Researchers plot the death of the malaria parasite

This week, the carpeted halls of the Philadelphia Marriott echoed with a patois of West African French, Liverpudlian English and Brazilian Portuguese as researchers from around the globe converged for the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH).

The convention covers a wide range of tropical diseases, but malaria got the lion's share of attention.

Big scientific conventions are odd social gatherings. I like to think of them as theatrical productions. In this one, malaria was the ghost attendee, hovering just offstage with a plastic "P. Falciparum" name tag slung around his bulging neck.

Meanwhile, onstage at the convention, doctors, researchers and scientists plotted Mr. Falciparum's death and recounted war stories about all the attempts to exterminate him.

There were sessions on new malaria drugs, old malaria drugs, potential vaccines and everything you could ever want to know about Anopheles mosquito's "species diversity, behavior and sporozoite rates in six states in Nigeria."

There were entire sessions devoted to the ability of plasmodium parasites to hide in "asymptomatic reservoirs." Researchers explained how malaria parasites hang out in healthy people and then pounce on unsuspecting children. This hiding-among-the-healthy trick makes it incredibly difficult to finish off malaria in a particular area.

Other sessions looked at how malaria is becoming immune to artemisinin-based drugs — the latest and best medicines commercially available to fight it.

Roch Dabire from the Institut de Recherche en Sciences de la Sante, in Bobo-Dioulasso, Burkina Faso, described how malaria-carrying mosquitoes now shrug off industrial insecticides.

"In West Africa, we have a lot of problems with mosquito resistance to insecticide," Dabire said. He's working on a study that uses ivermectin, a drug usually used to treat roundworm parasites, to kill malaria-carrying mosquitoes.

Dabire and his colleagues noticed that right after mass deworming programs in villages, mosquitoes were dropping dead. So now they're trying to give the deworming medicine continuously during the rainy (heavy malaria) season. Early results are promising, he said; in villages blanketed with ivermectin, fewer kids are coming down with malaria.

Dabire conceded that it's sort of a backdoor way to attack the disease. "We need to have alternatives," he said.

"I'm not claiming this is a silver bullet," added his colleague Brian Foy from Colorado State University. "The only way you are going to control malaria and eliminate it is by a very large toolbox that is targeting the parasite in many different ways."

That toolbox keeps changing as the malaria parasites and the mosquitoes that harbor them become resistant to new drugs and insecticides.

The parasite is changing so much that old drugs that had become ineffective against it are now lethal again. A researcher from Mozambique explained how quinine, a staple of malaria control in the past that lost its effectiveness, can now be effective again in some combination drug therapies. Scientists are also looking for new ways to revive primaquine, a malaria drug developed in the 1940s that had been a solid tool against the disease in the late 20th century.

"Malaria is always a big topic here," said Chris Plowe, this year's president of ASTMH. "When our society started more than a hundred years ago, it really was started around malaria, and it continues to be a big part of what we do."

Significant progress is being made. The mosquito-borne disease that killed, by most estimates, at least a million people a year 15 years ago now claims roughly 600,000 lives annually. That number continues to slide down.

Much of the American Society of Tropical Medicine and Hygiene convention focused on hard science around malaria and other tropical diseases. Take for instance Tuesday's session on "Rapid reorganization of the parasite plasma membrane induced by new classes of antimalarial drugs that disrupt NA+ homeostasis."

But there were moments that looked at the deep social and personal effects of this ancient killer.

Poet Cameron Conaway read a selection from his book Malaria Poems about a pregnant mother who lost her baby to malaria.

In bed when the cold cat curls

Around her like fog, it will be him,

And she will match her breath to his.

At a convention where you could get lost in PowerPoint presentations on the molecular structure of malaria drug candidates, Conaway's poems were a reminder of why all this science matters. Copyright 2019 NPR. To see more, visit https://www.npr.org.