Parasites

This Bacterium Could Be The Magic Bullet For Mosquito-Borne Diseases

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Which animal kills the most people every year? If you said shark, you're way off. Same with bears and lions. No, the deadliest animal in the world is smaller than your pinky nail: it's the mosquito, which kills an estimated 725,000 people annually by infecting its victims with a range of diseases. They're also notorious jerks. Scientists are hard at work trying to find a way to stop these life-threatening pests, and they may have hit the jackpot with a genus of bacteria called Wolbachia.

Transmission electron micrograph of Wolbachia within an insect cell.

I've Got A Fever, And The Only Prescription Is More Wolbachia

There are a few ways you can cut down on mosquito-borne diseases. You could give people vaccines against the diseases themselves, but that's quite a challenge in developing countries, and anyway, vaccines for some diseases don't even exist yet.

You could try killing all of the mosquitoes, but we've attempted that, and the bugs developed a resistance to the insecticide (which was carcinogenic to boot).

So you're left working with the mosquitoes to make them less deadly. If you bred them to be sterile, they'd produce fewer offspring. Alternatively, if you could come up with a tiny vaccination against the diseases they spread, they could go on reproducing without killing so many humans. Well, we have good news: Wolbachia can do both of those things.

Wolbachia is a parasite that invades its host's cells and messes with cell division, which helps it spread through the body's tissues. One tissue it likes best? The reproductive organs. In females, it wriggles its way into the eggs, passing itself onto future generations. But here's the best part: when an infected male's sperm mingle with uninfected eggs, Wolbachia keeps the new cells from dividing properly. That means an infected male can't produce offspring with an uninfected female, rendering the males functionally sterile.

But that's not all. Wolbachia can also block the spread of Dengue fever, a disease without a cure that's commonly nicknamed "breakbone fever" for the crippling pain its sufferers endure. Wolbachia is one reproduction-halting, disease-fighting powerhouse of a parasite.

Mosquito Larvae

Fly, My Pretties

Scientists are already using Wolbachia's superpowers to their advantage. One issue with the super-parasite is that it doesn't naturally infect the species of mosquito responsible for all those terrible viruses, Aedes aegypti. That means that scientists have to actually breed new mosquitoes infected with the parasite and release them into the wild. In 2016, the Google company Verily announced that they would do just that.

The Debug Project raises about a million Wolbachia-infected male mosquitoes a week in an automated lab, and releases them into the wild. Male mosquitoes don't bite, so they're harmless to humans. The first test groups of about 20 million mosquitoes were released in Fresno, California in July 2017 — the largest field trial to date — and the company plans to perform more trials in different environments to prove that it can be done anywhere. Someday, we may see the end of mosquito-borne diseases, and when that day comes, we'll have a microscopic parasite to thank.

The Debug Project

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