To control rabies in wildlife, the USDA drops vaccine treats from the sky
EMILY KWONG, HOST:
You're listening to SHORT WAVE...
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REGINA BARBER, HOST:
A few months ago, Emily Mullin was going through her email - checking her inbox, deleting things - when she saw a press release from the U.S. Department of Agriculture - or USDA. Now, as a science reporter, Emily gets a lot of PR emails and press releases. But this one from the USDA Wildlife Services caught her eye.
EMILY MULLIN: For one, it was about this rabies campaign, and I was really intrigued because I didn't really realize that rabies was still a thing in the U.S., to be honest. It's something that I think is very feared, but I've never heard of anybody being exposed to rabies.
BARBER: And human cases of rabies are rare today. In the early 1900s, more than 100 people died annually from rabies in the U.S. By the end of that century, the number had dropped to 1 or 2. So why was this campaign Emily was reading about such a huge effort? As she kept reading, she noticed it was specifically focusing on vaccinating raccoons, an animal that has high rates of rabies. And although she knew raccoons could be rabies carriers, she was surprised to find that the campaign wasn't a one-time effort.
MULLIN: This is something that happens every year - that the U.S. government does and has been doing for a while now.
BARBER: Each year, tens of thousands of people are exposed to rabies in the U.S. - from raccoons, but also from skunks, foxes and bats. And so since the mid '90s, Jordana Kirby, wildlife biologist and field coordinator for the program, says the effort is unique because...
JORDANA KIRBY: It's the only program in North America where we're actively managing a wildlife disease at its source.
BARBER: But the part of the program that really stuck with Emily was how USDA officials get the vaccines to the raccoons. It's not through a syringe. It's through treats from above.
MULLIN: Government planes and helicopters drop around 9 million vaccine bait packets across the eastern United States.
BARBER: Today on the show - how the U.S. government delivers millions of sky vaccines in an effort to rid raccoons of rabies and why it may not be enough to eradicate the disease in the U.S. for good. I'm Regina Barber. You're listening to SHORT WAVE from NPR.
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BARBER: OK, so before the Wildlife Rabies Management Program was established in 1995, rabies was mostly managed by vaccinating pets and livestock. And now, Jordana, you're a project coordinator for the USDA's raccoon vaccination program. So let's talk about science for a minute, right? What causes rabies in humans?
KIRBY: So rabies is a virus. It's actually one of the oldest recorded viruses on human record.
BARBER: Wow.
KIRBY: And the primary way that a person is exposed to the disease is through contact and exposure with a rabid animal. And so in the United States, the primary potential cause of an exposure is now in wildlife. This has been the case for probably at least 3 or 4 decades. Prior to that, there were more rabid dogs and other domestic animals. But through required vaccination and leash laws, over time, that has changed. So fortunately, the number of rabid domestic animals is much less than it used to be historically, but we still see rabies in anywhere from 4- to 5,000 wild animals per year.
BARBER: OK. So take me through, like, the process. So, like, a rabid animal bites a human. How does that bite turn into disease? Like, what's happening in the human body?
KIRBY: So rabies is a neurological virus, so it attacks the central nervous system. And essentially what happens is - once an animal actually has rabies and develops clinical symptoms, it will cause an encephalitis. So it does impact the central nervous system and the brain. And the way that the virus is actually spread is through saliva. So the saliva or the actual central nervous system material, which would include brain, are the only ways that a person can be exposed. So generally, that's through a bite because the saliva contains the actual virus that can be transmitted.
And so I think one thing that probably a lot of people don't necessarily realize about rabies is that it is 100% preventable through postexposure prophylaxis or vaccines.
BARBER: OK. What is that vaccination series that you just said?
KIRBY: So the current vaccination series as part of postexposure prophylaxis would involve a single dose of what's called a human rabies immunoglobulin - or an HRIG - and that typically is injected into the actual wound site where the bite occurred. And then, following that...
BARBER: Wow.
KIRBY: ...There is a series of four rabies vaccines, the first of which is given on that first day, and then three additional vaccines that are given at another series of time. I believe it's at three, seven, and either 14 or 21 days post bite. And it's actually not quite as extensive as it was historically. It's now a much more shortened process, but an absolutely important and required one because even though rabies is 100% fatal, essentially, if symptoms do develop, it is also, through the safe use of those vaccines, 100% preventable.
BARBER: OK, let's get into the work that you do, then, at the National Rabies Management Program. Tell me about this program and how it got started.
KIRBY: Absolutely. So oral rabies vaccination in general was a concept that was developed in the 1960s. And by the late 1970s, field trials were first conducted in Europe, actually targeting red foxes in Switzerland.
BARBER: Ooh.
KIRBY: And so over the course of the next few decades, research was done in the United States. And we had the first field trials using an oral rabies vaccine in 1990 on a small island associated with Virginia called Parramore Island. And so the program, once that kind of proof-of-concept work was established in the United States, developed in the early-to-mid 1990s. And USDA really started to get involved around 1995. And at that time, we started to partner with states like Texas to begin oral rabies vaccination programs in Texas. And then, just two years later, in 1997, we began a program specifically in the eastern United States.
