Campeche, MEX — Health authorities in Mexico have confirmed the country’s first known human fatality caused by the screwworm parasite, a flesh-eating fly larva that primarily infests livestock. An 86-year-old man in the southern state of Campeche died in late June after developing a severe tissue infection (myiasis) caused by Cochliomyia hominivorax, commonly called the New World screwworm. Officials noted that while the patient’s official cause of death was complications from skin cancer, the screwworm infestation contributed significantly and has been recorded in epidemiological surveillance as a screwworm-related death – the first of its kind in Mexico.
The case has alarmed health experts, as screwworm had been largely eradicated from Mexico’s livestock since the 1990s via a massive eradication program, and human cases are extremely rare globally. The victim, whose name was not disclosed, was a resident of rural Candelaria municipality in Campeche. According to a report from the Federal Ministry of Health, he already had an advanced malignant skin lesion on his scalp and likely attracted screwworm flies to those open wounds. The fly’s larvae then infested the wound, exacerbating his condition.
Screwworm larvae are notorious for literally eating living flesh. The female screwworm fly lays eggs on open wounds or mucous membranes of animals (and occasionally humans). When the maggots hatch, they burrow into the tissue, feeding on the host’s live flesh – hence the Latin name hominivorax, meaning “man-eater.” If untreated, a screwworm infestation can cause severe tissue destruction, secondary infections, and potentially death of the host.
The man’s family brought him to a hospital only when his wound became severely maggot-infested, officials said. Despite medical efforts, including wound debridement and antiparasitic treatment, his condition was complicated by his underlying cancer and the infection, and he passed away. Laboratory analysis confirmed the larvae were Cochliomyia hominivorax, the screwworm species.
The Ministry of Health added this incident to its weekly epidemiological bulletin, marking it as the first human case of screwworm myiasis resulting in death on record in Mexico. Typically, screwworm cases in humans are very rare – only a handful have been reported in the Americas over the past several decades, often involving travelers or people in very remote areas.
“This case, while isolated, is a stark reminder that eradicated pests can re-emerge under certain conditions,” said Dr. Jesús Bolio, a parasitologist at UNAM. He explained that Mexico’s celebrated screwworm eradication campaign, which began in the 1970s, used the sterile insect technique to wipe out the screwworm fly population. By 1991, Mexico was declared free of screwworm, and the frontier of infestation was pushed to Panama. However, sporadic cases in deer or other wildlife have occasionally been detected in southern Mexico, suggesting the flies sometimes creep back across borders.
In this instance, Campeche officials suspect the man’s remote ranch may have had an infested animal that attracted flies, or that wild flies from Central America found his unattended wound. The government is now stepping up surveillance in Campeche’s border region to see if any livestock or other people have screwworm infestations. So far, none have been reported, indicating this might be an isolated case.
The Health Ministry is urging the public – especially those in rural and ranching communities – to maintain good wound care and hygiene for both people and animals. “Any wound should be cleaned and covered to prevent attracting flies,” said Dr. Gloria López, director of zoonosis at the Ministry. She also advised ranchers to regularly inspect their cattle, pigs, and other animals for signs of myiasis (maggot-infested wounds) and to report any suspected screwworm cases to veterinary authorities immediately.
What is the screwworm exactly? The screwworm fly looks like a metallic green blowfly. It lays clusters of eggs on wounds. The hatched larvae then screw themselves into the flesh (hence the name), sometimes reaching deep into muscle or nasal sinuses. In livestock, untreated screwworm infestation can be fatal. Mexico’s eradication success story involved releasing millions of sterile male flies to break the breeding cycle – a pioneering use of biotechnology in pest control.
Given Mexico’s long screwworm-free status, many younger vets and doctors have never seen a case, which might hinder quick diagnosis. To address that, the Health Ministry has circulated an alert to medical personnel with photos and guidelines on recognizing myiasis and specifically identifying C. hominivorax larvae. They note the larvae have distinctive pigmented tracheal tubes and oral hooks that differentiate them from common fly maggots that typically only eat dead tissue.
In the unfortunate Campeche case, some have asked if earlier detection could have saved the man. Possibly, yes. If the screwworm infestation had been caught early, aggressive treatment might have controlled it. However, his advanced cancer made it complicated. The Ministry’s bulletin noted that even though clinically his death was attributed to skin cancer, they included it in screwworm surveillance “due to the unusual nature and to ensure active monitoring".
For now, no additional human cases have surfaced. The Pan American Health Organization has been notified, and they commended Mexico for its vigilance. PAHO noted that this is the kind of zoonotic spillover that can occur when healthcare access is limited and awareness is low in certain areas. They support Mexico’s steps to reinforce the screwworm barrier at the Guatemala border, likely through continued sterile fly releases if necessary.
Veterinarians remind colleagues that Mexico still has a Screwworm Eradication Program that monitors and responds to any incursions. The program maintains traps and does periodic sterile fly drops along the Isthmus of Tehuantepec as a buffer. After this event, one can expect an intensification of those efforts.
Overall, while tragic, this isolated human case doesn’t indicate a widespread return of screwworm. It does, however, serve as a cautionary tale about complacency. The Ministry’s advice to the public is clear: keep wounds clean and covered, seek medical care for any maggot-infested lesion, and take care of animal wounds. They specifically mention to farmers that any case of maggots in a wound should be reported, as it could be the dangerous screwworm, not just common blowfly larvae.
As word of the case spreads, older farmers in Campeche recall the 1960s when screwworm was common and would devastate cattle herds. Many express hope it’s not returning. “We trust the government’s program,” said Don Eusebio, an 82-year-old rancher. “They eliminated gusano barrenador before, and they’ll keep it away now.” Gusano barrenador is Spanish for screwworm, literally “drilling worm.”
In summary, Mexican health authorities confirm the first recorded human screwworm death in Mexico, an extremely rare event, and are taking preventive measures to ensure it remains an isolated incident.
