Even before their keepers enter the night house, the indoor enclosure where they sometimes sleep, Oakland Zoo brown bears Rubicon and Truckee know something is up. “They know we’re out here because they can smell us,” says Animal Care Keeper Erin Melroy. “They’re very smart, and they can pick up on the fact that ‘This is different, do I need to be worried?’”
Something is different: Today is the day Rubicon and Truckee will be vaccinated against COVID-19. The zoo is among the first of more than 70 animal organizations across the nation to administer donated vaccines from the animal health company Zoetis. The two-dose Zoetis vaccine, based on the COVID-19 spike protein, can be used across many species, from the zoo’s mountain lions and gibbons to its fruit bats and wolves. Rubicon and Truckee are part of a carefully planned vaccination effort that started on June 30 and will continue for the rest of the year, targeting the zoo’s most vulnerable animals.
The bears are in good hands. Melroy and her fellow keeper, Brittany Combs, have been working with them for weeks in preparation: letting them get used to the smell of the syringe, having them practice leaning against the mesh of the enclosure to be injected, getting them used to the poke of a capped needle. Today, settling into the dimness of the night house enclosure, the bears willingly present their shoulders and sit through the jab, in return for a reward of ice cream slurped off the scoop. Melroy compares it to the traditional lollipop many kids get after a shot. “No matter how much training we do, we can’t train away the pain,” she says. “We have to let them know it's worth it.”
Much like at human vaccination sites, Melroy and Combs stand by after the shot and watch their charge for 10 minutes, keeping an eye out for a swollen muzzle, vomiting, or difficulty breathing. Vice President of Veterinary Services Alex Herman is also on hand in case of emergency, with a box full of Benadryl and prednisone for potential allergic reactions, even though the only documented side effect from the vaccine so far is a gorilla with a headache. (Evident, apparently, from a very specific facial expression.)
After the 10 minutes are up, Melroy emerges victorious from the night house. “I didn’t get ice cream with my vaccine,” she says.
Herman smiles as she puts away her kit. “I think I got a ‘Neeeext!’”
Herman, who has worked at the Oakland Zoo for close to 17 years, realized early in the pandemic that she and her colleagues would need to take action to protect the animals under their care. Knowing that the virus likely came from bats, she was already on her guard; then news broke in April 2020 that several lions and tigers had gotten sick at the Bronx Zoo. Luckily, none of the Oakland Zoo’s animals has developed any symptoms so far. Herman credits the additional barriers the zoo put around ape enclosures and the personal protective equipment staff wear during training, treatments, and food preparation.
Meanwhile, on the other side of the country, Zoetis was also on alert. The company usually focuses on domesticated animals like cats and dogs. But as the virus spread in Denmark’s mink farms and prompted that country to cull millions of the animals, Mahesh Kumar, Zoetis’ senior vice president of global biologics, started to think again. When, in November 2020, the Department of Agriculture (which oversees animal vaccines in the U.S.) published a notice that it would consider applications for a COVID-19 mink vaccine, they decided to switch focus.
Zoetis had already developed vaccines against coronaviruses for multiple species, experience that helped them narrow down their options. Kumar’s team knew immediately they wanted to avoid the extra time and regulatory hurdles that would come with an mRNA vaccine, as well as the health risks of working with live viruses. “In half an hour we could make the call,” Kumar says.
They drew up a plan to develop a vaccine containing non-functional pieces of the virus, the SARS-CoV-2 spike protein, which would be synthesized in a lab. That decision ruled out non-injection delivery methods that require a live virus to work, like nasal sprays. (That might not have been realistic anyway. “Imagine trying to give a cat a nose spray vaccine,” Kumar says.)
Though the Zoetis vaccine was tested on dogs and cats and is being developed for mink, Kumar says it’s quite common, and in fact expected, for zoos to use vaccines off-label for other animals, with the approval of veterinary authorities. The vaccine’s two-dose regimen makes up for variability between animals and hopefully assures that animals of all sizes will get “enough” vaccine, from a grizzly bear to a red-tailed monkey.
The zoo’s initial shipment from Zoetis provides 50 double doses, covering about half of the 110 animals Herman has identified as in need of vaccination. Another shipment due in August will cover the rest. She and her staff worked mostly off clinical evidence—documented cases where a species or related species was infected—to make that list, which includes bears, Old World monkeys, hyenas, river otters, meerkats, wolves, and big cats like jaguars, lions, and tigers. She also plans to vaccinate the zoo's two types of fruit bats, even though bats are famously able to harbor many types of viruses without getting sick. “We’re aware they could maybe asymptomatically harbor different variants,” she says. Risking passing the virus back to staff is out of the question.
