America is planning a war on screwworms. There are a lot more flies involved

A meat parasite that poses a major threat to livestock returned to the United States 60 years later. This week, the United States Department of Agriculture confirmed that a young cow in southern Texas found a new world spiral.

Spiral worms were eliminated in the United States in 1966 and re-emerged in south to Panama in 2006, and recently in Mexico, making it likely that they would eventually re-enter the country, with models showing that they could arrive as early as the summer of 2025. It took a little longer, but the rotor has arrived. In order to stop the outbreak, officials are deploying an effective technology: the release of a large number of adult spiral flies.

When a female flies lay eggs in open wounds or other parts of the body of a temperate animal, a spiral infection occurs. When the eggs hatch, maggots emerge and feed on living tissues, and become flies. When they are adults, they don't bite or eat meat. Scientists in the 1930s and 1940s believed that if we could stop female fruit flies from breeding, we could break the cycle. At that time, the New World Spirals killed hundreds of thousands of cattle each year, most of them in the south and south-west of the United States.

In the 1950s, researchers in the United States Department of Agriculture made a breakthrough by irradiating and infertility the male spiral. When released to the infected area, sterile male insects mate with wild female insects and produce unviable eggs. No offspring are born and the population is drastically reduced. This technology, known as sterile insects, was first successfully used on Curaçao, off the coast of Venezuela. It took only seven weeks to eliminate the pest, an effort that saved the island ' s flock, which was an important source of food.

The technology takes advantage of the fact that the female new world spiral flies mate only once in their lifetime. “Insect infertility is probably the most convincing example of a fully successful biological control mechanism,” said Sally Denota, Associate Professor of Veterinary Medicine, University of Florida. “The life cycle has stopped. No offspring. That was very successful.”

For many years, the dense rain forest between Panama and Colombia, known as the “Dalien Canyon”, has served as a biological barrier, where infertility flies have been released to prevent the spread of the rotors to the north. But insects started breaking this barrier in 2022.

In order to prevent an outbreak in southern Texas, the United States Department of Agriculture blocked approximately 12 miles around infected calves and targeted the release of sterile fly from trucks. In addition to this, 4 million flies are dropped on the area every week. It is expected that the fly will move north in February, and the Agency will shift the focus of the weekly dispersal of 100 million sterile flies to areas along the United States-Mur border.

The United States Secretary of Agriculture, Brooke Rawlings, stated at the House of Representatives Committee on Agriculture meeting on Thursday: “While this development poses a serious threat to our livestock and wildlife, it does not surprise us.”

She said she needed about 400 million flies a week to repel the spirine. Currently, United States factories in Panama produce only about 100 million flies a week.

In Mexico, an insect infertility plant was closed in 2012, but the United States Department of Agriculture is investing $21 million to assist in the renovation and rehabilitation of an existing fruit fly factory in Metapa, Mexico, which can produce an additional 6 to 100 million fruitless flies per week. According to the United States Department of Agriculture, the facility is expected to be operational this summer.

The Agency also rapidly advanced the $750 million sterile fly facility at the Mor Air Force Base near the Mexican border in Edinburgh, Texas. The facility will not be operational until November 2027.

Spirals are not infected with meat, fruit, vegetables or other sources of food, but they are infected with humans. According to the United States Centers for Disease Control and Prevention, there have been at least 2,070 cases of human rotors in Mexico and Central America since 2023.

Denota stated that she had no doubt that the United States would again eradicate the virus, but she said that, at the same time, there might be more cases. "A female fly can produce hundreds to thousands of eggs at once," she said. “They are able to travel to the next location and the next host, and this is unlikely to be the only case.”