Humans have had to live with malaria for a long time. So long, in fact, that we even see changes in our genome that protect us from the disease.
"Sickle cell anemia probably emerged in human populations approximately ten to twelve thousand years ago. And this occurred coincidental with the change in lifestyle and agricultural settlements. So there was enough population densities of people that mix with population densities of mosquitos," Jim Kazura said.
Two copies of the sickle cell gene give you malformed blood cells, or sickle cell anemia. But, one copy of the gene makes your blood cells just weird enough that, 90% of the time, the malaria parasite can’t invade them. Jim Kazura is professor in the Center for Global Health and Diseases at Case Western Reserve University. He studies factors affecting naturally-occurring immunity against Malaria, particularly in young children.
"People have done studies on children with sickle cell anemia in sub-Saharan Africa now - forty to fifty percent will be dead by the time they're three years old. The trade off from that, from an evolutionary perspective, is if you only have a single copy, you are not ill, but it protects you against death from malaria. So it can, it shows you what a powerful influence malaria has had in terms of the evolution of our own species."
The malaria parasite is so good at making us sick, even killing us, you’d think that’s what it wanted. But, figuring out that that is not the case may be the key to eliminating it.
“The parasite doesn't want to kill its host, the mammalian host, because you have to have people with blood stage infections so the mosquito can pick it up,” Jim Kazura said.
“We see a lot of adults in sub-Saharan Africa who have a low grade infection in their bloodstream, but they're not sick. They're walking around.”
Kazura is interested in finding out what allows the malaria parasite to reach the “Goldilocks” stage of living in a human, without making them sick.
“If we understand that, we might be able to boost that response enough to have their immune response eliminate those low-grade asymptomatic infections,” Kazura said. “Because ultimately that’s what will be needed to eradicate malaria, because the mosquitos will no longer have a reservoir to continue transmission.”
Most malaria medication is aimed at making sick people feel better, but if Kazura can figure out how to eliminate the disease in people who feel well, the malaria parasite will have fewer and fewer places to live, allowing us to ultimately eliminate it completely.