On a balmy morning in mid-August, Timothy Linder lifts the latch on a refrigerated trailer and opens both doors wide, releasing a wave of cold air heavy with the stink of fish guts.

“I don’t even smell it anymore,” says Linder, a wildlife biologist with United States Department of Agriculture’s Wildlife Services.

After hoisting himself up, Linder wriggles his hands into a pair of blue latex gloves, cuts into one of the stacks of cardboard boxes, and pulls out a plain brown block slightly larger than a miniature candy bar.

Thankfully, this snack isn’t for people. It’s for the raccoons.

“That’s a fishmeal polymer block,” Linder says, explaining the odor. “Inside, there’s a sachet, like a little ketchup packet, and the idea is that when a raccoon bites through this, it punctures the packet and gets a liquid rabies vaccine in its mouth.”

Most people don’t know it, but the U.S. government has been distributing oral rabies vaccines targeted at raccoons since 1997 as part of a massive public and animal health initiative. Called the National Rabies Management Program, it’s the largest coordinated effort to control a zoonotic disease in wildlife populations ever undertaken in the U.S.

The program costs about $28 million to run every year, but it’s estimated to save taxpayers $60 million in preventing the need for public health investigations, animal rabies tests, and access to post-exposure vaccines for humans. The idea is that the fewer wild animals that have rabies, the less likely it is that people, pets, or livestock come into contact with the disease, which is 100 percent fatal if left untreated.

Rabies is caused by a genus of bullet-shaped viruses known as Lyssavirus. And while there are different kinds, or variants, that tend to attack a certain host animal, like raccoons, skunks, or bats, any rabies variant can infect any mammal.

Humans are mammals, of course. And in much of the world, the canine variant of rabies remains a serious threat to human health, accounting for nearly 59,000 deaths each year. However, through widespread pet vaccination campaigns, the U.S. was able to eliminate the canine rabies variant in the late 1970s and again in the 2000s. Still, every ten minutes, someone in the U.S. receives treatment after coming into contact with other variants of the rabies virus, according to the Centers for Disease Control and Prevention.

The rabies virus is still out there, hiding in America’s wildlife.

Raccoon rabies free by 2053

“Annual statistics indicate that raccoons are one of the number one species in which we see rabies cases every year,” says Jordona Kirby, field coordinator for the National Rabies Management Program.

Raccoon rabies used to be confined to Florida and the Deep South prior to the 1970s. In their book, Rabid: A Cultural History of the World’s Most Diabolical Virus, Bill Wasik and Monica Murphy write, “But starting in 1977, more than thirty-five hundred raccoons were were legally trapped in Florida and shipped to private hunting clubs in Virginia, where they were released as prospective game.”

They brought raccoon rabies north with them.

So far, however, it’s stayed confined to the eastern part of the country. And for the last 20-some years, the U.S. has invested a lot of resources into making sure it stays that way.

Crazy History: How the Rabies Vaccine Came to Be A bite from a rabid dog was once a death sentence. Now, we have a 19th-century human experiment to thank for the rabies vaccine.

In 2019, the USDA and its partner agencies and organizations estimate they will distribute about 9.3 million raccoon rabies vaccine baits in a line roughly 25 miles wide that runs from Maine down to Alabama.

To be clear, the baits don’t cure rabies in animals that are already infected. Like any vaccine, they are preventative. But when eaten by enough raccoons, the baits create a herd immunity that gives the virus nowhere to go until, eventually, it fizzles out.

“The first goal was to stop the north and westward spread of rabies, and that’s been accomplished,” Linder says, as he loads several boxes of baits into the back of a car. “Next, we want to march the oral rabies vaccine line back to the East Coast and eliminate terrestrial raccoon-variant rabies altogether.” (Read more about how raccoons are spreading around the world.)

Drive-by baiting

After Linder distributes the vaccines to an army of trained local, state, and federal employees, the teams take to the streets to make sure the baits get to where raccoons can find them. This means hiking through Pittsburgh’s parks and bike paths, as well as driving methodically through each of the county’s 130 municipalities.

“Industrial areas are great for baiting,” says Jeff O’Brien, an administrator with the Allegheny County Health Department, while driving through Pittsburgh’s North Side. “You can toss them anywhere with high weeds or overgrowth.”

As O’Brien’s car creeps down a railroad, two other team members take turns tossing the baits out the window, pausing only to click the button on a Point of Interest Device that links each bait location to a satellite.

Wooded lots? Check. Overgrown roadsides? Check. Storm drains?

Wait, what?

