Cases of flesh-eating screwworm on the rise in Mexico

Mexico is facing a growing problem with a dangerous parasite called the New World screwworm. This flesh-eating bug is actually the larva of a fly, and it has been infesting more animals and even some people in recent weeks. According to government data, the number of cases has jumped by 53 percent in just four weeks leading up to mid-August. While screwworms mostly attack cattle, there have also been cases found in dogs, horses, sheep, and humans. Hospitals in the southern states of Campeche and Chiapas have treated dozens of people for screwworm infestations. The issue is not limited to Mexico. Recently, US health officials confirmed the first human case in a patient who had traveled from El Salvador. Screwworms were wiped out in the US in 1966 and in Mexico in 1991, thanks to a program that released sterile male flies to stop the bugs from reproducing. However, screwworms are still common in tropical and subtropical regions of Central and South America. The parasite has started spreading north again, with the first new case in Mexico reported in November 2024.

The female screwworm fly, known as Cochliomyia hominivorax, lays her eggs in open wounds or in moist areas like the nose, mouth, eyelids, ears, and genitals of warm-blooded animals. When the eggs hatch, the larvae burrow into the wound or membrane and feed on living flesh. This condition is called myiasis. If left untreated, myiasis can cause serious damage and even be fatal, as the larvae tear into tissue with their sharp mouth hooks. Health officials warn that while deaths from screwworms in humans are rare, people with other health problems and older adults should be especially careful. In July, an 86-year-old woman in Campeche died from skin cancer that got worse because of a screwworm infestation. People who work with livestock or live in rural areas where infected animals are present are most at risk.

The US Centers for Disease Control and Prevention advises anyone who has visited areas with screwworms to watch for symptoms like unexplained skin sores, feeling larvae moving in a wound or in the nose, mouth, or eyes, and seeing maggots in an open sore. Experts say prevention is very important. When visiting rural areas in affected regions, people should keep any wounds clean and covered and use insect repellent. If someone suspects they have screwworms, they should seek medical help right away. Scientists are also studying screwworm larvae collected from infected cows to learn more about how to stop the spread of this dangerous parasite. The rise in screwworm cases is a serious concern for both animal and human health in Mexico and nearby countries.