The Zika virus is spreading through the Americas at an alarming rate. The World Health Organisation (WHO) have created an emergency committee to address the outbreak and advise pregnant women not to visit affected areas. The virus has been linked with an increase in babies born with microcephaly: reduced size of the head and brain. We recently wrote a guide to everything you need to know about the Zika virus. Something else we’ve discussed is the incredible gene-editing tool CRISPR-Cas9. Scientists are now debating whether or not we should use the technology in the fight against the mosquitoes carrying the Zika virus.
Modifying mosquitoes is not a new idea and is already happening. Sadly these traditional transgenic techniques are expensive, time-consuming, and difficult. The entire population would need to be replaced meaning we would have to constantly release transgenic mosquitoes into the wild over large areas and in the long-term. The science behind the approach is solid but the efforts are impractical.
The CRISPR technique might provide a better solution. Scientists have identified a gene called Nix, which is involved in the mosquitoes’ sex-determination. The CRISPR system allows biologists to edit recise regions of the genome easily, cheaply, and quickly. Two biologists, Adelman and Tu, have already demonstrated that CRISPR can edit this gene in female embryos causing them to develop male genitalia. They showed this is Aedes aegypti, which is the very species currently spreading the Zika virus through the Americas.
In theory this should work. Scientists can edit the genome in such a way that the Nix gene is non-functional and this change can be spread through the population in a method known as a gene drive. In practice, it hasn’t been done before in the wild and there may be unforeseen consequences. The gene drive technique that would be employed is extremely powerful and can permanently alter entire populations, meaning the scientists would have a great deal of responsibility.
Once successfully tested in a willing region, we will probably see widespread use of gene-editing technology to reduce mosquito populations by removing females. This could be a solution not just for slowing the spread of Zika, but reducing the numbers of mosquitoes that carry dengue, yellow fever, and even malaria. Now the scientists just need to find a place where a government and the public are willing to have gene-edited mosquitoes released, which could be easier said than done.
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