“Storm drains are like raccoon superhighways,” says Henry Ma, one of O’Brien’s team members for the day and a Ph.D. student at the University of Pittsburgh’s Graduate School of Public Health. “Instead of crossing a road, they like to go underneath.”

In many ways, the effort to get rid of raccoon rabies may hinge on what happens here in Pittsburgh. That’s because as the line of vaccinated raccoons moves east from Ohio, Kentucky, Tennessee, and Alabama, Pittsburgh is the first major city it must pass through.

View Images Rabies can infect any mammal, but certain species like raccoons, skunks, bats, foxes, and coyotes now serve as a reservoir for the virus in the wild.

Photograph by Vickie Anderson, Nat Geo Image Collection

“We are going to be the model for how other cities do this,” says Lori Horowitz, an operations manager who oversees the Allegheny County Health Department’s partnership with the USDA.

But that model is still taking shape.

“The thought is if you can vaccinate 60 to 80 percent within a population, you can eliminate rabies on the landscape,” says Linder. “Right now, we’re not achieving that [in Pittsburgh].”

It’s not clear yet why the baits aren’t reaching enough raccoons, but Linder hopes the Point of Interest Devices will help codify the process. Introduced only last year, the technology has already been used to adjust the way baits are distributed across Allegheny County, which at around 170,000 vaccines represents the single largest hand-baiting exercise in the whole program.

It’s also possible that the vaccine itself could be more effective. But there may soon be a fix for that, too.

Health from above

Three weeks after the hand-baiting wraps up for the year in Pittsburgh, a white, double-propellered plane with blue and red stripes touches down at a wooded airfield in North Lima, Ohio.

As soon as the engine slows, half a dozen people jump into action, refueling the Beechcraft King Air A90 and restocking its hull with up to 15,000 army-green, vanilla-flavored blister packets.

As with the fish blocks, the wax packets also contain a raccoon rabies vaccine, but this version, known as the ONRAB Ultralite blister pack, may be the way of the future. After a series of field trials, the ONRAB vaccines are proving to be up to twice as effective as the other vaccines, at least when used in rural areas. Right now, the USDA is testing the new vaccines in five states, including Ohio, but Kirby expects they’ll get the go-ahead to use them more broadly within the year.

With a fresh crew and new payload, the plane zips up into the sky where it will go back to work blanketing hundreds of miles of forest and fields in rabies vaccines. A small conveyor belt inside the aircraft ensures the baits are distributed evenly, while a kill-switch allows the airplane’s navigator to account for houses, pools, highways, or any other areas that aren’t safe or effective to target.

“The planes fly from Lake Erie south to the West Virginia panhandle,” says Kirby over the mechanical growl of another take-off. “We have the ability to fly from sunrise to dark. It’s a pretty efficient process.”

It has to be. Up to 87 percent of the 9.3 million baits distributed this year will go out by way of airplane. Another seven to 10 percent are deployed via helicopters, which means only five to seven percent go out by hand.

In two days, Kirby and her team will break down the mobile command center in northwest Ohio and drive down to West Virginia to meet up with the fleet of A90s. Ohio is just the fifth stop on the north-south tour of the coast. By October, they’ll be flying over Alabama. But even then, the job isn’t done.

After another five weeks, the team’s biologists hit the field and start live-trapping raccoons to test their blood for rabies antibodies. If an animal has antibodies, it means the vaccines are working, and the more of them they find, the closer we get to eradication.

When they aren’t baiting or trapping, the National Rabies Management Program is analyzing distribution and surveillance data in preparation for next cycle.

“It’s definitely a year-round process when you put all of those puzzle pieces together,” says Kirby.

“Like planting a tree”

A 2016 study estimated that if the National Rabies Management Program were discontinued, it would take the raccoon rabies variant just twenty years to expand as far west as Wisconsin and Texas.

Still, even those who work on the project admit it can be difficult to get people excited about the program’s accomplishments and objectives.

“Our goal is to be raccoon rabies free by 2053,” says Richard Chipman, wildlife biologist and coordinator of the National Rabies Management Program. “But if you talk about 30-year planning horizons, people’s eyes glaze over.”

So Chipman likes to think of the effort to eradicate rabies “like planting a tree.”

“I’m almost 60,” he says. “If I plant an oak tree now, I’m not going to get the benefits of the oak tree, but I’m sure glad that the oak tree is growing.”

Even after working on rabies management for nearly 30 years, Chipman says he still marvels at how we’ve been able to develop and manufacture vaccines specifically for a wild animal and that we can essentially drop it out of the sky and make sure it gets into the mouth of a raccoon.