What If We Killed Every Mosquito On Earth?

A mosquito factory in Brazil is about to unleash five billion infected mosquitoes across the country for the first time ever. Is this the beginning of a sci-fi film or one of the most ingenious bits of science I've come across in a long time? Spoiler alert, it's the latter. We all hate mosquitoes, right? And not for no reason. On top of being a pure nuisance with their buzzing and itchy bites, they're actually the deadliest animal to humans. Literally, they kill more humans than any other creature, primarily through spreading disease. But before we can understand why scientists would want to make more of them, we should ask ourselves the question, couldn't we just destroy them all? Like, would it really be so bad if we killed every mosquito on Earth? Nature Journal actually did an analysis on this exact question and found that there wouldn't actually be a huge fallout if mosquitoes disappeared tomorrow. At least, not for humans. And even then, very few species heavily rely on mosquitoes. The ones that do, like some birds and fish, would likely replace them with something else. And while some mosquitoes do act as pollinators, there's nothing humans rely on them exclusively for. Of course, there's like 3,200 species of mosquito and only 200 of them bite humans, so it seems unfair to kill them all. But because of the ones that do bite us, around 247 million people are infected with malaria every year, not to mention a myriad of other diseases like dengue and zika. But while destroying mosquitoes may be a net positive for humans, one, is it really that feasible to do? And two, can we really know the ecological fallout from something of that magnitude? In comes the idea to make more mosquitoes in a factory, which sounds crazy until you realize it's not. You see, scientists have discovered a way to stop disease transmission from mosquitoes without the need for killing them. All thanks to a bacteria called Wolbachia. Wolbachia has sort of been in the background in mosquito biology, if you like, for the last 500 years, but only quite recently attracting a lot of attention. Some of the work that we did a number of years ago now showed that if you had Wolbachia in the mosquito that transmits viruses to people like yellow fever, chikungunya, dengue, the viruses couldn't grow very well in the mosquito if they had Wolbachia in them. This was confusing to the scientists at first, but they realized that the bacteria is likely out-competing any other pathogens like the dengue virus. So if Wolbachia is present, the virus is unable to proliferate properly and ultimately can't spread to humans. And if you take some of these Wolbachia infected mosquitoes and let them loose into the wild, they'll end up infecting other mosquitoes with Wolbachia. If an infected male mates with a non-infected female, the eggs she lays won't hatch. If the female has it and the male doesn't, her eggs will hatch, but they'll all be infected with Wolbachia and the same happens if both are infected. After a few generations, the number of Wolbachia-caring mosquitoes increases rapidly. We've done deployments in 14 countries. Usually our release programs last anywhere from a couple of months to maybe six months. And that provides the opportunity for those mosquitoes to mate with the wild mosquitoes and then pass Wolbachia into that wild mosquito population. Most importantly, dengue cases dropped significantly. One of the first comprehensive studies in Indonesia found the protective efficacy of the intervention was 77.1%. That's the equivalent of being four times less likely to develop the disease if you were in those areas. Now some test sites saw results as low as 38%, but that's still pretty major for the reduction of a disease. The lower results may be because it takes longer in some communities, depending on their size and environment, for Wolbachia to spread to the entire mosquito population. However, the most recent results from the Abura Valley, Colombia, which were just released in November 2023, actually saw a decline of 95 to 97% in dengue fever, bringing it to the lowest rate in 20 years for the region. What makes this result even more profound is that the rest of the Americas actually had the second worst year for dengue fever since 1980. So while some parts of Colombia were seeing record highs of dengue, this region, where modified mosquitoes were unleashed, saw record lows. This Colombia project began releasing Wolbachia-infected mosquitoes in 2015, so to see a 95% reduction in dengue fever is pretty astounding. And now the teams are trying to figure out how to deploy these modified mosquitoes as effectively as possible over even larger areas. Dengue is a huge problem in Brazil, as is Zika has been. We are working together to produce a facility that will produce up to 100 million mosquitoes a week in Brazil so that we can deploy them over multiple Brazilian cities. Now you might be wondering, are humans being infected with the Wolbachia in these mosquitoes? Like, is there a larger risk of having so much of it in our environment? So about 50% of all insects actually have Wolbachia. I can guarantee that you and everybody that listens to this will have been bitten by what we call the common house mosquito. That's the mosquito that's this indescript brown mosquito that will buzz around your ears, and that mosquito naturally has Wolbachia in it. If Wolbachia was a problem, we'd know about it. There's not a link between Wolbachia and any negative outcomes that anyone's been able to find. Currently, the WHO is evaluating this technology for use in other countries. Of course, the scientists involved see this as a supplementary measure and not meant to prevent or discourage dengue vaccines in the regions that are at high risk. But in the long run, it could end up saving hundreds of millions of people from being infected by dengue and around 100 million people from getting sick. It's all an amazing reminder how innovation and sometimes an unexpected approach can literally change the lives of hundreds of millions of people for the better. I want to send a big thanks to Dr. O'Neill for helping me to break down this incredible science. Thanks so much for watching. If you liked it, give it a thumbs up and subscribe for more science ASAP. Peace.