Will the Melting Permafrost Uncover Vector Borne and Zoonotic Pathogens and Release Ancient Infectious Diseases?
With melting ice and the release of ancient viruses, there are concerns around the emergence of potentially unknown infectious diseases. Emily Jenkins PhD, DVM, BScHon, offers insights on “zombie viruses” and says polar bears might hold the key to understanding what lies ahead, and how a One Health approach may help in surveillance and prevention.
For years, increased temperatures have been leading to climate change and concerns around rising ocean temperatures and glaciers melting and creating sea rise. Another less discussed climate concern has been the melting permafrost on land and the potential release of zoonotic and vector borne pathogens into the environment.
There are unique discoveries of extinct animals and other organisms from thousands of years ago being made today in the Arctic. In 2020, for example, investigators in Siberia stumbled upon a saber tooth cub, which they estimated to be 32,000 years old, was uncovered and it remained intact.1
Remains of a sabre tooth cub found in Siberia.
Image credit: National Geographic, Alexey V. Lopatin
Additionally, in Siberia, researchers uncovered what has been referred to as “zombie viruses.”
“We report the preliminary characterizations of 13 new viruses isolated from 7 different ancient Siberian permafrost samples, 1 from the Lena river and 1 from Kamchatka cryosol. As expected from the host specificity imposed by our protocol, these viruses belong to 5 different clades infecting Acanthamoeba spp. but not previously revived from permafrost: Pandoravirus, Cedratvirus, Megavirus, and Pacmanvirus, in addition to a new Pithovirus strain, which are characterized as viruses that have inactive for thousands of years,” investigators reported.2
“There's certainly been a lot of interest in recent times, and a lot of publicity around things like zombie viruses. So there's no easy answer to that. I think to start with, there are people giving this quite a lot of attention right now, certainly in the scientific world, also in the risk assessment world, and that includes things like national security,” said Emily Jenkins PhD, DVM, BScHon, professor and graduate chair, Department of Veterinary Microbiology, and head of the Zoonotic Parasite Research Unit at the Western College of Veterinary Medicine at the University of Saskatchewan, Saskatoon, Canada. “What we can say is that there's not a whole lot of evidence of spontaneous reemergence from the tundra right now.”
She does say the potential jump of these ancient viruses into humans and animals is still a very difficult transmission, especially as these pathogens may not survive.
“There was a nematode resuscitated from permafrost and was alive, a 40,000 year old roundworm. One thing to think about is that free living organisms are designed to survive more in the environment than pathogens,” Jenkins said. “Like the roundworms, are those so called zombie viruses. They're actually not pathogens of people or even animals.They're either free living or the viruses in particular, were actually viruses of amoeba. So it is quite a big stretch to jump from those things surviving to pathogens. The risk is not zero, but it's low probability.”
Polar Bears: The Proverbial Canary in the Coal Mine?
Jenkins has been studying organisms and animals in the melting permafrost and says there is evidence that can be gleaned from work with polar bears.
“We had this treasure trove of archived polar bear serum that stretched from the 80s, 90s, to the 2010s," Jenkins said. “We were able to take that set of sera and test it for exposure to a whole range of pathogens, including toxoplasma. We showed that over those decades, the amount of polar bears getting exposed was higher and higher—probably as a result of them losing sea ice, spending more time on land, and being more exposed to terrestrial pathogens.”
However, although nothing of concern has arisen from this in terms of older pathogens, she points to climate change issues affecting the Arctic, and the emergence of the modern-day vector borne viruses that could be a greater concern.
“One of the groups of pathogens we know are going to change with climate change is vectors and vector borne diseases. Some of the work that we did on those polar bear blood samples showed that they were increasingly exposed to these vector borne or mosquito borne diseases as they spent more time on land,” Jenkins said. “And interestingly, the female polar bears, when they're pregnant, they spend 8 months on land, vs the males, who only spend 3 months on land. So the females were way more exposed to these vector borne viruses. And when we started looking across the North American Arctic, from Alaska to Greenland, sure enough, these particular vector borne viruses, which people don't think of the Arctic as this hotbed of vector borne disease, but they were present in mosquitoes all the way from Alaska to Greenland. So that's another significant potential outcome of climate change: increased numbers of vectors that develop and more rapid development of both the vectors and the viruses.”
Utilizing the One Health Approach
Jenkins spoke at the recent IDWeek on this topic and says the environment is the biggest driver of changes and influences humans, animals, and pathogens.3
"So recognizing that the drivers are much bigger than us and our animals and wildlife is, I think, the message of One Health—which is that we're all in this together. Environment is driving massive changes, and we have some tools in our toolkit that we didn't used to have, in terms of surveillance and interventions. So I'm hopeful that One Health offers not the magic solution, but a solution to some of these really increasingly pressing challenges, especially as we see the climate change crisis and human health and socioeconomic crises all coming together globally.
