Progress in the fight against malaria in sub-Saharan Africa has stalled. The statistics surrounding the disease are depressing. The mosquito is by far the leading agent of death worldwide causing an estimated 1,000,000 deaths annually (admittedly, these aren’t only from malaria, but also dengue fever, yellow fever, and the Zika virus). Humans are a distant second with less than half of the mosquito’s total (about 431,000 from homicides and armed conflicts). Sub-Saharan Africa accounts for roughly 95% of the malaria deaths with children between the ages of 0-5 years being the most vulnerable, accounting for about 75% of the sub-Saharan deaths. This group bears a disproportionate share of the deaths because they are yet to develop natural immunity against the disease.
In Nigeria, an estimated 68 million cases of malaria occur annually. That is about 27% of the global case burden, making malaria in Nigeria a year-round public health threat, especially in northern regions.
Decades of effort have been made in a bid to eradicate the disease from the continent, and encouragingly notable progress was made between 2000 and 2015 in this regard. This progress has now ground to a halt, the result of shrinking budgets and the weakening of the efficacy of existing measures. Interventions that were once highly effective are losing their edge as mosquitoes develop resistance to the insecticides used in treated bed nets and for indoor spraying, as well as to anti-malarial drugs.
Climate change is compounding the challenge: rising temperatures are expanding mosquito habitats, whilst floods and population displacement are exposing communities with little natural immunity to malaria risk and simultaneously disrupting access to the health services those communities depend upon.
To get the eradication programme back on track, some stakeholders like the director of GeneConvene Global Collaborative (an international initiative created to advance best practices and support informed decision-making regarding the development of genetic biocontrol technologies), Dr. Michael Santos, believes that the use of Gene Drive Technology, could be what would tip the scales in the battle against malaria.
Gene drive technology is a genetic engineering method that forces a chosen trait to spread rapidly through a population, and in malaria control it is being developed to reduce or alter mosquito populations so they can no longer transmit the disease. The most promising approaches target anopheles gambiae (the main malaria disease-carrying vector) mosquitoes by reducing female fertility (thus reducing their ability to reproduce) or skewing sex ratios (i.e. engineer mosquitoes to produce mostly male offspring, reducing the number of biting females that transmit malaria), which could drastically cut malaria transmission in Africa.
Ordinarily, sex selection genes have a 50-50 chance of being passed onto the next generation. Gene drive technology ensures that modified genes are inherited about roughly 99% of the time, thus ensuring rapid spread through a population. The idea is that over generations, the mosquito populations will shrink, cutting malaria transmission. Alternatively, mosquitoes could be engineered to resist malaria parasites like plasmodium falciparum, thus breaking the transmission cycle.
Once released, modified mosquitoes spread the trait without repeated interventions, thus reducing reliance on preventive measures that require disciplined human behavior, like the use of insecticides and bed nets. Gene drive technology thus has the potential to cover large regions where malaria is endemic, like Africa.
Gene drive technology, as marvelous as it sounds, is not without risks and challenges. Large scale reduction of mosquito populations may cause undesirable imbalances in the ecosystem that cannot be predicted beforehand, therefore the release of such modified mosquitoes would need to be subject to strict biocontrol procedures. Effective use of such procedures require international cooperation…always a complex undertaking.
Gene drive technology is still some way from being live deployment ready. Most work in the field is still restricted to laboratory research and trials. There are some programmes ongoing that are helping to prepare the way for public acceptance of gene drive technology through community engagement activities like the Target Malaria programme currently underway in Burkina Faso, Mali, and Uganda, but no date has been set for open-field trials of gene drive technology. If or when we do cross that bridge, it is sure to push the battle against malaria to an exciting frontier.
