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You’ll probably never get rabies, but that doesn’t make it any less terrifying. The disease is virtually always  fatal once symptoms emerge.

And while we have some post-exposure treatments, they rely on getting to the doctor in time. So a much better solution would be  to prevent rabies in the first place. And to do that, it’s animals that we need to figure out a better solution for.

Because they’re the ones  who often transmit it to us. Which is extra complicated when we want to curb the spread of rabies due to vampire bats. Since their whole deal is biting other animals, stopping them from spreading  rabies along the way isn’t easy.

But new research shows the solution to vampire bat rabies might be an  ingredient in your hot cocoa. [♪INTRO] Rabies is an RNA rhabdovirus  found in the Lyssavirus genus. It almost always passes to  humans via an animal bite, and it can take days to months  for symptoms to show up. These include headaches, vomiting, confusion, fear of water, and  hallucinations, all of which are thanks to the virus infiltrating  the central nervous system.

Once symptoms do appear, the  patient dies within 2 or 3 days of going to the hospital,  basically 100% of the time. A last ditch effort is the Milwaukee Protocol, where doctors put the patient  into a medically induced coma, pump them with antivirals, and hope for the best. But only about a couple dozen  people have survived, and they often have major neurological  deficits after all’s said and done.

And it’s not just human lives on the line either. Cattle are frequent rabies victims, with economic impacts in the  tens of millions of dollars. So preventing their infections  could save their lives, and also all the beef, dairy,  and money that comes with them.

Which is why researchers have  started looking into ways to better control rabies before  it gets to us, or to our cows. One of the major reservoirs for  rabies, particularly in Latin America, is vampire bats. So many scientists have focused their rabies-control efforts  on those little bloodsuckers.

Vampire bats den in close quarters, love a good slobbery grooming session, and have been known to  regurgitate and share meals. Which means rabies can  spread throughout the colony faster than head lice in an elementary school. The other issue is their diet.

Vampire bats are obligate sanguivores, meaning they only drink blood. So to chow down, they have to bite  other animals like humans or cows, which is how they spread their  rabies outside the bat colony. So if we could get a handle  on the rabies in vampire bats, it would help control the disease  among many species all at once.

Also to be clear, the bats aren’t necessarily asymptomatic reservoirs of the disease. They can suffer and die from rabies too, which means that eradicating  rabies in bat populations would make them feel better in the process, too. A lot of attempts at controlling  bat rabies have taken the scorched earth approach  of just killing as many of them as possible, since a dead bat can’t bite.

One of the most popular  methods of bat-murder takes advantage of their natural  instinct to groom each other. Scientists apply anticoagulant  paste to some of the bats' backs, then as they lick each other clean, that poison spreads all around the colony. Once they ingest the anticoagulant,  their blood can’t clot anymore.

It’s like if Buffy the Vampire Slayer swapped out her wooden stakes for a topical warfarin. That method can kill essentially 100% of bats, so you can’t say it isn’t effective. But some researchers fear that once the bats notice group mates dying, they panic and scatter, which means any rabies  they’re carrying would spread beyond the group, potentially  making the rabies problem worse.

Plus, not everyone’s onboard  with killing a bunch of bats or releasing warfarin  paste into the environment. And we’d be in trouble if  the bats took a page from the rat’s playbook and started  developing resistance to warfarin, which we know happens in other species when we try to use the drug as pest control. Luckily, bleeding hearts and worried  scientists alike can rest assured that newer efforts have shifted  toward vaccination, not elimination.

But before we get to that, all  research needs funding, even ours. So here’s a quick ad break. Thanks to Squarespace for  supporting this SciShow video!

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Head to Squarespace.com for a free trial, and when you’re ready to launch, go to www.squarespace.com/SCISHOW to save 10% off your first  purchase of a website or domain. The idea of finding alternative  rabies solutions besides vampiricide has been kicking  around for a few decades now. But early attempts focused on capturing the bats, having them fast for a bit, then syringing vaccinated blood into their mouths.

Which is… fine. But since you  can’t capture every single bat and force feed them the vaccine, that  solution doesn’t scale very well. Baiting their food with the vaccine  isn’t an option, since like I said, their diet is exclusively  blood, straight from the source.

And you can’t bait a living  animal with a high enough concentration of the vaccine  that it’s transmissible by blood. So these rabies vaccines need  to look a little different, because not only is it impossible  to catch and vaccinate every bat, they’re also not the most compliant patients. That puts researchers at risk of being injured and getting rabies themselves.

Instead, researchers want to revamp  the same hack that’s been used to spread poison, by getting bats  vaxxed through grooming each other. A 2008 study looked at coating  bats in literal Vaseline that had the rabies vaccine mixed  in, and they found that in the lab, this did work to spread the immunity around. But subsequent experiments  suggested that Vaseline, or really any petroleum jellies,  might not be the right vehicle.

For one thing, this vaccine needs  to be stable in tropical climates, since the ideal place to roll  it out would be Latin America. And when Vaseline gets too hot, it gets runny, meaning that it tends to  just drip right off the bats. For another, the Vaseline itself isn’t the best at preserving the vaccine’s structural ingredients, meaning it gets degraded and won’t work as well.

Not to mention, have you ever licked Vaseline? It’s not a great feeling, and  the bats don’t think so either. They’ve tried other mediums like glycerin gel, but ran into a lot of the same  problems, especially with melting.

But the concept was solid,  even if the gel was not, which is why an international  team of researchers created their own special gel  optimized for vaccine delivery. It was a customized carboxymethyl  cellulose or CMC gel. Essentially, modified plant cellulose.

CMC gels are already used in  things like eye lubricants to help give them the right  viscosity, so the researchers just tweaked it to be edible bat hair gel instead. And yes, CMC gels are edible, too. They’re even used in hot cocoa, to give your drink that perfect mouth feel.

The researchers mixed the vaccine into the CMC gel and added a fluorescent biomarker. That way they could come back  to snag some bat hair samples, check for fluorescence, and quickly determine if the bats ingested the vaccine or not. They estimated that they applied the paste to around one fifth of the colony.

After releasing them back into the  group and letting them lick away for a while, the researchers  checked for fluorescence to see how many bats got their  dose of vaccine from grooming. Based on that sample, they  estimated that 88% of the colony slurped up some vaccine  and was now immune to rabies. Each of the initial treated bats spread  the gel to more than 3 other bats on average, which was better than  in their earlier gel formulations.

And way better than vaccinating  bats one at a time by hand. It was a huge improvement over previous versions, and worked well even at hotter temperatures. The cherry on top is that  mathematical models suggest this kinder method could  be even more effective than the previous gold standard  of “kill the dang things”.

The researchers hope that  this approach to immunization continues to be investigated in field studies, or even applied to other species of bats. So hopefully in the future, bats  themselves will start taking a bite, or a lick, out of their own rabies problem. I’d raise a cup of cocoa to that! [♪OUTRO]