The United States have fought a continuous air war against the new world screw worm for 70 years, a parasite that eats living animals: cow, pig, deer, dog, even human. (His scientific name, C. HominivoraxTranslates into “male-eater.”) Larves of the parasitic fly chew through meat, so that small notches are transformed into large, horrible wounds. But in the 1950s, the US Department of Agriculture laid the foundation For a continent-wide attack. Employees raised screw worms in factories, shot with radiation until they were sterile and left the sterile adult screwworms with millions – even hundreds of millions – over the US every week, then further south in Mexico, and eventually falling into the rest of North America.
The sterile flies passed to the wild populations of the continent in oblivion, and in 2006An invisible barrier was founded at the Daréén opening, the jungle that extends across the border of Panama-Colombia, to corder the screw-worm north from the south. The barrier, as I noticed when I reported Panama a few years ago, consisted of aircraft that releasing millions of sterile screwworms to rain over the Darién gap every week. This endless battle kept the threat of screwworms far from America.
But in 2022 the barrier was violated. Cases in Panama – usually in cattle – shoot from tens of a year to 1,000, despite constant drops of sterile flies. The parasite then started moving north, first slowly and then quickly in 2024, when I received alarmed e -mails from those who followed the situation in Central America. From this month, the parasite has been 1,600 miles advanced by eight countries to reach Oaxaca and Veracruz in MexicoWith 700 miles to go to the border with Texas. The US then shakes live-ratter import from Mexico.
After this latest news broke out, I spoke with Wayne Cockkell, a rancher in Texas who fears that the return from the screwworm to Texas is now a matter of whennot when. The anti-screwworm program cannot produce enough sterile flies to stop the rise of the parasite, let alone beat it back to Panama, Cockkell explained. He closely followed the outbreak as chairman of the Cattle-Health Committee for the Texas and Southwestern Cattle Raisers Association, which recently visits the sterile-fly factory. “There is now a feeling of fear from my side,” he told me.
At the age of 60 he is too young to remember screwworms himself, but he has heard the horror stories. Every cut, every scratch, every navel of a newborn calf threatened to become fatal in the pre-eradication era. If the parasite holds the US again, it can take decades to push screwworms back to Panama. After all, that is how long it took the first time. Decades of vigilance of screwworms have been undone in just two years.
You just have to look at a card to understand why the outbreak of the screwworm is now at an alarming bending point.
Midden -America has the shape of a funnel with a long, bumpy tail that reaches its thinnest point in Panama. In the past, the USDA helped to pay the extermination of screwworms to Panama from not pure altruism but economic pragmatism: setting up a 100-mile screw barrier is cheaper than creating a 2,000 Mile-Mexico border. Even after screwworms recently started to crawl the funnel’s tail, the anti-screwworm campaign had a last good chance of putting them in a narrow land length in southern Mexico-Daaara, the funnel becomes dramatically greater. It failed. The newest screwworm detections in Oaxaca and Veracruz are just outside the country length.
The wider the new front of the screwworm war grows, the more sterile screw worms are needed to stop the rise of the parasite. But the range is already overloaded. The flight factory in Panama has increased production from its usual 20 million flying a week to the maximum of 100 million, all of which are now distributed across Mexico. But aircraft fell 150 million flying a week over the Isthmus in Mexico during the first external campaign in the 1980s. And when the front was even further north in Mexico, a factory released so much 550 million flying Weekly to cover the huge area. That factory, as well as one in Texas, has long been closed.
The Texas and Southwestern Cattle Raisers Association asks the USDA to build a new sterile-fly plant in the US, a large enough to produce the hundreds of millions that may soon be needed. “We work closely with Mexico to restore a biological barrier and prevent further geographical spread,” wrote a USDA spokesperson in response to questions about the adequacy of sterile-fly production. “If the fly spreads geographically, we must re -evaluate the production capacity.” Various legislators in Texas recently have the Stop screwworms actwho instructs the USDA to open a new factory, but the entire process can take years. “The facility must start tomorrow,” said Cockkell.
The American cattle industry is not prepared for the return of the screwworm, he said, more reasons: certain drugs to treat screw -worm infection have no license in the US because they have been unnecessary for half a century. Ranches used 50 cowboys that have regularly inspected cattle, and now they may only have five. And routine industrial practices such as branding and earaging make the animals make vulnerable to screw -worm infection. To face the screwworm, the cattle industry will have to adapt quickly to a new normal. The parasite could propel the prices of beef, which are already high -row Due to drought, even higher.
How screwworms managed to make the barrier jump in 2022 is not completely clear. But in the years immediately, The Coronavirus Pandemie Allegedly, Supply Chain Snarls created in the Fly Factory in Panama and disturbed regular cattle inspections that could have dropped the alarm bells earlier. And the border between Panama and Colombia became much busier; The Darén-kloof, once a notoriously impenetrable jungle, became a popular route for migrants.
Yet the screwworm went relatively slowly through Panama and Costa Rica for the first few years. Then it hit Nicaragua and for only 10 weeks in 2024 it shot from the northern border of the country by Honduras and Guatemala to reach Mexico. This rapid rise was due to the illegal cattle trade, Jeremy Radachowsky, the director of Meso -Marikaans and the Western Caribbean of the Wildlife Conservation Society, told me. His organization has followed the practice in Central America, where 800,000 cattle per year are raised illegally in nature reserves and then smuggled by boat and truck to Mexico. This allowed the screwworm to spread much faster than it can fly. The line of new screwworms followed well -known smuggling routes, Radachowsky said. The constant northern movement of infected cattle could now make re -upranging more difficult. It’s like trying to empty a swimming pool when “the spigot is still open,” he said.
Decades of screw -worm -free existence mean that even farmers, whose means of existence are immediately affected, slowly recognize the growing emergency situation. “We were so successful that literally people had forgotten it,” said an American officer in Central America who is familiar with the situation (anonymous speaking because of delicate politics). Inspections, timely reports of infections and restrictions on cattle movements are important pieces of extermination, in addition to the release of sterile flies.
Over the years, scientists have also suggested more advanced ways to control the screwworm through genetics, although there is no ready for Prime Time. The USDA supported research by Max Scott, an entomologist at North Carolina State University, to create a male tension that could reduce the number of flies for spread, but the financing ended last summer. He also suggested using Gene Drives, a still controversial technique that can quickly ‘drive’ genetic material that makes women sterile in the wild population. The USDA was not interested, he told me. (A spokesperson says that the USDA “continues to investigate and investigate new tools”, including genetically manipulated male screwworms.) But he tackled a collaboration with scientists a few years ago in Uruguay Studying a genre drive for sterile screwworms.
Uruguay is interested because it has never been able to take advantage of the extermination of screwworm; The country is approximately halfway through South America, deep in screwworm area. A retired USDA scientist, Steven Skoda, told me that he and his colleagues used to dream of ‘a world that is completely free of screwworm’. But extermination has never been reached in South America, and now even the barrier that North -America protects is no longer intact. The campaign to push screwworms from southern Mexico – focused where the parasite is now – lasted 21 years to the southern edge of Panama. The way things go, said Cockkell, some of his old colleagues in Panama may not see in their country in their country being rejected in their country.
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