NDOYENNE, Senegal — The Senegalese farmer is certain: Atomic birth control saved his cows.

Arouna Sow, 55, worried his family would starve when the animals got sick three years ago. Their eyes grew teary, their fur clumped off, their ribs poked out, their milk dried up — all because of the tsetse fly's toxic bite, which kills an estimated 3 million livestock annually in sub-Saharan Africa.

Farmers here used to count on losing pounds of valuable beef to the fingernail-size pest. Then veterinarians in the West African country teamed up with researchers in Austria who work on a project funded entirely by the United States.

"I can feedmykids and afford health insurance," said Sow, a father of 15. "I don't understand the science, but I know it's working."

Senegal, a former French colony hugging the Atlantic Ocean, has sought to wipe out the bloodsucking disease spreaders for more than a decade. Farmers say relief has finally arrived in the country's western Niayes zone, where scientists have eradicated 99 percent of tsetse flies by sterilizing the males with gamma rays.

The United States has poured about $5 million into this effort, which has reduced the number of trypanosomiasis cases down to nearly zero.

It's part of a broader push by the U.S. government to harness nuclear energy for good that has stayed on track even as the Trump administration has sought to slash foreign aid elsewhere.

Farmer income in Niayes is expected to jump by 30 percent, officials say, as more cows survive at a healthy weight. And farmers can now afford to buy hundreds of European dairy cows, which produce 20 times as much milk than native breeds.

The fortune reversal sprouts from a global collaboration at the intersection of agriculture and nuclear technology.

Since 2010, America has funneled roughly $379 million to Senegal's partner in the tsetse fly fight: the International Atomic Energy Agency, a global body that develops benevolent uses for destructive forces.

It's unclear whether the investment leads to financial gain for the American side.

Jeffrey Eberhardt, whom President Donald Trump has nominated to serve as his special representative for nuclear nonproliferation, said in May that the United States wants to "expand the benefits of peaceful nuclear uses" and expressed "a firm commitment to continuing this legacy."

The peaceful use in Senegal is called nuclear insect sterilization.

First, scientists hatch thousands of tsetse flies in an artificial habitat about 870 miles away, in the West African nation of Burkina Faso.

Next, they send the bugs to the lab in Seibersdorf, Austria, where researchers place them in tiny ionization chambers and blast them with gamma rays, rendering the males unable to pass on a healthy seed.

Finally, they chill the flies to sleep — broken wings from panicked thrashing would sabotage the mission — before tucking them into biodegradable paper boxes and shipping them to Senegal.

The sterilized males, raised on blood that does not contain disease, compete with natives for partners. Females lay fewer and fewer viable eggs.

"It's basically birth control," said Marc Vreysen, head of the IAEA's pest control lab.

This technique emerged in Africa two decades ago on the Tanzanian island of Zanzibar. Tanzanian scientists, with outside support, experimented with nuclear sterilization. The island's flies vanished after three years.

Word spread to Senegal, which rallied the IAEA for help in 2005.

On a May day in Niayes, farmers walk without swatting away insects. Baobab trees offer shade to donkeys and goats. A brown dog trots between healthy indigenous cows that have long, sharp horns and are mainly raised for their meat.

Nearby, black and white dairy cows from Europe huddle together. A banner overhead celebrates the "foreign" cattle. Unlike the native animals, they lack natural resistance to the tsetse fly's infectious nip.

"They could not have survived with the tsetse flies," said veterinarian Mamadou Demba, who joined researchers in Niayes on a search for remaining evidence of the pest. So far, he said, so good.

About 1,200 dairy cows graze in the region — quadruple the number that existed here five years ago.

This success has caught the attention of Burkina Faso, Uganda and South Africa, which have launched their own programs, IAEA officials say.

On a recent afternoon, a yellow helicopter approaches and drops boxes of sterilized flies from the lab in Austria. The containers land in trees and fields.

Researchers rush over to one and pick it up. Flies crawl around inside, apparently dazed from their overseas journey. Others spill out from dime-shaped holes.

Everyone watches as they buzz off in search of an increasingly scarce mate.

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