An outbreak of the flesh-eating New World screwworm (Cochliomyia hominivorax) has caused widespread devastation in Mexico and South America, with seven people dead and over 1,190 infected. The US Centers for Disease Control (CDC) has issued a warning to health workers about the northward spread of this deadly parasite.
The New World screwworm is a fly larva that feeds on the wounds and mucous membranes of warm-blooded animals, including cattle, horses, pigs, dogs, cats, and even humans. Without treatment, infections can be fatal, with the ability to kill a mature cow in just one week.
The CDC alert comes as there are currently 601 active animal cases in Mexico, with eight in Tamaulipas, a state that borders Texas. This has raised concerns about the potential spread of the screwworm into the United States, particularly in Texas, the largest cattle-producing state in the country.
In the 1960s, efforts were made to control the screwworm population by releasing sterile male flies that would mate with wild females and produce unfertilized eggs. This method, known as the ‘sterile insect technique’, along with chemical treatment of cattle and favorable weather conditions, led to the eradication of the screwworm in the US, Mexico, and parts of Central America by 1982.
However, in 2023, the screwworm breached the barrier created by sterile flies in Panama and resumed its northward spread, reaching Mexico by November 2024. The CDC attributes this resurgence to unregulated cattle movement, increased movement through the Darien Gap, and new areas of farming.
Climate change is also believed to be a contributing factor, with warmer temperatures expanding the screwworm’s range and boom period. Scientists warn that the parasite could pose a significant threat to the US cattle industry, with potential losses estimated at $1.8 billion.
While no infestations related to this outbreak have been reported in the US so far, the CDC is urging clinicians and health departments to be vigilant and follow their recommendations for case identification, reporting, specimen collection, diagnosis, and treatment of New World screwworm infections.
As the situation continues to evolve, it is crucial for health workers to stay informed and take necessary precautions to prevent the spread of this deadly parasite. The full CDC health advisory can be accessed for further guidance on how to address this concerning issue.
