Key points
- Patient infected after travel to El Salvador
- Livestock sector alarmed by parasite spread
- US halts cattle imports from Mexico
ISLAMABAD: The United States Department of Health and Human Services (HHS) has reported the first human case of travel-related New World screwworm in the United States, a flesh-eating parasite rarely seen in people.
Exclusive: First human screwworm case in US traced to person in Maryland who traveled from Guatemala, sources say https://t.co/75HRPeSsfs https://t.co/75HRPeSsfs
— Reuters (@Reuters) August 24, 2025
The patient, who had recently returned from El Salvador, was confirmed to be infected on 4 August, following investigation by the Maryland Department of Health and the US Centres for Disease Control and Prevention (CDC), according to Reuters.
However, earlier reports from beef industry sources had linked the case to a traveller from Guatemala, a discrepancy the HHS did not clarify.
Authorities maintain that the risk to public health is minimal, and no animal cases have been reported in the US this year. Still, the incident has alarmed cattle ranchers and livestock traders, particularly given the pest’s northward movement from Central America.
Preventing potential outbreaks
Screwworms are flies whose females lay eggs in open wounds of warm-blooded animals. When hatched, the larvae burrow into flesh, potentially causing death if untreated. Although rarely affecting humans, treatment involves removing hundreds of larvae and thoroughly disinfecting the wounds.
The US Department of Health and Human Services has reported the first human case in the United States of travel-associated New World screwworm, a flesh-eating parasite, from an outbreak-affected country https://t.co/UDfTASPPe2
— RTÉ News (@rtenews) August 25, 2025
The confirmation comes amid increased concern in the US livestock sector. Agriculture Secretary Brooke Rollins recently announced plans to build a sterile screwworm fly facility in Texas to prevent potential outbreaks.
The USDA estimates that a serious outbreak could cost the Texas economy up to $1.8 billion in cattle losses and associated expenses.
Halting livestock imports
The US has already halted livestock imports from parts of Mexico, where screwworms have been spreading northward. Mexico is constructing a £40 million sterile fly facility to combat the pest, while the only current operating plant, located in Panama, can produce up to 100 million sterile flies weekly—well below the estimated 500 million needed.
Not even 10 days ago, Secretary Rollins hosted a press conference in Texas assuring the public that the last detected NewWorld Screwworm case was detected “370 miles away from our border”
About 3 days later there were leaked emails confirming a HUMAN INFESTATION CASE in the…
— Meriwether Farms (@MeriwetherFarms) August 25, 2025
The US cattle herd is currently at its lowest level in 70 years, pushing prices to record highs. The lack of transparency over the human screwworm case has drawn criticism from state vets and industry stakeholders, who say they were informed late and had to press for information from federal authorities.
Screwworms were previously eradicated in the US during the 1960s using sterile insect techniques. Concerns are mounting that the current spread, if not swiftly addressed, could undo decades of progress.
