“After we detected it, we did a massive and extensive effort to prevent the mosquito from establishing and eliminate it,” says Jodi Holeman, the scientific services director for Fresno County’s Consolidated Mosquito Abatement District. “We were not successful, in any way, shape, or form.”
The county went from having not much of a mosquito problem at all to one that made residents avoid their backyards and porches. Unlike most mosquitoes, A. aegypti lives and breeds in places inhabited by people, laying its eggs in, say, the few droplets of stagnant water at the bottom of a wine glass left on a balcony, then hiding under beds and in closets, biting legs and ankles. This makes it much harder to fight. Going door-to-door and begging residents to dump out standing water wasn’t cutting it, so in 2016, Fresno teamed up with a scientist named Stephen Dobson and his company, MosquitoMate.
It was Dobson’s lab that figured out how to infect mosquitoes with a form of Wolbachia that’s different from the type of the bacteria that mosquitoes usually carry. That’s what makes the eggs unviable. MosquitoMate makes two species of mosquitoes infected with Wolbachia, A. aegypti and Aedes albopictus. Fresno became one of its test sites.
The initial Fresno trials were the first time male A. aegypti infected with the bacteria had ever been released in the U.S. The next year, Verily stepped in to help scale those efforts up, bringing more advanced technologies to the breeding and release process that would, they hoped, eventually make fighting mosquitoes massively scalable.
It seems to be working. This year, Verily signed on for a second season of releases. Two Verily trucks ply four different neighborhoods, hitting more than 3,000 homes. Over six months, the company released more than 15 million mosquitoes. Results from 2017 suggested the population of biting female mosquitoes dropped by two-thirds. This year, tweaks to the program have cut the mosquito population by a whopping 95 percent. A second project by Verily in Innisfail, Australia, that concluded in June reduced the mosquito population by 80 percent. This bodes well for eventually bringing the technology to other parts of the world—regions ravaged not just by itchy ankles but by deadly disease.
At first, Verily executives were worried about community resistance to fighting bugs with more bugs. So the company set up an outreach booth, complete with a cage full of male mosquitoes that people could stick their hands in to learn that males don’t bite. (Only female mosquitoes bite, which is why this and similar projects are careful to only release males.)
“We really appreciate you being here,” Clifford Lopes, a resident, told the company. “I brag to people about how I can sit on my porch now and not get bit.”
In videos of the original trials, you can see Holeman, the Fresno County scientist, gingerly blowing the mosquitoes out of a tube. The release van is now filled with proprietary technology, including software that determines exactly what areas of a neighborhood mosquitoes should be released in and a laser sensitive enough to count every single one as it exits, generating loads of data that can later be used to fine-tune the process.
At Verily’s headquarters, the “factory” where the mosquitoes are bred incorporates even more automation. Once the eggs are laid, robots rear the mosquitoes to adulthood, packaging them in containers filled with water and air, feeding them, and keeping them warm. Still other robots sort them by sex, first by size (females are bigger) and then optically, using proprietary technology. Mosquitoes are all given a digital identifier that makes it possible to follow them from egg-state to the specific GPS coordinate where they’re released.
With this year’s season wrapping up, the company has yet to decide whether it will further expand the program next year. Verily wouldn’t say how much it costs to manufacture and release tens of thousands of mosquitoes every day, but it’s a safe bet that it’s still an expensive proposition.