The ecology and evolution of Plasmodium falciparum malaria among rural communities in Madagascar

Abstract

Parasites in the genus Plasmodium annually cause hundreds of millions of cases of malaria worldwide, and more than a million cases in Madagascar alone. Alarmingly, multiple lines of evidence suggest that, counter to general trends elsewhere, the burden of malaria has increased in regions of Madagascar in recent years. Understanding the drivers and distribution of malaria among communities in Madagascar is hampered by limited health surveillance capacity and extremely high inter-regional ecological variation. This motivates the development of new approaches to studying and controlling malaria in Madagascar, especially approaches that are not reliant on the existing limited health monitoring infrastructure and that can be deployed in remote communities. One such approach is the use of population genetic data to infer trends in the parasite population from a sample of infections. To implement this approach, we completed new, multi-method field studies of rural communities in Madagascar (Chapter 2), characterized spatial variation in the prevalence of malaria infection observed at those study sites (Chapter 3), validated a panel of single nucleotide polymorphisms (SNPs) (Chapter 4), and then compared patterns in parasite genetic diversity at that SNP panel across eco-regions of Madagascar (Chapter 5). In remote communities situated within the tropical rainforest environments of northeastern Madagascar and the semi-arid, spiny forests of southwestern Madagascar, we find evidence of: (i) high, but spatially variable malaria prevalence, (ii) high levels of within host parasite genetic diversity, and (iii) high levels of genotypic diversity in P. falciparum populations. Together, these data are consistent with the presence of communities with concerningly high burdens of malaria in rural Madagascar and have implications for future control efforts.