Vaccinating bats could be good for people. But how would you do it? : NPR

Bats such as this greater horseshoe bat can harbor dangerous viruses. Researchers present new evidence that it may be possible to immunize winged mammals to protect them – and us – against potentially fatal diseases.

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ByAgostini/via Getty Images

Here’s a question you may never have asked yourself: How to vaccinate a bat?

You can’t just ask your local veterinarian. Bats won’t line up alone outside a clinic, either.

But a group of Chinese researchers think they have an answer, which could prove to be a new way to stop the spread of diseases transmitted from animals – such as bats – to humans.

“Bats carry many very deadly pathogens such as the Ebola virus, NipahHendra, the coronavirus and also the rabies virus,” says Aihua Zhengvirologist at the Chinese Academy of Sciences. “People are discovering more and more viruses transmitted by bats.”

When such viruses are transmitted to humans, the results are often fatal. So it’s very worthwhile trying to avoid fallout in the first place.

In some parts of the world, this has led to organized killing of bats. “But when people kill the bats, they essentially have more contact with them,” says Zheng. “There is more chance[s] be infected.”

And eliminating bats can have other consequences. These flying mammals play an essential role in the environment by pollinating plants and controlling harmful insects. And they are already threatened by loss of habitat and their own illnesses.

Now, in an article published in the journal Scientific advancesZheng and his colleagues offer evidence for a different solution to the spillover problem: vaccinating the bats themselves against these dangerous viruses. “We protect not only humans, but also animals,” says Zheng.

They used several techniques to immunize bats, including using vaccine-carrying mosquitoes!

“The advantage is that if we immunize the population, the transmission of the virus will be reduced, or even eliminated,” he adds.

The approach is still in its early stages, but is an exciting development for people battling these diseases.

The Skeeter Strategy

Zheng explains that the challenge of this approach was how vaccinate bats.

In a study a few years agoFor example, researchers applied a topical vaccine to bats’ fur so they could lick each other. Zheng says it worked in the lab, but “it’s not easy to scale in the real world. You have to catch a lot of bats and then release them.”

Instead, Zheng and his colleagues chose to recruit a squadron of tiny syringes on the wings: mosquitoes. “We want to make the mosquito a vaccination tool,” explains Zheng. In particular, they feed mosquitoes with blood mixed with genetically modified vaccines against one of two deadly viruses: Nipah and rabies. These vaccines then appeared in the mosquitoes’ bodies and in their salivary glands.

To see if a mammal would pick up the mosquito vaccine, his team conducted some of their experiments on mice and other rodents. But the big tests took place with real bats. One of the first steps was to capture insectivorous bats in the suburbs of Beijing. “I like to explore the cave,” says Zheng.

In the laboratory, the researchers exposed the animals to the special insects in two ways: either the mosquitoes bit the bats or the bats ate the mosquitoes.

A few weeks later, when researchers took blood from the bats, they found antibodies. Zheng says this means the animals had developed an immune response to the virus corresponding to the vaccine they had been exposed to.

The researchers then infected the bats that had developed rabies antibodies with the real rabies virus. Such an infection would normally have been a death sentence. But for these bats, “most of them survived,” Zheng says.

One day, he imagines releasing these modified mosquitoes into caves where they could vaccinate wild bats. He plans to use a constant flow of air at the entrance to trap insects inside while allowing bats to come and go freely. He hopes that after a while, most of the bats will be vaccinated.

Drink

Zheng acknowledges that the anti-mosquito approach wouldn’t work everywhere. “The real world is complicated,” he explains, making it difficult to release engineered insects into all environments. So the researchers developed a plan B: a saline solution containing an oral rabies vaccine, which the bats in their laboratory easily swallowed. “So when the bat drinks[s] water, they will be vaccinated,” explains Zheng.

This also protected the animals from later infection with rabies. “Yeah, it really worked!” he said. “I’m pretty excited about these results[s]”.

“It’s an astonishing study,” says Ausraful Islamveterinarian and infectious disease specialist icddr,ba health research institute in Dhaka, Bangladesh. He did not participate in the experiments.

Islam recognizes that if this approach succeeds in the wild, it could be a real boon. for countries like Bangladesh that are battling bat-borne viruses. “They have [a] a promising avenue for developing vaccines [for] different animals,” he adds, “but I think there is still work to be done before large-scale applications” – such as exploring how long immunity lasts in bats and how feasible it would be for different countries to set up a rolling bat vaccination campaign.

As for Zheng, he and his team are already planning future studies and looking for international collaborators to help bring this crazy idea to life.