Declining malaria deaths in Africa and progress toward an effective malaria vaccine are raising hopes the disease will soon be eradicated worldwide. But researchers at the annual meeting of the American Society of Tropical Medicine and Hygiene in Philadelphia, Pennsylvania, this week unveiled a new global malaria map that raises new concerns about the disease.
Just when health experts thought they were on the winning side in the battle against malaria, a disease that kills almost 800,000 people around the world each year, a once-minor strain of the malaria parasite has now emerged as a major public health threat.
And it is a far more complicated and deadly strain than the one being targeted by vaccine.
Malaria caused by Plasmodium vivax has long been considered more benign than the disease caused by the Plasmodium falciparum parasite, the kind prevalent across Africa. But the new global data show that's not true, says Peter Gething of Oxford University, who spoke to us via Skype.
“Plasmodium vivax is very, very important, a big global public health problem. It kills people at a much much higher rates than was previously thought and there [are] actually more people at risk of vivax globally than there are of [plasmodium] p. falciparum," he said.
Gething is the lead researcher on the Malaria Atlas Project, a new effort to monitor changes in the worldwide prevalence of malaria.
Gething says about 2.8 billion people are at risk from this new variety of malaria, and he adds that the tools for fighting the disease range from ineffectual to non-existent.
“[An] Important fact about vivax is, it is not a large public health problem in Africa, where falciparum is predominant. Vivax is an important problem in those parts of the world where the area is very populous, so it's a very significant problem, for example, in India, Indonesia, and throughout much of central and south East Asia," he said.
Experts in the field also note that control measures such as pesticide-coated bed nets are not as effective against the vivax parasites because the mosquitoes that carry them are more likely to bite their victims outside the house than inside.
"It [Plasmodium Vivax] can hibernate in people's livers and lay there dormant for months or even years. And when it’s in the liver that particular stage of parasite is not responsive to the normal bloodstream drugs that we use against falciparum. So, you can treat the person and they will recover, but you don’t cure the underlying infection," he said.
The best known drug against vivax-induced malaria is primaquine, but it requires a 14-day regimen that's hard to follow in many malaria-prone regions of the world. The drug also causes serious side effects in people with an inherited blood disorder. That is fairly common in regions where vivax is endemic. Research is underway on some promising new drugs to fight the vivax malaria parasite.