Whether we choose to fully acknowledge it or not, we live in a so-called “era of pandemics,” as experts have described it.
Outbreaks of zoonotic diseases — those caused by the transmission of a virus from animals to humans, such as COVID-19 and monkey pox — are likely to become more frequent, spread faster and cause more damage to the world than coronavirus did, according to a team of scientists who sounded the alarm with a major report in 2020.
The reason is our exploitative, invasive approach to the planet, which has resulted in us eating on land that was once dominated by wildlife, destroying biodiversity and forcing animals to find shelter and food elsewhere, often closer to humans.
This increased contact between wildlife and humans is a powder keg that could explode any moment in outbreaks of several new, deadly diseases, experts warn.
But because even the impending collapse of our climate cannot spur humanity to a significant, immediate change in the way we treat our planet, some scientists are exploring what other solutions are available to avert a future catastrophe.
Two biologists from the University of Idaho in the US have asked the question: If we know where these diseases can come from, why not act on their sources and vaccinate wildlife against these diseases?
How do we vaccinate wild animals?
“There are many ways to vaccinate wildlife,” Scott Nuisner, a professor of Biological Sciences and one of the authors of a study on the subject first published in Nature, Ecology & Evolution in 2020, told Euronews Next. .
“We are already doing this in North America and Europe to fight rabies,” he explained.
“For example, in North America, we vaccinate raccoons against rabies by dropping vaccines that sit in edible bait across the landscape from airplanes or helicopters. And the raccoons eat it and they get vaccinated against rabies. And that, of course, protects us and our livestock.” and our pets”.
This solution has proved quite successful, but Nuisner specified that in order for it to work, you need to have the right resources available – money to fly helicopters around and pay for the bait – and a species that is “long-lived”.
“Raccoons are short-lived from our perspective, but they are very long-lived compared to something like a rodent,” Nuisner said.
“If you vaccinate them, that immunity lasts for a while, whereas if you vaccinate something like a rodent population that could carry a contagious disease like hanta virus or lassa virus or some other nasty stuff, it’s really hard to do because you vaccinate them with that kind of conventional bait, and you get decent immunity in the population, but they reproduce so quickly that within a short time the immunity you’ve built up is washed away.”
This problem led scientists to look for a vaccine that, instead of being administered directly to wildlife, could pass from animal to animal.
Transmissible and self-spreading vaccines
Scientists have proposed two alternative ways to vaccinate wildlife: creating transmissible vaccines and transmissible vaccines.
A transmissible vaccine is applied directly to the animal’s skin or fur, which is then returned to its colony.
“So that when his friends are grooming, licking, cleaning — in a behavior called allogrooming that’s common in many different species of mammals — that vaccine goes to the next animal,” Nuisner said.
“There’s nothing about that vaccine other than what we’re already using. It’s incapable of self-replication; it’s just that the way you apply it makes it go from one animal to another.”
According to Nuisner, that’s something we can do now and that people like Daniel Streicker, a disease ecologist at the University of Glasgow, have already tested.
In 2017, Streicker and his team traveled to Peru to test transmissible rabies vaccines on vampire bats.
They found three colonies, each containing 200 animals, and coated the backs of 20 to 60 bats for each colony with a gel containing a biomarker that made the animal’s fur fluorescent.
Days later, the scientists saw that about 84 percent of the bats in all three colonies glowed, showing that the animals transferred the vaccine to each other.
Self-spreading vaccines, on the other hand, are much more complex. They consist of live modified viruses designed to spread an attenuated form of a disease within the animal population, thus spreading immunity.
“So, for example, we go into the rodent population that harbors a nasty infectious disease that can be transmitted to humans, and we find within that rodent population a benign virus that’s naturally in that rodent population,” Nuisner explained.
“We take that back to the lab and we put a little piece of the target pathogen’s genome in there, and then we put that back into the rodent.
“And when we do that, the hope is that it will be passed from rodent to rodent and establish immunity in every rodent against the target pathogen so we can control it in the rodent population so it never passes into humans.”
Also benefits for animal populations
Are these solutions already available? “In terms of performance [of these vaccines]”We’re still a long way off,” Nuisner said.
Transmissible vaccines can be implemented immediately, but there is a wider lack of funding and interest in them. But self-spreading vaccines aren’t ready yet, as the technology is still in the lab environment.
“To my knowledge, none of those have even moved to the field trial stage,” he said.
Vaccinating wildlife can help both animals and humans, Nuisner says, reducing the chances of them being blamed for the spread of disease.
“The way they control rabies from vampire bats in South America is often just to kill the bats,” he said. “So there are also these potential benefits to the wildlife: if you can eliminate the rabies, it reduces the incentive to go out and just kill the reservoir.”
Following the COVID-19 outbreak, experts reported a viral witch hunt against bats, which are natural reservoirs for coronaviruses, and the World Health Organization (WHO) recently condemned attacks on non-human primates in Brazil amid the spread of monkeypox.