Inside the Fight Against a Flesh-Eating Fly in Mexico

The New World screwworm is a flesh-eating fly that preys on livestock and other animals.Now imagine an entire plant producing millions of such insects a week.

The larvae feasts on a mixture of cellulose, egg, milk and cow’s blood that mimics flesh.The result is a pungent, sickly sweet odor of rotting tissue — one that invades your nostrils and lingers.“You get used to it,” said Dr.José Luis Quintero, who helps run such a laboratory in Mexico.

“It’s part of the job.”Mexican officials have been racing to combat the first major screwworm infestation in the country in decades, one that has already disrupted a strained cattle industry in both Mexico and the United States.Screwworms were largely eradicated in the region by the early 2000s, but a combination of factors has allowed the flies to make an unwelcome comeback, shutting the U.S.

border to Mexican cattle imports last year and contributing to high U.S.beef prices.In the town of Metapa, which sits along the Mexican border with Guatemala, a newly refurbished plant has become Mexico’s main solution to the parasite that has already resulted in more than 34,000 cumulative cases in all but two of Mexico’s 32 states since the first incidence was detected in November 2024.

The outbreak is estimated to cost billions of dollars combined in losses and the measures to fight it....