Mathematical model projects potential impact of current tools fighting malaria in Africa

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Aug 16 2010

Current tools for combating malaria, such as artemisinin-based combination therapy (ACT) and increasing coverage of long-lasting insecticide treated nets (LLINs) insecticide-treated bednets (ITN) "could dramatically reduce the burden of malignant malaria on parts of Africa if a comprehensive, sustained intervention programme were in place," according to a study published this week in PLoS Medicine, CORDIS News reports.

"According to the study, half of the world's population is at risk of malaria infection, and every year it claims the lives of nearly 1 million people in sub-Saharan Africa," the news service adds. "Plasmodium falciparum, one of the species of Plasmodium that causes malaria in humans, is transmitted by Anopheles mosquitoes that normally bite (and inject the deadly parasites) at night," CORDIS News reports (8/11).

For the study, researchers developed "a mathematical simulation model for P. falciparum transmission in Africa, which incorporated three major types of mosquito, parasite prevalence data in 34 areas of Africa with differing P. falciparum malaria transmission levels, and the effect of switching to artemisinin-combination therapy and increasing coverage of long-lasting insecticide treated bednets," according to a PLoS Medicine press release. The "authors explored the impact on transmission of continued roll-out of long-lasting insecticide treated bednets, additional rounds of indoor residual spraying, mass screening and treatment and a future vaccine in six representative settings with varying transmission intensity with the aim of reaching a realistic target of 80% coverage," according to the release (8/10).

The results of the model led the study authors to conclude: "In a low-transmission setting, 80% coverage with LLINs reduced the parasite prevalence to below 1% in all age groups. In two moderate-transmission settings, LLIN scale-up alone failed to reach this target but the addition of IRS [indoor residual spraying] and MSAT [mass screening and treatment] drove the parasite prevalence below 1%," according to the authors. "However, this combination of interventions did not control malaria in a moderate-transmission setting in which a mosquito species that bites and rests outside houses contributes to malaria transmission," according to the study (Griffin et al., 8/10).

The model highlighted the need for new methods to combat malaria "in high-transmission areas and those where mosquitoes mainly bite outdoors. Given the current set of tools, say the authors, it is unrealistic to expect that parasite prevalence could drop below 1% in some settings with high transmission," CORDIS News continues.

"There is renewed enthusiasm to rid the world of malaria, rather than just control the disease," SciDev.Net notes in an article that examines how the findings could help guide such efforts (Shetty, 8/12).

Although the authors cautioned, "This new mathematical model greatly simplifies the complex dynamics of malaria transmission and includes several assumptions about which there is considerable uncertainty." As such, "the findings of this study are not … firm predictions of the future of malaria control in specific settings … they suggest that it should be possible to make large reductions in malaria transmission and the associated disease burden in Africa over the next 25 years using currently available tools" (8/10).

"Our model can help planners evaluate the likely impact of combining interventions," Azra Ghani, an infectious disease epidemiologist at Imperial College and lead author of the study, said, according to SciDev.Net. "It can help them to prioritise where resources are limited." The article also includes quotes from Geoff Targett of London School of Hygiene and Tropical Medicine, who was not a study author (8/12).

This article was reprinted from khn.org with permission from the Henry J. Kaiser Family Foundation. Kaiser Health News, an editorially independent news service, is a program of the Kaiser Family Foundation, a nonpartisan health care policy research organization unaffiliated with Kaiser Permanente.