If Elimination is a Stable State, How Do We Get There?

The Keystone Symposium on The Science of Malaria Eradication entered its second day of activities with a focus on drug based strategies and health systems research in the elimination context. The evidence for use of single dose primaquine to clear P. falciparum infections, the new K-13 artemisinin resistance marker, and how clearing asymptomatic infections in children can improve cognition and reduce transmission all featured in the animated discussions.

Elisabeth A. Winzeler (University of California San Diego, USA) opened the morning session. She spoke about technologies that encompass the use of phenotypic screens coupled with genomics for drug discovery. The aim is to identify compounds that are active against all stages of the parasite (including hypnozoites) and discover targets for radical cure and transmission blocking.

Tim Wells (Medicines for Malaria Venture, Switzerland) challenged the audience to think about the drug pipeline in new ways. According to Tim, in the studies that evaluate the efficacy of the antimalarial drugs “it is equally important to measure when the parasite goes away and when the parasite comes back”. Finally, he highlighted the need to design novel ways of using today’s antimalarials as well as the development of future drugs.

Audience and speakers discussed the potential use of primaquine for clearing P. falciparum gametocytes and thereby reducing transmission with a single dose; something that has been already used and documented in several parts of the globe.  And Marcus Lacerda (Tropical Medicine Foundation, Brazil) reminded us that many knowledge gaps in drugs for P. vivax have still not been addressed, namely the ability of to kill hypnozoite without a partner drug; the different primaquine dosage regimens in different parts of the world; and G6PD deficiency management.

The audience later learned about exciting new results and the discovery of a novel molecular marker, the K-13-propeller, associated with resistance to artemisinin. Speakers pointed to potential uses in surveillance and elimination of artemisinin resistant parasites in the Greater Mekong subregion.

Speakers Marcel Tanner (Swiss Tropical and Public Health Institute) and David Smith (Johns Hopkins Bloomberg School of Public Health, USA) delivered very animated presentations relating to the critical role of the health system in driving down infections and keeping them out. ‘Surveillance’ was the key word: to inform interventions and adapt programmes to real needs. Research needs include understanding what the minimal essential data are for an elimination effort, and to understand where health system effectiveness is lost in a given socio-economic environment. The positive news from historical patterns studied with mathematical modelling is that once eliminated, malaria seems to stay eliminated. The strength of the health system being key to keeping malaria out.

To end the day, the focus shifted to school-based operational research in Mali, where drugs to clear parasites in children showed encouraging results. According to Sian Clarke (London School of Hygiene and Tropical Medicine, UK), data suggests that children perform better in schools after taking drugs that clear their malaria (even those with very low parasitaemia) and that such interventions can play a role in transmission reduction.

This all provided food for thought over lite bites and discussions continued at the stimulating poster session.

[This blog was written by MESA Secretariat, and posted simultaneously on MESA’s blog on Malaria World and ISGlobal’s blog.]