In what's being called a breakthrough in the war on malaria, an international team of scientists has discovered that a mutation that makes parasites resistant to a key antimalarial drug winds up killing them.

Worries over the spread of resistance to the drug atovaquone -- which is noted for its safety and effectiveness even in children and pregnant women -- have significantly limited its use. But the discovery suggests that atovaquone could be used more broadly, and could dramatically enhance efforts to treat malaria, a parasitic disease that kills more than 400,000 people a year.

The research, conducted by scientists in Australia, Indonesia, Japan and the U.S., involved billions of malaria parasites and thousands of mosquitoes. When a mosquito bites someone infected with malaria, the mosquito becomes infected with microscopic malaria parasites -- which it then spreads to other people.

While some parasites develop a resistance to antimalarial drugs, the new study showed that the mutation that makes them resistant to atovaquone functions as a sort of "genetic time bomb" that eventually kills them inside mosquitoes' bodies by interfering with the production of energy the parasites need for growth.

"The resistant parasites die before they can infect another person," Christopher D. Goodman of the University of Melbourne, a member of the research team, told The Huffington Post in an email. "The atovaquone resistance dies with them, so new people can't be infected with the atovaquone-resistant parasites and resistance to this drug can't spread through the population."

University of Melbourne Mosquitoes during a "blood feed" in the laboratory.

"These results are very exciting because the spread of drug resistance is currently destroying our ability to control malaria," Geoffrey McFadden, a professor at the University of Melbourne in Australia and a member of the research team, said in a statement. "We now understand the particular genetic mutation that gave rise to drug resistance in some malaria parasite populations and how it eventually kills them in the mosquito."

Other malaria experts who were not involved in the research shared McFadden's excitement.

Laura Kirkman, assistant professor of medicine at Weill Cornell Medical College in New York City, called the research "interesting and remarkable" in an email to HuffPost. "We know there is drug resistance to all antimalarials currently in use," she wrote, "but this is the first example of resistant parasites that are also incapable of being transmitted by the mosquito to other human hosts."

"What's important is that this is the first finding of drug resistance that apparently can't be transmitted or spread -- a persistent problem with other antimalarial drugs," Sarah Hochman, an epidemiologist at NYU Langone Medical Center in New York City, said in an email.

In addition to encouraging wider use of atovaquone, the researchers said the finding could point the way toward the development of new malaria drugs, including less expensive, generic forms of atovaquone.

But before any of that can happen, the researchers need to do more work.

“Our next challenge will be to look for any spread of this drug resistance in field settings such as Kenya and Zambia," McFadden said.

A paper describing the research was published April 15 in the journal Science.