Researchers at the University of California San Diego have capitalized on advances in CRISPR-based genetic engineering and created a new system to hold back mosquito populations that infect millions with debilitating diseases each year.
The new precision-controlled sterile insect technology (pgSIT) alters genes associated with male fertility – it produces sterile offspring – and female flight in Aedes aegypti, the species of mosquito responsible for spreading widespread diseases such as dengue, chikungunya and zika is.
pgSIT is a new scalable genetic control system that uses a CRISPR-based approach to develop usable mosquitoes that can suppress populations. Men do not transmit disease, so the idea is that if you release more and more sterile men, you can suppress the population without relying on harmful chemicals and insecticides. “
Omar Akbari, professor of life sciences at UC San Diego
Details about the new pgSIT will be described in the journal Nature Communications on September 10, 2021.
pgSIT is different from gene drive systems, which could suppress disease vectors by indefinitely passing desired genetic changes from one generation to the next. Instead, pgSIT uses CRISPR to sterilize male mosquitoes and render female mosquitoes, which spread disease, incapable of flight. The system is self-limiting and is not expected to persist or spread in the environment, two important safety features that should allow this technology to be adopted.
Akbari says the proposed pgSIT system could be implemented by laying eggs from sterile males and flightless females in destinations where mosquito-borne diseases spread.
“Supported by mathematical models, we empirically show that released pgSIT males can compete and suppress and even eliminate mosquito populations,” the researchers write in the publication by Nature Communications. “This platform technology could be deployed in the field and adapted to many vectors to control wild populations to contain disease in a safe, limited and reversible manner.”
Although the tools of molecular genetic engineering are new, farmers have been sterilizing male insects to protect their crops since at least the 1930s. Breeders in the United States began using radiation in the 1950s to use radiation to pest species like the New World Screwworm fly, which is known for destroying livestock. Similar radiation-based methods continue today along with the use of insecticides. pgSIT is designed to be a much more precise and scalable technology as it uses CRISPR – no radiation or chemicals – to alter key genes in mosquitoes. The system is based on a method announced by UC San Diego in 2019 by Akbari and his colleagues for the fruit fly Drosophila.
As intended, Akbari says pgSIT eggs can be shipped to a mosquito-prone location or developed at a local facility that could produce the eggs for use nearby. Once the pgSIT eggs are released in the wild, typically at a peak rate of 100-200 pgSIT eggs per adult Aedes aegypti, sterile pgSIT males hatch and eventually mate with females, displacing the wild population as needed.
Beyond Aedes aegypti, researchers believe pgSIT technology could target other species that spread disease.
“… This study suggests that pgSIT could be an efficient technology for mosquito population control and the first example of one that is suitable for release in the real world,” say the researchers. “Going forward, pgSIT could provide an efficient, safe, scalable and environmentally friendly next-generation alternative technology for the control of the wild mosquito population, leading to comprehensive prevention of disease transmission to humans.”
University of California – San Diego
Li, M., et al. (2021) Suppression of mosquito populations with precision-guided sterile males. Nature communication. doi.org/10.1038/s41467-021-25421-w.