About 40% of the world’s population is exposed to the risk of dengue and a large number of those people live in India, which has several virulent outbreaks of the disease especially in its monsoon months. Scientists have been tinkering with mosquito genes to find ways to control mosquito-borne disease like malaria and dengue and may have now created a genetically modified mosquito that can resist infection by the dengue virus and therefore cease to spread it.

Dengue is spread through the Aedes aegyptii mosquitos. Mosquitos that feed on the blood of an infected person pass the disease on when they subsequently bite a healthy person. Researchers from the Johns Hopkins Bloomberg School of Public Health have shown that the Aedes aegyptii’s natural ability to fight the dengue virus can be boosted to reject infection in the mosquito in the first place.

In research published in PLOS Neglected Tropical Diseases they describe manipulating a component of the Aedes aegyptii immune system called the JAK-STAT pathway, that regulates production of antiviral factors. The genetic modification resulted in fewer mosquitoes becoming infected. Most of the mosquitos that did get infected had very low levels of dengue virus in their salivary glands. However, the genetic modification did not make the mosquitos resistant to two other diseases that their also are capbale of carrying – Zika and chikungunya.

The team also found that the dengue-resistant mosquitoes live as long as the wild mosquitoes but produce fewer eggs, making it likely that the same mechanism that triggers the immune system plays a role in egg production.

Genetic modification of mosquitos for disease elimination is based on the theorro of “gene drives” that involve replacing the natural population of mosquitos with GM mosquitos that cannot spread the disease. A laboratory at Jalna in Maharashtra has been performing similar genetic experiments for dengue control. However, some scientists and ethicists hold the view that there can be unintended and unforseeable consequences of such large scale manipulations, some that maybe dangerous or even devastating.