And so since that time, as raccoon rabies has sort of expanded along the eastern seaboard, our program has grown. And so currently, the program involves 13 states in the eastern U.S. as well as Texas. And in the East, we distribute millions of oral vaccines each year. We distribute them in rural areas by fixed-wing aircraft or airplanes. And in urban and suburban areas, we also fill in, essentially, those gaps with baiting by vehicle or by helicopter.
BARBER: And so this vaccine critters eat, right? So it's an oral vaccine. So you have to make sure the raccoons find them and want to eat them?
KIRBY: Yep. Yeah. We distribute these baits. In rural areas, we're focusing on wooded habitat and other habitats that raccoons and other wildlife are most likely to pick them up. And they have an attractant, of course, because if you just put a bait packet out, but there was no way to actually attract that animal, then they're probably not going to be interested in it.
BARBER: And by attractant, you mean, like, flavor?
KIRBY: Yes, sorry. Yes, the flavor. Yep.
BARBER: (Laughter).
KIRBY: So we've got the fish flavor, and then the other one is a sweet flavor. So you've got not quite salty and then sweet - the two different flavors - both of which work quite well for raccoons.
BARBER: Right.
KIRBY: Raccoons have much better sense of smell than we as humans do, so they can absolutely find them in the woods pretty easily and in urban areas as well.
BARBER: And these efforts to vaccinate raccoons against rabies - they've been successful?
KIRBY: The program has been successful. And so we have two kind of core program goals, if you will, the first of which is the goal that we're currently achieving, and that is to prevent any appreciable spread of specific rabies variants in the United States. And the focus on that is on preventing the spread of raccoon rabies in the eastern U.S. And then our second goal, which is more of a long-term goal, you know, where, literally, it's going to take us several more decades to accomplish, is to actually eliminate those specific variants. And so to eliminate raccoon rabies in the eastern United States would essentially involve marching it from its current extent, which is essentially along the Appalachian Mountains running from Maine to Alabama, and marching it all the way back to the ocean. That is our long-term vision.
BARBER: Wow. Are there any risks to those other animals if they consume them - like, even though they're consuming these things that are meant for raccoons, is it still safe for them?
KIRBY: Yes, the vaccine and the baits are safe for other animals. While our primary target in the east is raccoons, our feelings are absolutely not hurt if skunks, foxes or coyotes pick them up. And they do. And so although raccoons are the reservoir and spread rabies primarily in the East, those other animals, just like any mammal, can contract rabies. And in Texas, our program actually focuses on preventing rabies in coyotes and foxes. So it is a kind of multispecies program, if you will. And then as far as nontarget animals, which would be animals that we're not specifically trying to vaccinate through this program - they would not be harmed by it.
BARBER: Got it. OK. So this program targets raccoons. But like you said, they're not the only carrier. You know, bats are actually the leading cause of rabies deaths today for people in the U.S., right? So are scientists working on a vaccine for bats?
KIRBY: There is some research in bat vaccines or a potential way to try to manage rabies in bats. It is pretty complex. Part of that just has to do with bat ecology. They fly versus, obviously, you know, being land-dwelling animals like raccoons. There have been some studies done looking at, you know, whether there's some type of aerosol or something that can actually just physically be put onto a bat or several bats, and they can bring that type of vaccine back to their colony. But it's still sort of in the infancy stages. And so at this point, the best kind of mode of defense that we have as far as bats is education. Bats are amazing, and they're really important to our overall environment. You know, they eat insects, and they have so many other benefits to the environment. And so, you know, we don't want to scare people into thinking that all bats are bad. If someone has a bat in their home, it doesn't necessarily mean it's rabid. But if there's any potential concern about contact with a bat, then it's definitely important for folks to contact their local public health officials for a consultation just to see what the level of risk may be in that specific situation.
BARBER: Hmm. OK. So in your opinion - because, you know, you do this for a living - does it seem possible for the U.S. to eradicate rabies - like, either in raccoons or in general?
KIRBY: With our focus on raccoon rabies, I do think that's an attainable goal in time, but it's very difficult to get instant gratification. It takes time. It takes decades. And so I think with some of the other species that typically carry rabies in the United States, including bats as well as skunks, we're not as close as we are with raccoons.
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BARBER: One big success of the program is that it's prevented rabies from spreading to much of the Western U.S. And, as Emily Mullin, the reporter we heard from earlier, says, she sees another big success from the raccoon vaccination program.
MULLIN: In the U.S., the reason why we only have a few cases every year is because we have this hugely effective aerial campaign that I had no idea even existed up until shortly before I wrote this story. So in that sense, I think it's pretty amazing that there's this huge public health coordination to eliminate raccoon rabies.
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BARBER: You can find Emily's full story in our show notes, plus a link to her latest article, which came out yesterday, about the threat of rabies in vampire bats - a species expected to reach the southern U.S. in the next decade or two.
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BARBER: This episode was produced by Berly McCoy, edited by our managing producer Rebecca Ramirez and fact-checked by Anil Oza. The audio engineer was Ko Takasugi-Czernowin. Beth Donovan is our senior director, and Anya Grundmann is our senior vice president of programming. I'm Regina Barber. Thank you for listening to SHORT WAVE from NPR.
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