Malaria Elimination: What´s Evolutionary Biology Got To Do With It

Malaria Elimination: What´s Evolutionary Biology Got To Do With It

21.6.2017
image alt

Over the past decade we have witnessed great success in reducing malaria morbidity and mortality worldwide. Several countries are even reaching, or working hard towards the elimination of malaria. Much of the successes can be attributed to insecticide- and antimalarial-based interventions: Long-Lasting Insecticidal Nets (LLINs), indoor residual spraying (IRS) and artemisinin combination therapy (ACT).  All three of these are amazing and effective tools. The threat however is whether they will lose their effectiveness as a result of resistance evolution.

Resistance has emerged against nearly every antimalarial drug and insecticide we have available

Resistance has emerged against nearly every antimalarial drug and insecticide we have available. Of the four classes of insecticides available for vector control, resistance has been reported in some areas to three or even all four of these. Likewise, antimalarials have faced resistance evolution since the first widespread use of chloroquine, which had to be replaced in by the drug sulphadoxine-pyrimethamine in many places, which in its turn had to be replaced just several years later by the current ACTs.

Resistance to ACTs is now spreading in South-East Asia with no new class of antimalarial ready to replace it. With such evolution in action, malaria elimination goals may be threatened by failing interventions.

Resistance is an evolutionary problem at the core. It follows the principles of Darwinian selection

Resistance is an evolutionary problem at the core. It follows the principles of Darwinian selection: Those individuals, be it parasites or mosquitoes, most adapted to the current – toxic – environment are the ones that survive and produce offspring, it is thus the offspring of these better adapted individuals that are represented at a higher frequency in the next generation. The spread of such mutant individuals depends on an intricate balance between their level of resistance, their fitness cost and the likelihood that any individual in the population encounters the chemical.

Seeing the failure of malaria interventions as an evolutionary process, resistance management strategies can be designed to minimize the fitness of mutants, hence slowing down the spread of resistance, using these three factors mentioned above. Unfortunately, evolutionary biologists by enlarge ignore the problem of resistance evolution (which I have discussed in the past). However, examples of evolutionary biology inspired interventions can be found in these three articles: How to Make Evolution-Proof Insecticides for Malaria ControlUsing evolution to generate sustainable malaria control with spatial repellents; and The evolution of drug resistance and the curious orthodoxy of aggressive chemotherapy.

Evolution is a problem for global health in general. This goes beyond drug resistance and insecticide resistance such as mentioned here, but also affects our food production as antibiotic, antifungal, herbicide and pesticide resistance in agriculture is a widespread problem. For the case of malaria, current searches for novel tools are having great progress, but also vaccines, mosquito trapping devices or genetically modified mosquitoes, just to name a few, are not evolution-proof either.

A greater incorporation of evolutionary biology at both the intervention development as well as policy level is urgently needed

A greater incorporation of evolutionary biology at both the intervention development as well as policy level is urgently needed, to allow us to develop improved resistance management strategies with the ultimate goal to achieve a malaria-free world.