🦟 Google wants to release 64 million mosquitoes infected with a bacterium

Google recently filed a permit application with the U.S. Environmental Protection Agency. Its goal? To release 64 million mosquitoes in California and Florida. This initiative may seem strange, but it relies on a particularly ingenious biological trick.

In reality, these mosquitoes are not ordinary: they are males of the species Culex quinquefasciatus, infected with a bacterium called Wolbachia pipientis. This bacterium is harmless to humans and to the male mosquitoes themselves. However, when these infected males mate with uninfected females, the eggs produced cannot hatch. Result: the mosquito population gradually decreases.


Moreover, this technique, called cytoplasmic incompatibility, has already proven effective against other mosquito species, notably Aedes aegypti, which transmits dengue and Zika. In Singapore, trials showed a 90% reduction in the population of disease-carrying mosquitoes, and a 70% decrease in the risk of residents contracting dengue.

Additionally, scientists praise this approach because it is far more targeted than traditional insecticides. The latter often kill other beneficial insects, such as bees, and mosquitoes develop resistance. In contrast, the Wolbachia bacterium is natural and specific to certain insect species. It introduces no toxins into the environment.

As for ecological concerns, they are low. Predators that feed on mosquitoes are generally generalists and do not depend on a single species. Furthermore, the local disappearance of Culex quinquefasciatus could give way to other mosquitoes, but the public health benefits are considered far greater than the potential risks.

Indeed, this mosquito is the main vector of West Nile virus in the United States, a disease that affects about 2,000 people each year and can be fatal. In California alone, more than 8,000 human cases and 400 deaths have been recorded since 2003. Reducing its population could therefore save lives without harming the environment.

The principle of cytoplasmic incompatibility

This method relies on a peculiarity of the Wolbachia bacterium. When an infected male mates with an uninfected female, the sperm are modified in such a way that the embryos cannot develop.

By releasing a large number of infected males into the wild, we ensure that most uninfected females mate with them. Their offspring are then blocked, causing the mosquito population to decline over generations. This is a form of biological sterilization, without chemicals.

This technique is already used successfully in several countries against the tiger mosquito (Aedes albopictus) and the dengue mosquito (Aedes aegypti). Google is now applying it to a new species, Culex quinquefasciatus, which transmits West Nile virus.