In danger of extinction, blacklegged ferrets receive experimental COVID vaccine

In late summer, as researchers accelerated the first clinical trials of COVID-19 vaccines for humans, a group of Colorado scientists worked to inoculate a much more fragile species.

About 120 black-footed ferrets, among North America’s most endangered mammals, have been injected with an experimental COVID vaccine aimed at protecting the small weasel-like creatures rescued from the brink of extinction four years ago. decades.

The effort came months before officials at the US Department of Agriculture began to accept requests from veterinary drug makers for a commercial vaccine against mink, a close cousin of ferrets. Farmed mink, raised for their precious fur, have died in the tens of thousands in the United States and have been slaughtered by millions in Europe after catching the COVID virus from infected humans.

Vaccinating these vulnerable species against the disease is important not only for the good of animals, experts say, but potentially for the protection of people. Some of the most pernicious human diseases have originated in animals, including the new coronavirus, which is believed to have spread from bats to an intermediate species before jumping to humans and triggering the pandemic.

The concern with animals like farmed mink, which are kept in overcrowded enclosures, is that the virus, contracted by humans, can mutate as it spreads rapidly among susceptible animals. which poses a new threat if it affects humans. In November, Danish health officials reported detecting more than 200 cases of COVID in humans with variants associated with farmed mink, including a dozen with a mutation that scientists feared could compromise the effectiveness of vaccines. However, officials now say this variant appears to be extinct.

In the United States, scientists have not found similar COVID mutations in populations of domestic farmed mink, although they recently noted with concern the discovery of the first case of the virus in a wild mink in Utah. .

“For highly contagious respiratory viruses, it’s really important to keep the animal reservoir in mind,” said Dr. Corey Casper, vaccinologist and CEO of the Infectious Disease Research Institute in Seattle. “If the virus comes back to the host animal and mutates, or changes, in such a way that it could be reintroduced into humans, then humans would no longer have that immunity. That worries me a lot.”

For newly vaccinated ferrets, the main risk is to the animals themselves. They are part of a captive population at the National Black-footed Ferret Conservation Center outside of Fort Collins, Colorado, where there have been no cases of COVID-19 to date. But the slender, furry creatures – known for their distinctive black mask, legs and feet – are feared to be highly vulnerable to the ravages of the disease, said Tonie Rocke, a researcher at the National Wildlife Health Center who is testing the ferret. . vaccine. They are all genetically similar, coming from a narrow breeding pool, which weakens their immune systems. And they probably share many of the characteristics that have made the disease so deadly for mink.

“We don’t have direct evidence that blacklegged ferrets are susceptible to COVID-19, but given their close relationship with minks, we wouldn’t want to know,” Rocke said.

Rocke began work on the experimental vaccine in the spring, as she and Pete Gober, black-footed ferret recovery coordinator for the US Fish and Wildlife Service, watched the reports of the novel coronavirus with growing concern. An exotic disease is “the biggest nemesis for ferret recovery,” said Gober, who has worked with black-footed ferrets for 30 years. “It can bring you back to zero.”

Ferrets are a native species that once roamed large areas of the American West. Their ranks declined precipitously over several decades, as prairie dog populations, the ferrets’ main food and shelter source, were decimated by agriculture, grazing and other human activities.

In 1979, black-footed ferrets were declared extinct – until a small population was discovered on a ranch in Wyoming. Most of these rare animals were later lost to disease, including the Woodland Plague, the animal version of the Black Death that struck humans. The species only survived because biologists rescued 18 ferrets to form the basis of a captive breeding program, Gober said.

With the threat of a new disease looming, Gober has doubled strict infection prevention precautions at the center, which houses more than half of the 300 black-legged ferrets in captivity. 400 others have been reintroduced into the wild. Then he called Rocke, who had previously created a vaccine that protected ferrets from Woodland plague. It uses a purified protein from Yersinia pestis, the bacteria that causes the disease.

Would the same technique work against the virus that causes COVID-19? Under the research authority granted by the Fish and Wildlife Service, scientists were free to try.

“We can do this stuff experimentally in animals that we can’t do in humans,” noted Rocke.

Rocke purchased the purified protein of a key component of the SARS-CoV-2 virus, the spike protein, from a commercial producer. She mixed the liquid protein with an adjuvant, a substance that enhances the immune response, and injected it under the skin of the animals.

The first doses were given in late spring to 18 black-footed ferrets, all males, all around one year old, followed by a booster dose a few weeks later. A few weeks after receiving the second injections, tests on the animals’ blood showed antibodies to the virus, a good sign – and waited.

In early fall, 120 of the 180 ferrets housed at the center were inoculated, with the rest remaining unvaccinated in case something went wrong with the animals, which typically live four to six years in captivity. So far, the vaccine appears safe, but there is no data yet to show whether it protects animals from the disease. “I can tell you we don’t know if this will work,” said Rocke, who plans to conduct efficacy testing this winter.

But Rocke’s effort makes sense, said Casper, who has created several vaccines for humans. Rocke’s approach – the introduction of an inactivated virus into an animal to stimulate an immune response – is the basis of many common vaccines, such as those that prevent polio and the flu.

Vaccines containing an inactivated virus to prevent COVID-19 have been tested in some animals – and in human vaccines, including CoronaVac, created by Chinese company Sinovac Life Sciences. But the effort in Colorado may be among the first to prevent COVID-19 in a specific animal population, Rocke said.

Gober said he was optimistic about ferret protection, but it will take a well-designed study to resolve the issue. Until then, it will work to keep fragile ferrets free from COVID-19. “The price of peace is eternal vigilance,” they say. We cannot let our guard down ”.

The most difficult task is to do the same for people, observed Gober.

“We are just holding our breath, hoping we can get everyone in the country vaccinated. It will give us all a sigh of relief.”