The Decades-Long Quest to Make Virus-Proof Mosquitoes

A bacterium called Wolbachia could stop the bloodsucking insects from spreading diseases like Zika and dengue fever.

A small box labeled "Aedes aegypti / Wolbachia" and "Dengue"
Pilar Olivares / Reuters

In the summer of 1922, as Simeon Burt Wolbach and Marshall Hertig slid their scalpels into 13 common house mosquitoes, they had no idea that they were about to stumble across one of the most successful microbes on the planet, nor that a century later, their discovery could potentially save millions of lives.

In those dissected mosquitoes, the duo found a new bacterium, and 14 years later, Hertig christened it Wolbachia after his colleague. Having named it, they ignored it. But in the subsequent decades, long after Wolbach’s death in 1954, scientists started to realize that his bacterial namesake is omnipresent, devious, and powerful.

It infects around four in 10 species of insects and other arthropods, which are themselves the most diverse and numerous animals in the world. It manipulates the sex lives of its hosts, changing some from males to females and allowing others to clone themselves, all so that it can spread quickly into the next generation. It even contains multitudes of its own: Nestled within its genome is a virus, and hidden within that virus are genes that originally came from spiders.

Wolbachia also makes some of its hosts resistant to viruses—a quality that a team of Australian scientists, led by Scott O’Neill, have spent decades trying to harness. When they implant the bacterium into the mosquito Aedes aegypti, the insect can no longer transmit the viruses behind dengue fever, yellow fever, Chikungunya, and Zika. And best of all, the bacterium is so good at manipulating its hosts that it can rapidly spread through a wild population. Release Wolbachia-infected mosquitoes into the wild, and within months, all the local bloodsuckers change from carriers of disease into culs-de-sac.

This approach, which I’ve written about before, is now being tested in 10 tropical countries around the world. It’s testament to the value of research for the sake of it: There was no way Wolbach and Hertig could have predicted where their arcane explorations of mosquito carcasses could have led.

The project also shows just how long it takes to translate basic discoveries into life-changing tools: It took decades for O’Neill’s team to successfully inject Wolbachia into mosquito embryos, to show exactly how the bacterium acts against viruses, to simulate its spread among wild insects to show that their approach could work in the field, and to get all-important community support for their work. You can watch their quest in the video below—the fourth in a series of online films produced by HHMI Tangled Bank Studios, which adapt the stories in my book, I Contain Multitudes.