New technology designed to genetically control disease-spreading mosquitoes

Stephanie Gamez, coauthor of the study, illustrates flightless females with sterile males. This is the feature of the precision-guided sterilize insect technique (pgSIT), which is used to control Aedes Aegypti mosquitoes. Credit: Stephanie Gamez, UC San Diego
Researchers at the University of California San Diego created a new system to control mosquito populations that carry debilitating diseases.

The precision-guided sterile insect technique (pgSIT) alters genes that are linked to male fertilitycreating sterile offspringand female flight in Aedes aegypti. This is the mosquito species responsible of spreading many diseases such as Zika and chikungunya.

Omar Akbari, UC San Diego Biological Sciences Professor, said that "pgSIT" is a new scalable genetic system that employs a CRISPR-based method to engineer mosquitoes that can suppress population. "Males don’t transmit diseases, so it is possible to suppress the population by releasing more sterile males without using harmful chemicals or insecticides.

Details about the new pgSIT can be found in Nature Communications, September 10, 2021.

pgSIT is not like "gene drive" systems, which could suppress disease vectors by passing on desired genetic alterations indefinitely to each generation. Instead, pgSIT employs CRISPR to sterilize male and female mosquitoes. This prevents them from spreading disease. This technology is safe and self-limiting. It is not expected to spread or persist in the environment.

Akbari suggests that the pgSIT system be implemented by placing eggs of sterile males in areas where mosquito-borne diseases are occurring.

The Nature Communications paper notes that "Supported with mathematical models, we empirically prove that released pgSIT men can compete, suppress, and even eliminate mosquito population," according to the researchers. This platform technology could be applied in the field and adaptable to other vectors for control of wild populations and curtail disease in an efficient, safe, and reversible way.

Ming Li, UC San Diego Postdoctoral Fellow, is the first author of a Nature Communications paper describing a CRISPR based precision-guided sterile in insect technique in Aedes aegypti moths. He shows sorting pgSIT larvae. Credit: Akbari Lab, UC San Diego

Although molecular genetic engineering tools may be new, farmers have been sterilizing male insect larvae to protect their crops since at most the 1930s. In the 1950s, American growers used radiation to kill pest species like the New World Screwworm Fly. Today, similar radiation-based methods are used alongside the use of insecticides. Because it does not use radiation or chemicals to alter key mosquito genes, pgSIT can be more precise and scaleable. This system was developed from a method first announced in 2019 at UC San Diego by Akbari and his colleagues working in Drosophila, the fruit fly.

Akbari states that pgSIT eggs could be shipped to areas where mosquito-borne diseases are likely or can be developed on-site at a facility that could produce eggs for local deployment. The pgSIT egg will be released into the wild at a peak rate between 100-200 pgSIT per Aedes Aegypti adult. Once they are released, the sterile males of pgSIT will eventually mate with the females to reduce the wild population.

Researchers believe that the pgSIT technology can be used to spread disease beyond Aedes Aegypti.

The researchers state that pgSIT could be an effective technology for controlling mosquito populations and may be the first to be released in the real world. "PgSIT could be a safe, efficient, scalable and environmentally friendly next-generation technology that can control wild mosquito populations. This will allow for widespread prevention of disease transmission.

More information: Nature Communications, Suppressing the mosquito population with precision guided male steriles (2021). Information from Nature Communications: Suppressing mosquito population with precision-guided sterile males (2021). DOI: 10.1038/s41467-021-25421-w