CSU 114/2010: KEVIN MARSH ON MALARIA

Tuesday, 9th of November 2010

CSU 114/2010: KEVIN MARSH ON MALARIA

If you have an hour to spend on malaria, why not spend it listening to Kevin Marsh, of KEMRI/Kilifi, on the BBC World Service at http://www.bbc.co.uk/worldservice/programmes/2009/12/091201_exchanges_frontier_list.shtml

Among his interesting findings: coastal Kenya, where he works, started to see malaria mortality declines before the introduction of ACT and LLINs.

If you don’t have an hour, read his piece on research priorities for malaria elimination, below. Full text, with references, is at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)61499-7/fulltext?_eventId=login

With the increase in annual global malaria funding from $200 million to >$2 billion, one should not think small.

Readers with interests in malaria research should also consult the malERA homepage at http://malera.tropika.net/

Good reading.

Ioutline goes here

The Lancet, Early Online Publication, 29 October 2010

doi:10.1016/S0140-6736(10)61499-7 Cite or Link Using DOI

Research priorities for malaria elimination

Original Text

Kevin Marsh a

The Lancet's four-paper Series examines the need for, and prospects of, malaria elimination. The papers make sobering reading. Elimination will be hard work, it will take a long time, and it will be expensive. Moreover, elimination requires that we first control malaria to the point where it is no longer a public health problem, and this is by far the most important, immediate target for increased and sustained international investment.1 Nonetheless, elimination (and eventually eradication) is still important as a long-term goal, both for countries that are currently or will shortly be in a position to consider it, and worldwide. One of the most positive effects of the renewed focus has been to galvanise the research community through the Malaria Eradication Research Agenda (malERA),2 a process that has developed a remarkable consensus for reformulating the entire malaria research agenda. malERA will soon launch its detailed conclusions of a long-term agenda for everything from basic science to operational research, but in light of this Series, what research priorities are specific to elimination right now?

The most obvious and immediate priority is for improved data to guide policy makers in moving from control to elimination. Two papers in the Series take different but complementary approaches and both are extremely cautious in their conclusions and emphasise the paucity (or often absence) of essential data. Development of robust, predictive models of a technical and operational capacity for elimination needs comprehensive and detailed data for the distribution of all malaria species that are able to infect people, for the worldwide distribution of anopheline vectors, and, at a country and subnational level, for health systems and financing data.3 Although robust assessments of costs and financial feasibility of elimination are crucial, Oliver Sabot and colleagues 4 point to the massive gap in empirical evidence, particularly regarding the quantification of marginal costs and long-term financial benefits and threshold benefits that are hard to formulate.

For epidemiological research there are three major priorities. First, there should be a renewal of support for vector research. This priority goes well beyond epidemiology; malaria is a vector-borne disease, but support for many areas of vector biology has waned—a dangerously short-sighted approach. Second, as malaria transmission declines, understanding heterogeneity in malaria transmission becomes crucial, and innovative approaches are needed in the field and in modelling.5 Third, our understanding of Plasmodium vivax epidemiology is very limited and yet for most of the 32 so-called malaria-eliminating countries, P vivax is the main, or a major, part of the problem.

As low-endemic control is approached, operational challenges arise, particularly with regard to how the malaria problem should be quantified and what should be done when infected patients are found. The traditional approach of community surveys becomes progressively more difficult and less informative as prevalence falls to low levels. One could easily say “move to active case detection”, but that begs the question of how to move and how well detection works, especially in environments with poor health systems. When parasitological detection (rather than disease diagnosis) is the aim, sensitivity becomes paramount. PCR and other new approaches are attractive, but how does one move these techniques from research centres to health systems? Mass-treatment approaches to clearing asymptomatic parasite carriage require drugs with better safety profiles than treatment drugs. Again, P vivax presents special challenges, which Kevin Baird considers in his Comment.6

A key issue that has not received enough attention is how to define, monitor, and respond to resurgence risks in areas where low-endemic control has been achieved, but where potential for transmission remains high. In such a context, an effective vaccine could have a new role—beyond contributing to initial control or supplying the final push to elimination—by providing immunity to at-risk populations who no longer acquire natural immunity.

Finally, I have two crucial points. First, the welcome, renewed emphasis on taking action should not reduce basic scientific malaria research. All the easy stuff has been done and it is extremely unlikely that the endgame will be closed without an increased understanding of parasite biology. Second, development of research leadership in endemic countries is not simply a politically correct mantra, but an essential requirement for long-term success. This development takes time and much more investment than there is now. While it might be tempting to use external quick fixes, such an approach would be fundamentally misguided.

I declare that I have no conflicts of interest.

References

1 Snow RW, Marsh K. Malaria in Africa: progress and prospects in the decade since the Abuja Declaration. Lancet 2010; 376: 137-139. Full Text | PDF(68KB) | CrossRef | PubMed

2 The Malaria Eradication Research Agenda (malERA). http://malera.tropika.net. (accessed Sept 11, 2010).

3 Tatem AJ, Smith DL, Gething PW, Kabaria CW, Snow RW, Hay SI. Ranking of elimination feasibility between malaria-endemic countries. Lancet 201010.1016/S0140-6736(10)61301-3. published online Oct 29. PubMed

4 Sabot O, Cohen JM, Hsiang MS, et al. Costs and financial feasibility of malaria elimination. Lancet 201010.1016/S0140-6736(10)61355-4. published online Oct 29. PubMed

5 Bejon P, Williams TN, Liljander A, et al. Stable and unstable malaria hotspots in longitudinal cohort studies in Kenya. PLoS Med 2010; 7: e1000304. CrossRef | PubMed