Breaking the Cycle

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Breaking the Cycle
Though often overshadowed by the specter of AIDS, malaria remains a deadly menace in Africa. The U.S. Army and its partners have been trying to develop a vaccine for decades, but is this a battle they can win?

The six visitors who didn't get the vaccine are referred to as "control" subjects, aware that they are certain to get malaria if all is working right. But the group of vaccinated volunteers has the more jittery participants. Seated at a table, a woman is waving a hand in front of her hot eyes, trying to fight off tears. A paper cup has been brought out from behind door seven and placed on the table in front of her. Five infected anopheles are in the cup, which is covered with a tight mesh so the mosquitoes can't escape. They fly around the cup and press up against the mesh, bumping it repeatedly. The Army researchers theorize that the excited mosquitoes have smelled the carbon dioxide from the woman's exhalations. The scent of carbon dioxide is like a dinner bell. The woman is now supposed to put her arm over the mesh, enabling the mosquitoes to bite her from the other side. "Oh, gosh," she groans in a quavering voice. "Oh."

Gray Heppner says softly: "It's okay if you're having second thoughts. We have plenty of volunteers."

But a fellow volunteer, a blond nursing student at Montgomery College named Samantha Nolte, urges the woman not to quit. She has put her own arm over a cup and allowed the mosquitoes to start biting. "Just don't think about it," Nolte tells her. "Just do it."

At the researchers' request, Nolte has placed a blue dish towel over her arm. Mosquitoes like to feed when the sun goes down, and the towel will create the illusion that it's dark -- and time to eat. Nolte laughs. "I can feel them," she says to the other woman. "It's no big deal."

"God, I gotta get to work, I gotta get to work ," the other woman barks. She lowers her arm onto the cup. "Just bite me, and let's get this over with," she says, trembling.

Nolte grins. The mosquitoes are still feasting on her. "They just feel like little scratches, like tiny needles," she says, an apt description, because a mosquito "bite" is merely a euphemism. The mosquitoes have actually pierced her skin with their needle-like stylets, a sting, just before injecting mosquito saliva into Nolte to thin her blood and make it easier to consume. In the process, the mosquitoes' salivary glands have released malaria parasites that have been in the glands since shortly after the mosquitoes themselves were infected from biting an infected host.

No mosquito is a born carrier of a malaria parasite. Across an ocean from the lab, the infected carrier that bedevils the anopheles is not another insect but a bitten African or Asian person carrying the malaria parasite. Here, in Silver Spring, the host infecting the mosquitoes was an artificial membrane filled with blood purposely tainted by the researchers with malaria parasites. But whether in a Maryland lab or in Africa, the transmission of the parasite is a perfect circle in which a mosquito infects a human, who infects the next mosquito and so on, the cycle never ending. Only female mosquitoes bite people, needing the protein from human blood to lay eggs (male mosquitoes live off such things as the sap of trees). When a female anopheles gets malaria, she generally lays fewer eggs and flies more erratically than her uninfected sisters.

But there is one thing an infected mosquito does superbly: transmit the parasite to humans. In this moment, Samantha Nolte has probably been infected with from one to about 100 parasites from each of the five mosquitoes that has bitten her. To make certain that the insects in her cup are carriers, researchers lop off the heads of each mosquito with tweezers, examining the salivary glands under microscopes. In a few minutes, they pass the news on to Nolte: Yes, they've found parasites.

"That wasn't bad at all," Nolte says. "I feel great."

If she does contract malaria, the symptoms won't appear for at least a week. But already the parasites are active inside her, single-cell organisms fighting to stay alive.

Nolte, whose fiance has joined her as a participant, has been moved by stories she heard about the suffering caused by malaria from fellow nursing students, many of whom have emigrated from Africa. "I think it would be great to be part of history, part of something that stopped a disease that has killed so many people," Nolte says. And it doesn't hurt, she adds, that the trial will be paying her $100 daily for as long as the nurses draw her blood each morning and it shows no parasites.

Matt Randall, a doctoral student in comparative politics at Georgetown University, likes the money, too, though he says he is principally motivated by intellectual curiosity. "How many people get to say they're involved in something that could produce a breakthrough of this magnitude?" he asks.