History of Malaria - 21st Century

21st Century

Drug resistance poses a growing problem in the treatment of malaria in the 21st century, since resistance is now common against all classes of antimalarial drugs, with the exception of the artemisinins. This situation has resulted in the treatment of resistant strains becoming increasingly dependent on this class of drugs. However, the artemisinins are expensive, which limits their use in the developing world. Worrisome evidence is now emerging of malaria on the Cambodia-Thailand border that are resistant to combination therapies that include artemisinins, which raises the possibility that strains of malaria may have evolved that are untreatable with currently available drugs. Exposure of the parasite population to artemisinin monotherapies in subtherapeutic doses for over 30 years, and the availability of substandard artemisinins, have probably been the main driving force in the selection of the resistant phenotype in the region.

The application of genomics to malaria research is now of central importance. With the sequencing of the three genomes of the malaria parasite P.falciparum, one of its vector Anopheles gambiae, and the human genome, the genetics of all three organisms in the malaria lifecycle can now be studied. This breakthrough is expected to produce advances in the understanding of the interactions between the parasite and its human host—such as between virulence factors and the human immune system—as well as allowing the identification of the factors that restrict one species of parasite to one or a few species of mosquitoes. It is likely that these will eventually lead to new therapeutic approaches. Another new application of genetic technology is the ability to produce genetically modified mosquitoes that are unable to transmit malaria, allowing biological control of malaria transmission.

The World Health Organization (WHO) recommends Indoor residual spraying as one of three primary means of malaria control, the others being use of insecticide-treated mosquito nets (ITNs) and prompt treatment of confirmed cases with artemisinin-based combination therapies (ACTs). The use of ITNs to prevent malaria has been recommended by Giving What We Can as one of the most cost-effective means of combating the disease. For example, interventions such as Against Malaria Foundation are able to prevent malaria-related deaths at $1,600 per person, with one malaria net costing $5. In 2000, only 1.7 million (1.8%) African children living in stable malaria-endemic conditions were protected by an ITN. That number increased to 20.3 million (18.5%) African children using ITNs by 2007, leaving 89.6 million children unprotected. An increased percentage of African households (31%) are estimated to own at least one ITN in 2008 (WHO World Malaria Report 2009). Most nets are impregnated with pyrethroids, a class of insecticides with particularly low toxicity. Dow AgroSciences developed a microencapsulated formulation of the organophosphate chlorpyrifos methyl as a cost-effective, long-lasting alternative to DDT. As an Indoor residual spraying against pyrethroid resistant mosquitoes chlorpyrifos methyl outperformed DDT and lambdacyhalothrin. Organizations such as the Clinton Foundation continue to supply anti-malarial drugs to Africa and other affected areas; according to director Inder Singh, in 2011 more than 12 million individuals will be supplied with subsidized anti-malarial drugs. Other organizations, such as Malaria No More continue distribution of more broad-based prophylaxis.