Baby southern elephant seals were among the first to die when a deadly strain of bird flu arrived in the Crozet Islands in 2024. But as the virus spread across the sub-Antarctic archipelago, a handful of penguin chicks had a potential advantage: They had been vaccinated against the flu.
Ecologist Thierry Boulinier and his colleagues were about to conclude a small vaccine trial in young king penguins on the archipelago’s Possession Island when the virus arrived in October. A series of H5N1 epidemics which swept the globe in 2022killing birds and mammals, including bald eagles and red foxes, was an “obvious motivating factor” in starting the trial, says Boulinier, of the Center for Functional and Evolutionary Ecology in Montpellier, France. Vaccinating vulnerable wild birds such as the northern rockhopper penguin or the Amsterdam albatross could protect them from the deadly virus.
This project is one of many aimed at leveraging vaccines to protect endangered species from devastating diseases. In September, Australian authorities approved a chlamydia vaccine for use in wild koalas. Vaccines against a deadly herpesvirus that causes bleeding disease in elephants are showing promising results in some zoos. And researchers are vaccinating bats in the western United States against white-nose syndrome, a fungal disease that has killed millions of bats nationwide.
Vaccines can be a critical conservation tool, says Tonie Rocke, a wildlife biologist at the United States Geological Survey’s National Wildlife Health Center in Madison, Wisc. As habitats shrink, animals interact more frequently with each other, providing new opportunities for the spread of pathogens. “Their environment has changed, just like ours,” Rocke says, “and diseases are spreading all over the world at a rate that would not have happened in the past.”
Vaccines are not a silver bullet for stopping outbreaks, in part because they can be expensive to develop and deploy. Yet researchers are making progress toward using this technology to protect wildlife from deadly infectious diseases.
Early trials suggest protection against spread of bird flu in Antarctica
H5N1 arrived in the Antarctic region for the first time in October 2023on Bird Island, off the Atlantic coast of South America. A year later, the virus appeared about 5,800 kilometers to the west on Possession Island in the southern Indian Ocean, where Boulinier’s team was testing its vaccine.
Dozens of southern elephant seal babies and adults have died across the rainy and windy archipelago, along with brown skuas, snow albatrosses and gentoo penguins. The virus also killed hundreds of king penguinsthe team reported in September in Natural communications. Although this represents only a small fraction of the tens of thousands of king penguins that live in three colonies across the island, Boulinier says, “we cannot say how many of them might die in the future if the virus reappears.”
In February 2024, the team vaccinated 30 king penguin chicks and followed up with a booster dose a month later. The results are promising: the immune penguins have developed an immune response without any dangerous side effects, the researchers reported in a paper published in September on bioRxiv.org and forthcoming in Natural communications.
It is not yet known whether the vaccine protects seabirds from the disease, as none of the vaccinated chicks became infected during the outbreak. Additionally, the need for two doses makes vaccinating many animals at once “far from ideal,” Boulinier says. But the team plans to test single doses and is launching a new trial in adult king penguins to determine how long immune protection might last.
Thanks to vaccination, king penguins join a short list of creatures that researchers are seeking to protect from bird flu. Critically endangered California Condors and New Zealand kākapōsthe only flightless parrot, is among the avian species that have developed an immune response against the virus in small vaccine trials.
Avian flu vaccines have also shown great promise in marine mammals, says Dominic Travis, a veterinary epidemiologist at the Marine Mammal Center in Sausalito, California. He and his colleagues vaccinated endangered northern elephant seals and Hawaiian monk seals, with the animals developing an immune response that the team believes is protective. So far, Travis said, “it’s all good news.”
Long-awaited shot could reduce major threat to koala survival
Last year, Australia’s veterinary medicines regulator approved a vaccine to protect endangered koalas against chlamydia, a milestone a decade in the making.
Cattle chlamydiaa bacterial infection that can cause blindness and infertilityis just one of many threats koalas face, says molecular biologist Nina Pollak of the University of the Sunshine Coast in Queensland, Australia. But other stressors, like habitat loss and climate change, can make chlamydia infections worse. “If [koalas] “If you’re stressed, they’re less resistant to disease,” says Pollak. Vaccination can give them a better chance of survival.
Antibiotics are usually the first choice for treating bacterial infections. But these drugs can kill the gut bacteria that koalas rely on to detoxify toxic eucalyptus leaves, their only food source. “They have become weak and unfortunately it’s a death sentence,” Pollak says.
