Endangered black-footed ferrets receive experimental Covid vaccine

About 120 black-footed ferrets, among the most endangered mammals in North America, were injected with an experimental Covid-19 vaccine designed to protect small, weasel-like creatures rescued from extinction four decades ago.

Vaccination of such vulnerable species against the disease is important not only for the sake of animals, experts say, but also potential for the protection of humans. Some of the most dangerous human diseases have occurred in animals, including the new coronavirus, which is believed to have spread from bats to an intermediate species before jumping to humans and triggering a pandemic.

The concern when it comes to animals such as farm minks, which are kept in crowded pens, is that the virus, contracted from humans, can move as it spreads rapidly to sensitive animals, posing a new threat if it spills back into humans. Danish health officials in November reported the detection of more than 200 cases of Covid-19 in people who had variants associated with farmed minks, including a dozen with a mutation that scientists feared could undermine the effectiveness. vaccines. However, officials now say the option seems to be gone.
In the US, scientists have not found similar Covid-19 mutations in domestic farmed mink populations, 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 very important to be careful with the animal tank,” said Dr. Corey Casper, a vaccinologist and executive director of the Seattle Infectious Diseases Research Institute. “If the virus returns to the animal’s host and moves or changes so that it can be reintroduced to humans, then humans would no longer have that immunity. That makes me very worried.”

For newly vaccinated ferrets, the main risk is for the animals themselves. I am part of a captive population at the National Black-footed Ferret Conservation Center outside Fort Collins, Colorado, where there have been no cases of Covid-19 to date. But thin, furry creatures – known for their black-eyed mask, legs and feet – are feared to be extremely vulnerable to the ravages of the disease, said Tonie Rocke, a research scientist at the National Center for Health. , which tests the ferret. vaccine. All are genetically similar, coming from a narrow reproductive pool, which weakens their immune system. And they probably share many of the characteristics that made the disease so deadly to minks.
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“We have no direct evidence that black-footed ferrets are susceptible to COVID-19, but given their close relationship with mink, we would not 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 U.S. Fish and Wildlife Service, tracked reports of the new high-alarm coronavirus. An exotic disease is “the biggest enemy for ferret recovery,” said Gober, who has worked with black-footed ferrets for 30 years. “It can even turn you to zero.”

Ferrets are a native species that once roamed vast areas of the American West. Their ranks have plummeted over several decades, as populations of prairie dogs, the primary source of food and shelter for ferrets, have been decimated by agriculture, grazing and other human activities.

In 1979, black-footed ferrets were declared extinct – until a small population was discovered on a Wyoming farm. Most of these rare animals were then lost to the disease, including the wild plague, the animal version of the Black Death that affected humans. The species survived only because biologists saved 18 ferrets to form the basis of a captive breeding program, Gober said.

Given the threat of new diseases, Gober has doubled its strict infection prevention measures in the center, which houses more than half of the 300 black-footed ferrets in captivity. Another 400 were reintroduced into the wild. Then he called Rocke, who had previously created a proven vaccine to protect ferrets from the wild plague. Use a purified protein from Yersinia pestis, the disease-causing bacterium.

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

“We can do this kind of thing experimentally in animals that we can’t do in humans,” Rocke said.

Rocke purchased the purified SARS-CoV-2 virus protein from a commercial manufacturer. She mixed the liquid protein with an adjuvant, a substance that improves the immune response and injected it under the animals’ skins.

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The first doses were given in late spring to 18 black-footed ferrets, all men, about a year old, followed by a booster dose a few weeks later. Within weeks of getting the second photo, animal blood tests showed antibodies to the virus, a good – and expected – sign.

By early autumn, 120 of the 180 ferrets housed in the center had been inoculated, with the rest remaining unvaccinated if something went wrong with the animals, which generally live four to six years in captivity. So far, the vaccine seems safe, but there are no data yet on whether it protects animals from disease. “I can tell you, we have no idea if it will work,” said Rocke, who plans to run effectiveness tests 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 – underlies many common vaccines, such as those that prevent polio and the flu.

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

Gober said he is optimistic the ferrets are protected, but a well-designed study will be needed to solve the problem. Until then, it will work to keep fragile ferrets free of Covid-19. “The price of peace is an eternal vigilance,” they say. We can’t let our guard down. “

The hardest task is to do the same for people, Gober said.

“We are holding our breath, hoping we can vaccinate all the people in the country. That will give us all a sigh of relief.”

KHN (Kaiser Health News) is a non-profit news service that covers health issues. This is an editorial program of KFF (Kaiser Family Foundation) which is not affiliated with Kaiser Permanente.