The screwworm is one of those creatures that seems to exist simply to bring misery to those around it. Though seemingly just a normal everyday house fly as an adult, the baby stage of this bastard is particularly horrifying. While most baby flies tend to spend their formative years growing up in piles of shit and rotting carcasses, the screwworm larvae for some reason developed the odd evolutionary quirk of only being able to survive by eating living flesh. To accomplish this, the adults lay their eggs in open wounds, the eggs hatch, and voila, the host starts to get eaten alive, which as you can probably guess is not all that great.
Though endemic to most of the Americas, prior to the 1930’s screwworms were commonly only found in the southwestern United States, the deserts of the region creating a natural barrier to spreading further. However, by the 1930’s, growth in long distance interstate commerce in agriculture resulted in the screwworm getting spread into the southeastern United States with a couple of shipments of imported cattle. Rather enjoying the new wetter climate they found themselves in, the screwworms went gang busters, killing countless livestock and various wildlife critters. The people living in the southeast, not all that happy with this development, demanded government action. This being the era of the Great Depression and the New Deal, the government responded by sending out scores of random formerly unemployed people to quarantine infected animals, burn animal carcasses, and to try and make livestock ranges and pastures baby proof so that animals wouldn’t get injured. It worked about as well as you can imagine.
By the 1950’s, screwworms were a serious problem that was growing worse. A series of mild winters had resulted in them moving as far north as South Dakota, and the country no longer had a ready supply of unemployed people to throw at the problem. It was at this point that a USDA scientist named Raymond Bushland entered the fray. A bit of an outside the box thinker, Ray came up with the idea of zapping the screwworms with a small dose of radiation, because in the 1950’s a small dose of radiation was the go to for any scientist looking for new and novel ways of doing things. Rather than trying to create a team of super screwworms, as the strategy might suggest, Ray’s goal was to find the right dosage to make the male screwworms sterile without killing them. His plan was to raise sterile screwworms in his laboratory, then release them into the wild, thus denying countless fertile male screwworms from getting their nasty on, lowering the screwworm population over time. Now today this might sound like some kind of mad scientist plot, but back then people just thought bigger when it came to such things. Ray’s idea was first tested out in 1954 on the small Caribbean island of Curacao. In less than a year the screwworm was eradicated.
With Ray’s idea proven to be effective, the USDA geared up for all out war in the United States. The campaign began in Florida in 1957. The government built a massive fly breeding facility in Orlando, which pumped out millions of sterile screwworms, which were then dropped on a weekly basis across the state throughout the summer via airplanes. By the next year, the program was expanded to cover the whole of the southeastern United States, with success declared by 1960. With the southeast cleared, the intrepid scientists of the USDA decided to attack the screwworm on its own turf. New sterile fly factories were built in Texas, and by 1966, the United States was declared screwworm free. However, this victory was short lived, for the screwworm was still very much a thing in Mexico. To keep the screwworm from coming north, the USDA tried to create a barrier of sterile flies some 300 miles wide along the border. However, this proved less than possible given the border was some 2,000 miles long, and in 1972 a major outbreak made its way clear north to Oklahoma. Not willing to admit defeat, the USDA began funding a sterile fly program in Mexico, steadily pushing its way south and largely eradicating the pest in the country by 1985. However, the USDA was not done yet. Buoyed by its victory, the USDA began eradication campaigns across Central America, clearing out countries one by one. By 1995, screwworms had largely ceased to exist north of the Panama Canal.
Unfortunately for the USDA, this is where their campaign came to an end. Mexico had been more than happy to get rid of screwworms, and so had been fully onboard with the whole thing. As for Central American nations, their relationship with the U.S. was similar to that of children to a drunken stepfather. They mostly went along with things in hopes that Uncle Sam didn’t slap them around. The same could not be said of the nations of South America, who much preferred trying to prove they weren’t afraid of the U.S. by flipping it the bird from a safe distance. As a result, USDA attempts to eradicate screwworms south of Panama met with little success. Admitting defeat, the USDA shifted to a containment strategy, annually air dropping millions of sterile screwworms along the Panama Canal in order to keep the screwworm from making its way north. This program continues to this day.