animals, and humans are susceptible. When the eggs hatch, the fly larvae, or maggots, develop and penetrate the muscles.
Although screwworm was eradicated in the United States in the 1960s, serious infestations in Central America have gradually moved toward the southern border in recent years and were detected here in 2025, according to the U.S. Department of Agriculture.
«"Along with our partners in Texas, we are responding quickly and decisively," the USDA said in a statement about the second case, published on X.
«"We've defeated this pest before, and we'll do it again," the agency stated. "American livestock producers have the FULL support of the USDA.".
According to the agency, the primary method for controlling the spread of the parasitic fly is a combination of trapping flies for analysis, creating detection and quarantine zones in areas where infestation has been confirmed, and releasing sterile flies into detection areas to prevent the spread of infected insects.
The USDA urged residents in the area where the two cases were reported to check their pets and livestock for festering or enlarging wounds, as well as fly larvae or eggs around abdominal openings such as the nose, ears or genitals, or around the navel of newborn animals.
Although human infestation with blowfly larvae is relatively rare, infestation can occur in a similar manner to animals and require immediate medical attention.