Malaria still kills one child every two minutes and it is estimated to cost the African economy more than US$12 billion every year (Target Malaria 2016). Current control methods such as insecticide-treated bed nets, indoor spraying of insecticides, and artemisinin-based drug treatments have saved millions of lives. However, insufficient resources, emerging insecticide resistance among mosquitoes, and challenging distribution conditions limit their ability to end malaria alone.
Scientists are studying complementary tools to fight this vector-borne disease. These include genetically modified mosquitoes, a technology still under development. Before releasing any modified mosquitoes, it is necessary to understand their potential impact on the environment, the conditions that can affect their spread and the gene drive mechanism.
In a study published by BMC Biology, Ace R. North, Austin Burt and H. Charles J. Godfray – part of the Target Malaria research team – shed light on these issues. They use mathematical models to evaluate the potential of genetically modified mosquitoes to suppress vector populations in a 106 km2 area of West Africa. This includes all of Burkina Faso, one of the countries most affected by malaria.
The study focuses on two species of malaria vectors - Anopheles gambiae and Anopheles coluzzii - and considers a type of gene drive called a “driving-Y chromosome”. Modified mosquitoes would produce mainly male offspring, which would also carry this modification. Over time, the number of female mosquitoes would decline, as well as the overall number of mosquitoes.
Authors suggest the technology could make a major contribution to malaria reduction: “repeated introductions of modified mosquitoes over a few years into a small fraction of human settlements may be sufficient to substantially reduce the overall number of mosquitoes across the entire geographic area”. Suppression, however, is not geographically uniform and seasonality is especially relevant for this variation. Regions with mild dry seasons are more likely to achieve the elimination of mosquito populations than regions with strong seasonality, where suppression is more common.