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Can we genetically control the world’s deadliest animal?

Researchers have developed a technology, which they called precision-guided sterile insect technique, that is able to suppress and eliminate harmful mosquito populations.

Mosquitoes are the world’s deadliest animal. They kill more humans than any other animal on earth. At least 725,000 individuals die per year from mosquito-borne diseases. Aedes aegypti, otherwise known as the yellow fever mosquito, is responsible for spreading a wide range of diseases including dengue fever, chikungunya and Zika virus. The species infects hundreds of millions of people annually and their success rate has largely been due to globalisation because they thrive in populated areas that lack reliable water supplies, waste management and sanitation. 

The predominant strategy that is used to control these diseases is the use of insecticides. However, in recent years mosquitoes have begun to evolve and show resistance to these control efforts. Therefore, there is an urgent demand for novel technologies to control mosquitoes that are effective, sustainable and safe.

Mosquitoes: Sterile males and flightless females

Since before the 1930’s, farmers have been sterilising male insects using radiation-based methods to protect their crops. Recently, scientists at the University of California, San Diego, developed a molecular genetic control system in Aedes aegypti, which uses a simple CRISPR-based approach to generate flightless females and sterile males.

The technology, called precision-guided sterile insect technique (pgSIT), disrupts the genes essential for male fertility and female flight. Flight is vital as needed for mating, blood feeding, reproduction and predator avoidance – basically survival. The researchers demonstrated that released pgSIT males could compete, supress and eliminate harmful mosquito populations, and supported their findings within mathematical models.

The system was designed to control populations of mosquitoes, in turn reducing the millions of people infected with diseases each year. Omar Akbari, Science Professor at the University of California, San Diego, explained:

“pgSIT is a new scalable genetic control system that uses a CRISPR-based approach to engineer deployable mosquitoes that can suppress populations. Males don’t transmit diseases so the idea is that as you release more and more sterile males, you can suppress the population without relying on harmful chemicals and insecticides.”

CRIPSR controlling mosquito populations

Overall, this study shows that pgSIT could be an effective technology for mosquito population control and may soon be suited for real-world release. The envisioned system could be implemented by deploying eggs of genetically engineered sterile males and flightless females at target locations where the spread of mosquito-borne diseases is highly. These eggs could either be shipped to the area or developed at an on-site facility. Once released, the sterile males would then emerge and mate with females, subsequently driving down the wild disease-spreading population of mosquitoes.

The system is self-limiting, meaning that it does not persist in the environment. This is an important feature of using CRIPSR technology to alter mosquito genes, making it a more scalable and precise method than radiation or chemicals. It is hoped that pgSITs will soon be used in the field and adapted to many other vectors to control wild disease-spreading populations in a safe and confinable manner. Nevertheless, more research is needed on CRISPR-based methods that rapidly spread target genes through a population before safe implementation can take place.

Image credit: Genetic Engineering and Biotechnology News

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