Mexican agricultural authorities recently announced a confirmed case of New World screwworm in cattle within the northern state of Nuevo León. This alarming discovery represents the closest the flesh-eating parasite has come to the U.S.-Mexico border since its eradication from the United States in the 1960s. The re-emergence of this livestock menace in Mexico has been a growing concern over recent months.
The affected animal was an eight-month-old cow, part of a larger shipment of 100 cattle transported from an already impacted region in Mexico to a feedlot in Nuevo León. Fortunately, agricultural officials confirmed that only this single animal in the entire consignment was found to be carrying the parasitic infestation.
The detection site, Sabinas Hidalgo, a small city in Nuevo León, lies less than 70 miles from the U.S.-Mexico border. This proximity is particularly concerning given that the previous northernmost case, reported in July, was in Veracruz, eastern Mexico, a considerable 370 miles further south.
Following the detection, Mexico’s Secretary of Agriculture, Julio Berdegué, reassured the public via social media that the government is actively monitoring the situation and implementing joint measures coordinated with the American government. He confirmed a direct discussion with Brooke Rollins, the U.S. Secretary of Agriculture, regarding these urgent developments.
Mexican authorities emphasized their early detection of the infestation. They explained that screwworm flies deposit their eggs in open wounds. Upon hatching, the larvae burrow deep, consuming living tissue and causing severe harm. Once mature, these larvae fall to the ground, pupate in the soil, and eventually emerge as adult flies, continuing the cycle.
As a precautionary measure, the entire cattle shipment originating from Veracruz underwent rigorous inspection for any signs of wounds or maggots. Additionally, all animals received prophylactic treatment with ivermectin, a potent antiparasitic medication.
In a statement from the U.S. Department of Agriculture, Ms. Rollins characterized the screwworm detection as a ‘national security priority.’ She highlighted the support and resources the U.S. government has extended to Mexican officials to combat the parasite, reiterating the commitment to preventing its re-entry into the United States.
To curb the spread of the outbreak across Central America, the U.S. Department of Agriculture has implemented a strategy involving the mass production of sterile screwworm flies. The agency has invested millions in expanding sterile fly production at a Panamanian facility and bolstering public awareness and inspection checkpoints throughout Central America. Furthermore, this year saw an announcement of an additional nearly $30 million investment to upgrade a sterile fly production facility located near the Mexico-Guatemala border and establish a new dispersal site in Texas.
Since July, both the U.S. and Mexican governments have been rigorously monitoring thousands of fly traps strategically placed in border states. While no screwworm flies have been detected on either side to date, authorities remain committed to exploring and investing in innovative tools to combat this persistent parasite.
During her Monday news conference, Mexican President Claudia Sheinbaum disclosed that a U.S. Department of Agriculture team recently visited Mexico to assess the preventative measures being implemented. She stated that the team concluded Mexico is ‘doing everything in our power to prevent further contamination from the New World screwworm,’ and their official ruling is expected soon.
Following earlier detections in the Mexican states of Oaxaca and Veracruz this year, the U.S.D.A. had previously closed southern ports to livestock trade. In July, President Sheinbaum described the decision to halt cattle imports as ‘exaggerated’ after a lone case was found in Veracruz. Currently, American ports continue to restrict imports of Mexican cattle, bison, and horses.
President Sheinbaum reiterated that a crucial agreement with the U.S. government stipulates that border decisions regarding livestock trade would be based on objective technical indicators, rather than being discretionary. She concluded by noting that the U.S.D.A. team’s official report from their recent visit to Mexico is anticipated within a few days.