By Robert Fortner, special to Humanosphere
It seems like a no-brainer: Distribute insecticide-treated nets to poor countries most at risk from malaria and we can reduce the death toll of this major global killer.
And it has been a bit of no-brainer, but not always in a good way.
Since 2000, billions of dollars have been spent on a massive and multipronged anti-malaria effort supported by the World Health Organization, groups like Nothing But Nets, the Global Fund to Fight AIDS, TB and Malaria and other organizations. As a result, WHO says, malaria mortality has fallen by about 50 percent globally in the past 15 years.
But how certain are we of this success story, and what’s really driving it? Is it the hundreds of millions of bednets?
“That’s the million dollar question,” said Moses Kamya, speaking recently at the University of Washington’s Institute for Health Metrics and Evaluation (IHME) in Seattle.
Kamya is a professor of medicine at Makerere University in Uganda. He presented an unpublished study showing persistently high transmission and increasing incidence of malaria in rural Uganda despite universal bednet coverage and effective anti-malaria treatment.
Kamya findings suggest that some experts are quietly, sometimes reluctantly, beginning to dig deeper into the assumption that bednets are as effective as claimed.
Since 2002, about $11 billion has been spent on malaria interventions, with bednets a primary focus and media relations centerpiece. But the fight against malaria has been on many fronts – expanded access to treatment, insecticide spraying and other interventions. And the emphasis with the nets largely has been on measuring their successful distribution, not their impact on disease. No brainer.
For example, Rollback Malaria in 2011 announced that 1.1 million lives had been saved by anti-malaria efforts, based on a modelling study that attributed almost all (99 percent) lives saved to bednets. But not everyone believed the models. The Center for Global Development (CGD) left bednets out of the first edition of its “Millions Saved” list of interventions picked to demonstrate that scaled health programs can have a direct impact on saving lives. The 2014 second edition also pointedly excluded nets.
CGD distinguished “between the efficacy of an intervention and its effectiveness in delivery at scale.” Controlled trials might show efficacy but CGD wanted to see hard numbers, not model estimates that rose in proportion to the number of nets distributed.
Patrick Kachur, chief of the malaria branch at the Centers for Disease Control (CDC), has also called for “pivoting from tracking the delivery of commodities,” such as bednets and anti-malaria drugs, “to actually tracking the impact, tracking real numbers of cases and expanding the areas of the malaria endemic world where we can rely on actual reported cases and don’t have to model the impact on malaria.”
Even the normally cautious and skeptical gang of metricians at IHME were early advocates of the efficacy of the bed nets. A 2011 IHME study reported a 23 percent reduction in deaths attributable to the lifesaving benefit of nets. Although the paper only reported all-cause mortality, an IHME press release stretched further, asserting “researchers found clear evidence that bed nets reduce the number of child deaths from malaria.”
But in 2012, IHME published a headline-making analysis of global malaria mortality between 1980 and 2010 in the Lancet. It reported that bednets did not reduce adult deaths from malaria in Africa: “coverage of insecticide-treated bednets was not a statistically significant predictor of African adult malaria mortality.”
The paper was silent on the more important question of whether bednets saved children in Africa, who are most susceptible to malaria and the target of bednets. The omission went unnoticed at the Lancet. According to Executive Editor Richard Turner, “no reviewer of the Lancet paper asked specifically about a possible association between bednets and malaria mortality for children under 5 in Africa.”
The million dollar question wasn’t asked in 2012.
After hearing Kamya’s evidence, the audience in Seattle seemed to skirt around the elephant in the room, with oblique inquiries, for example: “What has been the reaction to your presentation?”
IHME chief Chris Murray wondered what would happen to “the energy behind bednets.” So I asked Kamya what seemed like the obvious question: Have bednets had been oversold?
“That is true,” he said. Kamya’s study is, of course limited to Uganda, but it provides real numbers and a glimpse at what may be the tip of an emerging iceberg. The bednets aren’t making as much of a difference as had been assumed.
Kemya’s study did find malaria incidence fell in the “peri-urban” site in the study, but he seemed unwilling to attribute the effect to nets because malaria incidence is correlated with socio-economic indicators that are better outside rural areas. He talked about construction, houses with screens. He also said malaria at the site was already declining before the nets came.
Uganda is third in the world for malaria cases and ninth for percentage of children infected with malaria at 30 percent, according to the 2014 World Malaria Report. Malaria deaths in the report assume bednets reduce malaria mortality rates by 55 percent in children under 5 years of age in sub-Saharan Africa. The World Malaria Report claims that 92 percent of 4.3 million lives saved between 2001 and 2013, were in children aged under 5 years in sub-Saharan Africa.
Presenting to IHME, a major producer of malaria estimates, Kemya spoke of covering “the entire country in bednets” to little effect. Kemya had yet to report his results to Uganda’s ministry of health. But he predicted: “I think they will be very discouraged that there’s no impact.”
Robert Fortner, based in Portland, Ore., is a science writer whose work has appeared in Scientific American, Ars Technica, and the Columbia Journalism Review. He is working on a book about Bill Gates, science and technology.