Screwworm Battle Needs More Flies and Collaboration, IAEA Says

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(Bloomberg) — A key international nuclear lab helping to eradicate the New World screwworm says more sterile flies and better coordination with southern neighbors is needed to prevent the deadly parasite from spreading across North America.

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The Vienna-based International Atomic Energy Agency said Thursday it’s coordinating a new project to stem the outbreak threatening billions of dollars in damages for ranchers in the US. The coordinated research project aims to improve tools for detecting and combating the parasitic fly, and comes as growing cases in Texas add urgency to containment efforts.

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The agency was part of efforts over four decades to drive the pest out of North America, introducing sterile-insect techniques. The method involves rearing and irradiating billions of male flies inside specialized bug factories so they become infertile. When released into the wild, they mate with females without producing offspring, gradually curbing hatching rates and reducing the overall population. 

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This time around, countries aren’t currently producing enough sterile flies to suppress the pest, according to Rui Cardoso Pereira, who heads the IAEA’s Austrian laboratory that deals with screwworm outbreaks. The US is racing to rebuild capacity after decades of eradication left the region with too few facilities to respond to the pest’s return.

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“The economic impact is huge,” said Pereira. A lack of sterilization factories is “the main bottleneck” preventing scientists from containing the disease, he said. 

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Texas was producing about half a billion sterile flies a week when screwworm last infected cattle in the ’60s and ’70s.

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Only about 100 million flies are currently produced each week at a facility in Panama. A plant in Texas is expected to add another 300 million a week, but it won’t be in full operation until 2027. A third site under construction in Mexico could come online later this year, producing another 100 million flies a week.

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The outbreak also underscores the need for US collaboration with its southern neighbors, said Pereira, a Portuguese entomologist trained in the US. 

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“It took 40 years to clean up but only three years to come back,” he said, adding that scientists and farmers will have to “roll the carpet” down from the southern US border through the Panama Canal to ensure the New World screwworm is eradicated again.

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Climate change is compounding the spread, according to the IAEA, because longer warm seasons can increase reproduction further north. While cattle ranchers wait for sterile-insect production to ramp up, the agency wants to implement additional surveillance measures across Central America and Mexico. 

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“One of the problems today is that these Central American countries were without the fly for 30 or 40 years,” Pereira said. “The new vets don’t know the problem.”

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