In a process similar to the emergency authorization given for human COVID-19 vaccines, once Zoetis demonstrated antibody response in vaccinated dogs and cats, the USDA awarded the company a conditional license to manufacture the experimental doses. For full authorization, Zoetis will also need to do “challenge testing,” which involves purposefully infecting test subjects with the SARS-CoV-2 virus, as well as “field trial” testing in commercial mink facilities. But for now, Kumar is pleased that his still-experimental vaccine will be helping animals across the country. “It’s important to understand, when you develop a vaccine in such a rapid manner that it’s not always a slam dunk,” he says. “We’re fortunate and thankful that we had this expertise and lucky it came together.”
After they identified their target species, Herman and her colleagues looked at the animals’ preferences to help plan their vaccine schedule. Because the zoo’s medical procedures are based on the animals’ willing participation, veterinary staff spend significant time tracking behaviors, gauging when an individual will be most receptive. The elderly tigers, for example, have blood taken frequently to help with monitoring and treatment of their kidney disease. The staff have noticed that “the older tiger ladies like something like 8:30 in the morning,” Herman says, while one mountain lion prefers after lunch, and the “lion boys”—a group of rambunctious teenagers who hang out together—are more likely to cooperate mid-afternoon.
Zoological Manager Andrea Gibson worked for weeks with a group of native Californian animals, including gray wolves, brown bears, black bears, and a jaguar, to get them ready for vaccination. Tolerating shots was a behavior they’d worked on before, since zoo animals need to be vaccinated often against diseases like rabies and distemper. Getting animal buy-in and not needing to fight against aggression or fear is key, she says. “It makes it easier on them, makes it easier on us, and they get a lot of rewards for doing it.”
Training for a vaccination usually entails breaking down the behavior into small steps and rewarding the animal for each success. For the larger carnivores, that usually means sitting quietly and presenting a shoulder or hip against the mesh of the enclosure, so a vet tech can reach it from the other side. (“It goes right into that muscle, like with humans,” Gibson says.) The animals get rewards for sitting; for leaning into the mesh; and for staying still during “sensitization”—in which they get used to a finger, then a closed syringe, then a needle touching their skin or fur.
In the case of the COVID vaccine, the animals also needed to acclimate to the presence of a new person (the vet tech, brought in to handle the vaccine itself) and the personal protective equipment staff needed to wear that might make them seem scary: goggles, facemask, gloves. At each step, the keeper used a signal or “behavior bridge,” in this case a whistle, to let the animal know it did a good thing and a reward was coming.
During normal training, that reward might be a tasty but standard item from an animal’s diet, but today is a special occasion. That means each successful animal gets a “jackpot” treat, or a snack of its most favorite food. Mountain lions get goat milk squirted into their mouths; Rubicon and Truckee the bears get their ice cream; Moses the alpha chimpanzee opts for M&M’s.
Ganesha and Hahnumahn are Oakland Zoo’s siamangs, mid-sized ape brothers with exceptionally long arms. They live on a lush island in the middle of a small green pond and do everything together: eating, sleeping, playing. Their keepers have even arranged for them to be vaccinated on separate days so they can care for each other.
Today it’s Ganesha’s turn. His brother keeps him company inside their night house as the vet tech and keepers prepare, chattering to him throughout the procedure. Ganesha’s reward is a giant marshmallow, which he eats in several dainty bites. After watching for any allergic reactions, the keepers open the night house door, and the two apes shamble across the wooden plank that serves as a bridge to their island, then settle in for a lazy afternoon munching vegetables and greenery.
As she prepares for her afternoon vaccinations—the “lion boy” teenagers are up next—Herman reflects on the role zoos have to play in conservation and education during a multispecies pandemic. For Oakland Zoo, she says, the key is a philosophy known as One Health, which sees human and animal health as intimately linked, so “to protect one is to protect the other.”
The primary goal of these vaccinations may be to protect her animals, she says, but “any advantages that flow from that are great.” That includes both educating the public about conservation and ecology and protecting it from disease. “We’re a conservation organization,” she adds, “and what that means is that all the beings on this planet, wildlife and the environment all need to be cared for because we’re all so interconnected.”