How much more malaria could be prevented?
Authors: Brian Greenwood
Journal: The Lancet Infectious Diseases (2016)

Measurement of the global burden of malaria is difficult, because many deaths from malaria occur outside the health-care system and other infections might be misdiagnosed as malaria unless a diagnostic test is done. However, there is general agreement that a substantial reduction in both deaths from malaria and cases has occurred during the past decade.1Murray CJ Oertblad KF Guinovart C et al.Global, regional, and national incidence and mortality for HIV, tuberculosis, and malaria during 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013.Lancet. 2014; 384: 1005-1070Summary Full Text Full Text PDF PubMed Scopus (694) Google Scholar, 2Gething PW Battle KE Bhatt S et al.Declining malaria in Africa: improving the measurement of progress.Malar J. 2014; 3: 39Crossref Scopus (35) Google Scholar WHO estimates that between 2000 and 2015, the annual incidence of malaria cases fell by 37% and that the malaria mortality rate fell by 60%.3WHOWorld Malaria Report 2015. World Health Organization, Geneva2015Google Scholar These reductions have been achieved largely through scale-up of insecticide-treated bednets and provision of prompt access to effective treatment. Can even better results be obtained from more of the same? WHO estimated that in 2015, about 68% of individuals at risk from malaria slept under an insecticide-treated bednet; this is probably a generous estimate, which might not account for intermittent use of nets, and additionally only few cases received treatment with artemisinin combination therapy. Thus, further scale-up of these interventions is needed. In the Lancet Infectious Diseases, Jamie Griffin and colleagues4Griffin JT Bhatt S Sinka ME et al.Potential for reduction of burden and local elimination of malaria by reducing Plasmodium falciparum malaria transmission: a mathematical modelling study.Lancet Infect Dis. 2016; (published online Jan 19.)http://dx.doi.org/10.1016/S1473-3099(15)00423-5Google Scholar used a well established model of malaria transmission5Griffin JT Hollingsworth TD Okell LC et al.Reducing Plasmodium falciparum transmission in Africa: a model based evaluation of intervention strategies.PloS Med. 2010; 7: e1000324Crossref PubMed Scopus (372) Google Scholar, 6Griffin JT Ferguson NM Ghani AC Estimates of the changing age-burden of Plasmodium falciparum malaria disease in sub-Saharan Africa.Nat Commun. 2014; 5: 3136Crossref PubMed Scopus (137) Google Scholar that accounts for increasing population size to predict what would happen if coverage of established interventions was increased to 80% or 90% with or without the addition of rectal artesunate. The model accounted for treatment of cases of severe malaria, and expansion of seasonal malaria chemoprevention to additional areas where it has not been recommended because suitable drugs are not available. Finally, they predicted what would happen if the status quo of coverage is maintained or allowed to fall back to the 2006 level. If the current level of coverage with insecticide-treated bednets and artemisinin combination therapy is sustained they predicted that the incidence of malaria would increase by 21% (95% CrI 18–23) and malaria mortality by 11% (7–16) between 2015 and 2030 due to population-level loss of immunity caused by successful reduction in the incidence of malaria during the previous years. With the scaling up of existing interventions to 90%, adoption of immediate treatment of severe malaria with rectal artesunate, and expansion of seasonal malaria chemoprevention they estimate that by 2030, malaria incidence would be reduced by 74% (95% CrI 70–77) and malaria mortality by 81% (76–87) preventing an estimated 3·37 billion cases (95% CrI 2·37 billion–4·33 billion) and 11·5 million deaths (4·6 million–16·0 million) over the 15-year period. However, an important issue not covered by Griffin and colleagues in this Article4Griffin JT Bhatt S Sinka ME et al.Potential for reduction of burden and local elimination of malaria by reducing Plasmodium falciparum malaria transmission: a mathematical modelling study.Lancet Infect Dis. 2016; (published online Jan 19.)http://dx.doi.org/10.1016/S1473-3099(15)00423-5Google Scholar is the cost of scale-up. As coverage improves, extending it will become more difficult and costly because access will be needed to communities living in remote areas or those who are suspicious of the formal health system and prefer to seek treatment elsewhere. Increasing coverage from 60% to 90% cannot be assumed to be half the cost of increasing coverage from 0% to 60%. Additionally, some communities are likely to be more receptive of one intervention than another and obtaining their views will be an important requisite to achieving very high coverage levels. Novel interventions for the control of malaria are being developed and some difficult decisions will be needed to determine how to balance investment in the deployment of these new interventions with efforts to further scale-up existing methods to very high levels of coverage. Use of models that include a range of costs for each intervention, old and new, could help guide the best approach in specific epidemiological situations, as has been shown in investigations of how best to deploy the malaria vaccine RTS,S/AS01.7Penny MA Verity R Bever CA et al.Public health impact and cost-effectiveness of the RTS,S/AS01 malaria vaccine: a systematic comparison of predictions from four mathematical models.Lancet. 2016; (published online Nov 5.)http://dx.doi.org/10.1016/S0140-6736(15)00725-4Google Scholar WHO has published a technical report that sets out the strategy for malaria control from 2016 to 2030.8WHOGlobal Technical Strategy for Malaria 2016–2030. World Health Organization, Geneva2015Google Scholar This report lists targets for reducing malaria cases and deaths from 2015 levels, by 40% in 2020, 75% in 2025, and 90% in 2030 with 10, 20, and 35 countries achieving malaria elimination by these dates. The modelling undertaken by Griffin and colleagues4Griffin JT Bhatt S Sinka ME et al.Potential for reduction of burden and local elimination of malaria by reducing Plasmodium falciparum malaria transmission: a mathematical modelling study.Lancet Infect Dis. 2016; (published online Jan 19.)http://dx.doi.org/10.1016/S1473-3099(15)00423-5Google Scholar suggests that these goals are not unrealistic, but this is the case only if they are not derailed by the spread of high-level resistance to drugs and insecticides, a supposition that cannot be assumed and that is not included in the model. Therefore, while strenuous efforts to scale-up existing interventions continue, research must continue for the development of new insecticides and antimalarial drugs, and on the development of vaccines and novel vector-control methods, which will almost certainly be needed before malaria is finally vanquished. I declare no competing interests. Potential for reduction of burden and local elimination of malaria by reducing Plasmodium falciparum malaria transmission: a mathematical modelling studyOur findings show that decreases in malaria transmission and burden can be accelerated over the next 15 years if the coverage of key interventions is increased. Full-Text PDF Open Access