The United States has temporarily closed its southern border to livestock imports as it battles a growing threat, the New World screwworm fly, a flesh-eating parasite that has moved further north in Mexico than expected.
According to the U.S. Department of Agriculture (USDA), the parasite poses a serious danger to the country’s cattle industry. Female screwworm flies lay eggs in open wounds of warm-blooded animals. Unlike most fly larvae, their maggots feed on live flesh, which can lead to severe injuries or death in livestock.
Why is the US worried?
The USDA fears that if the parasite reaches Texas, it could cause massive economic damage, similar to what happened decades ago. The fly was largely wiped out in the 1970s through a special program where sterile male flies were bred and released. When these sterile flies mated with females, their eggs failed to hatch, reducing the population over time.
The pest had been contained to Panama for years until it was found in southern Mexico late last year. Most recently, a new infestation was found about 370 miles (595 kilometres) from the Texas border, much further north than previously recorded.
What is the US doing about it?
On Wednesday, USDA Secretary Brooke Rollins announced that the U.S. would again tighten its border to prevent the pest from entering. "Thanks to aggressive monitoring, we have been able to take quick and decisive action to respond to the spread of this deadly pest," Rollins said in a statement.
The U.S. is planning to spend nearly $30 million to build new facilities for breeding and releasing sterile flies. The plan includes a new fly factory in southern Mexico, set to open by July 2026, and a holding site in southern Texas to store sterile flies from Panama for rapid deployment if needed.
How is Mexico responding?
Mexican President Claudia Sheinbaum criticised the border closure, calling it “totally exaggerated.” She said Mexico is following all the right protocols and is working hard to control the situation.
Mexican authorities said there were 392 infected animals as of this week, a drop of nearly 19% since June 24. They believe the issue is under control.
U.S. lawmakers are also urging quicker action. On Thursday, Reps. Tony Gonzalez of Texas and Kat Cammack of Florida asked the Trump administration to approve existing anti-parasite treatments for livestock, saying current labelling rules are slowing down the response.
If the fly population continues to grow, the U.S. may begin aerially releasing millions of sterile flies along the southern border as part of a long-term plan to stop the parasite in its tracks.
Inputs from agencies
According to the U.S. Department of Agriculture (USDA), the parasite poses a serious danger to the country’s cattle industry. Female screwworm flies lay eggs in open wounds of warm-blooded animals. Unlike most fly larvae, their maggots feed on live flesh, which can lead to severe injuries or death in livestock.
Why is the US worried?
The USDA fears that if the parasite reaches Texas, it could cause massive economic damage, similar to what happened decades ago. The fly was largely wiped out in the 1970s through a special program where sterile male flies were bred and released. When these sterile flies mated with females, their eggs failed to hatch, reducing the population over time.
The pest had been contained to Panama for years until it was found in southern Mexico late last year. Most recently, a new infestation was found about 370 miles (595 kilometres) from the Texas border, much further north than previously recorded.
What is the US doing about it?
On Wednesday, USDA Secretary Brooke Rollins announced that the U.S. would again tighten its border to prevent the pest from entering. "Thanks to aggressive monitoring, we have been able to take quick and decisive action to respond to the spread of this deadly pest," Rollins said in a statement.
The U.S. is planning to spend nearly $30 million to build new facilities for breeding and releasing sterile flies. The plan includes a new fly factory in southern Mexico, set to open by July 2026, and a holding site in southern Texas to store sterile flies from Panama for rapid deployment if needed.
How is Mexico responding?
Mexican President Claudia Sheinbaum criticised the border closure, calling it “totally exaggerated.” She said Mexico is following all the right protocols and is working hard to control the situation.
Mexican authorities said there were 392 infected animals as of this week, a drop of nearly 19% since June 24. They believe the issue is under control.
U.S. lawmakers are also urging quicker action. On Thursday, Reps. Tony Gonzalez of Texas and Kat Cammack of Florida asked the Trump administration to approve existing anti-parasite treatments for livestock, saying current labelling rules are slowing down the response.
If the fly population continues to grow, the U.S. may begin aerially releasing millions of sterile flies along the southern border as part of a long-term plan to stop the parasite in its tracks.
Inputs from agencies
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