The vaccine is primarily intended to prevent marsupials from developing serious chlamydia infections. “It’s not a magic cure,” Pollak says. On the one hand, the vaccine is not 100 percent effective; the blow reduction in koala mortality by 64%researchers reported in npj vaccines in August. On the other hand, it may be difficult to reach populations who need the vaccine most.
Wild koalas admitted to hospitals and sanctuaries for treatment can receive the vaccine upon arrival, but finding koalas in their natural habitat is not easy. “They live in trees and these are areas that are difficult to access,” says Pollak. Finding them would require a lot of people, traps, detection dogs and possibly drones, which can be costly. The team is also seeking funds to manufacture and distribute the vaccine.
Although the first doses might be available this year, Pollak says, “there may not be a lot of doses. Not everyone will probably get them, but we will try to distribute them equitably.”
Young elephants could one day be protected from deadly virus
In February 2024, two Asian elephants at the Cincinnati Zoo contracted a deadly virus. Both survived.
Elephant endotheliotropic herpesvirus, or EEHV, kills 60 to 85 percent of animals that develop a horrific viral hemorrhagic disease, making it the leading cause of death among young Asian elephants in North America and Europe. But a few months before the Cincinnati Zoo’s elephants became infected, they received a new vaccine.
The two elephants had mild infections and neither required treatment, the zoo reported in July. “These cases mark the first documented cases of natural exposure following vaccination, suggesting that the vaccine may prevent severe disease. »
Various forms of EEHV naturally infect almost all Asian and African elephants, says Lauren Farris, an immunologist at Baylor College of Medicine in Houston. “It’s not really about whether they’re going to get it or what their chances are of catching it. They’re going to get it eventually.” Not all elephants become seriously ill, but infections can be particularly risky for young Asian elephants ages 2 to 8 years old.
Calves under 2 years old have antibodies from their mothers that attack the virus, says virologist Paul Ling, whose Baylor lab developed the vaccine. But this protection eventually disappears. It is possible that without their mother’s antibodies, EEHV could cause an “uncontrolled infection” that the young elephants’ immune systems struggle and fail to control. A vaccine could help their bodies prepare and make infections less deadly.
The long-term goal is to protect free-roaming wild elephants, Ling says. It is unclear whether hemorrhagic disease is as deadly in the wild as it is in captivity, although some wild elephants have died from it. “This [vaccine] is part of the toolbox we will need to help preserve and maintain this species.
But EEHV vaccines are not yet ready for large-scale use. Ling plans to monitor the elephants that have been vaccinated so far — some of which have not responded as well as the Cincinnati Zoo’s elephants — and vaccinate other elephants under human supervision. A different vaccine provoked an immune response and was found to be safe in the first completed trial on adult Asian elephants in captivity, researchers reported in October in Natural Communications. The next step is to test this vaccine on its target population: calves.
Success against fungal disease offers hope for endangered bats
A fungal infection puts northern bats at risk of extinction. White nose syndrome, caused by the fungus Pseudogymnoascus destructanshas killed millions of bats in North America since it was first detected in 2006. The fungus grows on the skin of mammals and wakes them intermittently while they hibernate, forcing the bats to burn energy they must survive the winter. Among the a myriad of tools that researchers are developing To protect bats, an oral vaccine currently in field trials is showing promise.
A little brown bat (Myotis lucifigus) receives an oral vaccine against white-nose syndrome, a disease that has devastated bat colonies across the United States.
Sin Rocke“The fact that we were able to develop a vaccine for a fungal disease is pretty remarkable,” says Rocke, a USGS wildlife biologist. “There isn’t even one approved for humans at this point.”
Rocke and colleagues reported in 2019 that vaccinated little brown bats were less likely to develop skin lesions or die than control bats. Since then, the team has vaccinated more than 5,000 wild bats of various species. In 2023, they vaccinated a Wyoming colony of long-eared bats, a species listed as endangered due to white-nose syndrome. This year, more northern long-eared bats in South Dakota and Montana will also receive the vaccine. “We could lose this species,” Rocke says. “It’s not clear. But everyone is making an effort to prevent this.”
These field trials, conducted primarily in the western United States, suggest the vaccine can protect wild bats, Rocke says. While bats in the East and Midwest are developing resistance to the disease, bat populations in the West are more vulnerable. This is because populations, and the bats themselves, are much smaller. “The disease costs a lot of energy during hibernation,” says Rocke. “It’s the very small bats that suffer the most.”
Signs that the vaccine is working give Rocke some hope, and the team will vaccinate as many bats as possible. “Sometimes these kinds of interventions are really necessary if we want to conserve a species,” Rocke says. “There are good conservation reasons for vaccinating animals, and we would not do it if it would harm them further.”
