In the first post of this series, I presented a brief overview of the paper called “Transgenic Aedes aegypti mosquitoes transfer genes into a natural population”, which focuses on Oxitec’s recent field trial with (non-gene-drive) transgenic mosquitoes in Brazil. As I mentioned, the paper speculates on the potential impact of gene flow – not of the transgene, but of the rest of the genetic makeup of the released mosquitoes. In this second of two posts, I will focus on the following question “what is the impact of introgressing background genetic information from a release strain into a local population”?

Almost all genetic control systems will do this, unless the released mosquitoes are truly, absolutely, completely incapable of forming fertile hybrids with the local target population. Note that this has little to do with transgenes, and applies equally to classical radiation-based SIT, Wolbachia-based gene drives, etc.

The use of gene drives – or any genetic pest management method – involves releasing gene drive-carrying organisms, e.g. mosquitoes, to mate with wild mosquitoes in the target area. Their offspring carry the gene drive which then goes off to do whatever it was designed to do. But what about all the other (non-gene-drive) genes in the released mosquitoes? What happens to them? They also enter the population’s gene pool, though unlike the gene drive they have no special mechanism to allow them to spread. Does that matter? Contrary to some recent speculation, probably not, at least in most cases.

Genetic control of mosquitoes involves introducing some sort of modified heritable trait into a wild mosquito population. That involves rearing modified mosquitoes in the lab and releasing them to mate with the target wild mosquito population. That mating delivers the modified genetic trait into the wild population and, if that’s a gene drive and the conditions are right, that gene drive will start to do its thing in that population, for example start to increase in frequency.

Researchers from Stanford University and Florida University found strong evidence that deforestation increases malaria transmission, while high malaria incidence simultaneously reduces forest clearing. To reach that conclusion, they analysed a geospatial dataset encompassing 795 municipalities across the Amazon basin between 2003 and 2015.

The New Partnership for Africa's Development (NEPAD) published the results of their workshops on the perception of gene drive technology for malaria control in Africa, carried out from 2016 to 2018. These events brought together scientists, ethicists, health professionals, government regulators in the fields of environmental health and biosafety and government policymakers to deliberate on malaria reduction goals and pathways to the use of gene drive to that end.

Sub-Saharan African leaders are working together to reignite the pace of progress in the global malaria fight following the High burden to high impact (HBHI) approach – a country-led response to combat the vector-borne disease catalyzed by WHO and the RBM Partnership.

Countries are currently developing national malaria databases that draw on health systems, surveys, research and climate data to better understand the disease’s patterns and the effects of potential interventions. The database aims to improve the quality of information available and, consequently, help identify the most effective policies and intervention tools to control and reduce the burden of the disease.