According to studies, mosquitoes are one of the deadliest creatures on Earth, albeit indirectly. Thanks to the fact that they carry several types of viruses, bacteria, parasites and other disease sources, which they transmit through their bites, mozzies kill around a million of the 700 million people they infect annually.
For this reason, people are looking for innovations like Deet free repellent in Australia to keep them safe, as international travel, globalization as well as climate change has led to mozzie infections being a global problem. Pathogens like the West Nile virus (WNV) have caused outbreaks even in countries like the US, on top of new pathogens being discovered.
Currently, control efforts are limited to insecticide sprays, though there are some issues, even with Deet free repellent in Australia and across the world. To that end, scientists have turned to genetically modifying mosquitoes to control disease outbreaks. It’s not a new idea, having been suggested as far back as the 40s.
As it stands, there are two methods to utilizing GM mozzies; population replacement and population suppression. The former is replacing pathogen transmitting mosquitoes with ones unable to do so, taking advantage of ‘gene driving’, which uses a quirk on inheritance to spread a genetic trait to more than half of a specimen’s offspring, to spread the anti-pathogen genes. The latter, meanwhile, outright curbs the ability of mosquitoes to reproduce.
The concept of a gene drive is not restricted to genes, as all organisms posses what’s called a ‘hologenome’, which represents the genomes of all of their associated microbes. The Wolbachia symbiotic bacteria, known for infecting about 70% of all known insect species, is marked as the genetic trait that suppresses either the ability of insects to reproduce or spread pathogens, and is programmed to hijack the insect’s reproductive methods to spread itself through the species.
Within the last eight years, scientists have worked with Wolbachia, taking the strain in fruit flies and passing them, as well as at least 1,500 prerequisite genes, into mosquitoes that transmit dengue, who were then released into a dozen countries to curb the spread of the disease. Preliminary results from the releases in the AU have shown promise, but the countries with higher disease density like South America and Asia still need further study.
For population suppression, scientists have been sterilizing mosquitoes by modifying males of the species to carry a gene that is lethal to the females, leaving the males, who do not bite or transmit the disease. These males are then released to nature, where they mate with the wild female population, which result in male offspring with the genetic quirk, and dead females, which cut down on the species’ reproductive abilities.
There have been some opposition to these methods, though sterile mosquitoes are generally agreed upon by the scientific community to be the safest disease control method, not just for the species, but also for the environment, safer than broad-spectrum insecticide sprays if nothing else.
In an increasingly globalized world, pathogens are likely to spread across the world, and with insect resistance to insecticide growing, scientists are looking for ways to curb the damage done by mosquito-borne diseases, without risking the environment.