The New World screwworm is a parasite the size of a housefly that eats living flesh. It was eradicated from the United States in the 1960s. Now it is back, and the weapon being used against it is as elegant as it is strange: millions of sterile flies.
The technique, developed by American entomologists in the 1950s, works by overwhelming wild screwworm populations with laboratory-raised males sterilised by radiation. When wild females mate with sterile males, they lay eggs that never hatch. The population crashes.
It is birth control as pest control, and it worked. The US declared eradication in 1966, and the barrier held for decades as sterile flies were released along the Mexico border.
Why it is back
The parasite has surged north from Central America through Mexico, breaching the biological barrier. This week, the USDA confirmed the first detection in US wildlife, an elk in Pecos County, Texas, and a beef cow in New Mexico’s Otero County.
Bangladesh’s measles vaccination drive shows another eradication effort under pressure. For Texas ranchers, the stakes are immediate: the state’s herd is the nation’s largest, and an outbreak would be devastating.
The science of the fightback
The USDA is releasing sterile flies in Central Texas, re-establishing the barrier. The method is proven but slow; it requires sustained releases over vast areas. Reuters has the details of the current operation, and the question is whether the barrier can be rebuilt faster than the parasite advances.
Eradication is not a victory. It is a maintenance contract.
