Flesh-eating screwworms are feasting on human flesh in Mexico

“Since the flesh-eating screwworm fly reinvaded Mexico in 2024, human cases of the voracious parasite have been mounting….there have been over 500 human cases in 2025 and 2026.” A study of 200 confirmed cases “found that the infestation pace is increasing,” reports Ars Technica:

Among the 200 confirmed cases in the study, six deaths were reported. At least one of the deaths was directly caused by the fly’s maggots…

The New World screwworm (NWS) fly was once endemic in Mexico—as well as the US. The flies lay hundreds of eggs in the wounds, inflamed tissue, mucous membranes, and orifices of warm-blooded creatures. The resulting maggots hatch within a day and begin ravenously feasting on the living flesh of their victims. While the fly’s maggots generate ghastly, life-threatening wounds in a variety of warm-blooded species, including humans, they’re particularly devastating to livestock.

Amid a decades-long eradication effort, the fly’s populations were wiped out from the US, Mexico, and Central America. This was largely done with massive aerial releases of sterilized male flies, a technique that works because female NWS flies only mate once in their lifespans. Mexico declared NWS eradicated in 2003. Panama declared eradication in 2006 and kept an active biological barrier along the Darién Gap at the border with Colombia. But in 2022, the barrier was breached, and Mexico began seeing cases in animals in 2024.

Meanwhile, the “US and Mexico took a major step in the battle against New World screwworm” a month ago,  “opening a facility in Metapa, near Mexico’s southern border, to produce sterile flies that authorities believe is the best method for stopping the flesh-eating parasite.”

The production facility will send the pupae in cold containers by plane to be distributed in both Mexico and the United States. A researcher said the flies will be spread “in the most strategic manner possible, to impact this as quickly as possible and push it back south, out of the United States, out of Mexico,” with the goal of eradicating screwworm completely.

“It’s very opportune that the Metapa plant is opening,” said Texas A&M University’s Phillip Kaufman. But it will “take them a few months to get up to full production.”

The facility will first sterilize screwworm pupae with radiation, and then release the sterilized flies to mate with wild flies. Since females usually mate only once in their life, mating with the sterile males prevents them from giving birth to screwworms.

Not all news about parasites is bad. A new vaccine fights hookworm, which makes millions of people around the world lethargic.

The African nation of Guinea recently eradicated sleeping sickness, a parasitic disease carried by the tsetse fly that causes irreversible brain damage, aggressiveness, psychosis, and then death, if left untreated.

Niger recently became the first nation in Africa to eliminate river blindness, a disease spread by flies that breed near rivers. Those flies carry long thin parasitic worms that burrow in a victim’s skin.

Parasites can take years for countries to eradicate. It took nearly 40 years for the world to largely eradicate Guinea worms, nasty parasites that caused tens of millions of people to scream with unbearable pain. But by 2023, Guinea worms had been eradicated in at least 17 countries, and “no guinea worm was reported” in 2024.

Guinea worms used to inflict burning pain on millions of people in Africa and South Asia every year. They would grow up to 3 feet long while living inside a person’s body, then burst out of their foot or other sensitive areas of their anatomy, such as their eyeball or their penis.

“With a guinea worm infection, you get a gross open wound from which the worm emerges over a period of weeks to months with extreme painfulness. There were millions of cases in the 80s, and now there are none. Incredible human progress.”

“It’s possible that the worm is evolutionarily adapted to cause prolonged pain and suffering. Since this will increase the chance that the host will put their foot in the water to soothe the pain, and that can help the worm get to the next stage in its life cycle,” notes a scientist.

Scientists have discovered drugs that can kill malaria parasites inside mosquitoes.