The fungus, ophiocordyceps unilateralis, commonly known as the ‘zombie-ant fungus’ in the popular HBO television series The Last of Us, is real and can zombify ants and spiders.
But could ants, or other insects spread fungi and cause a human apocalypse?
University of Guelph entomologist, Aaron Fairweather, says it's not likely.
“Having these thoughts, especially after the COVID-19 pandemic, I’m not sure this helps,” Fairweather said.
"The Last of Us does a good job of bringing up the fear of zombification and having this fungi that can control people. But the actual transfer of fungi from an insect or a spider to that degree, it is highly unlikely.”
Fairweather says most insects don’t have associations with humans.
"They are also physically and molecularly distinct from humans. The exception, of course, are those insects that feed on us,” Fairweather said.
According to Fairweather, insects like mosquitoes, bed bugs, kissing bugs and ticks have evolved to feed on human blood. As a result, they can produce infections such as yellow fever, Chagas disease and malaria.
“We have a lot of the same basic components of a nervous system and muscles. But the molecular differences are so pronounced. It wouldn’t be very reasonable for a fungi to be able to infect us and then spread to all of the centres of the body which would be necessary to cause this same kind of control,” Fairweather said.
Additionally, Fairweather says that from a basic level, insects are exothermic, which means that they must rely on the temperature of their physical environment to regulate their internal body temperature."
The Last of Us is an American post-apocalyptic television series based on the 2013 video game. The series is set in 2023, twenty years into a global pandemic caused by a mass fungal infection which forces its hosts to transform into zombie-like creatures, devastating society.
Fairweather says there are other fungal diseases that already parasitize humans.
“There are issues that could arise with fungal diseases but not particularly in this way, from insects. Most fungi evolve alongside their prey and are quite species-specific. Fungi that evolve to prey on cold-blooded animals such as insects likely wouldn’t survive the switch to warm-blooded ones,” Fairweather said.
“Parasites like ophiocordyceps unilateralis have to overcome their host’s immune system, behavioural adaptations and internal pH in order to grow. This results in an evolutionary arms race between the host and parasite: the host to develop better immune systems to overcome the parasite, and the parasite to overcome their immune response in turn.”
In most cases, Fairweather says, the host wins the battle.
Fairweather is currently a PhD student in the School of Environmental Sciences at the Ontario Agricultural College. Their research focuses on eusocial insect behaviour, including colony establishment and foraging as well as the sublethal effects of neonicotinoid pesticides on bees and ants.
“I have always had a passion for insects and entomology. I’ve been studying this since I was three years old,” they said.
Fairweather grew up in New Brunswick.
“My dad is quite the academic. He went to school for a lot of different things and he encouraged me to pursue anything that I am fascinated with about the natural world. He kept fostering it in me and I kept going,” Fairweather said.
When in middle school, Fairweather picked up Steven Marshall’s The Ants of Eastern North America.
“That was the bible for insects in Canada at the time. I looked up where Steven Marshall was teaching, and it happened to be at the University of Guelph,” Fairweather said. “And that’s how my academic journey started. I’ve done all three degrees at the University of Guelph. I love this campus.”
Fairweather has watched The Last of Us and has also enjoyed playing the video games.
“The story really intrigues me. There are scary things that the show brings up. The opening scene with the scientists talking about diseases that could impact humans, that is what has stuck with me,” Fairweather said.
“They talk about the fact that global climate change is impacting species tolerances, and that is certainly a reality. We are seeing some fungal diseases that are able to persist in warmer temperatures, and this is actually starting to allow them to infect in different places, to transfer and move faster."
Additionally, Fairweather says recent research indicates that humans are conditioning themselves to live in warmer climates.
“Because we have our own self-contained micro habitats in the form of our houses, we don’t have to heat ourselves as much anymore, and so the internal body temperature of humans has been decreasing over the past couple centuries by quite a bit,” Fairweather said.
“In 2006, there was an interesting case study done on fungal pathogens that started to infect humans that didn’t before. This was because some people have a low enough base of homeostasis and they were able to be infected by a whole slew of new fungal diseases.”
So, Fairweather says, these issues are happening in the real world, and in a really real sense.
“It’s not cinematic as this zombified fungus that can control you and turn you into this ravenous beast that wants to bite everybody, but it’s very real that a pandemic could happen where a fungus suddenly reaches our immune system,” they said.
Fairweather has always had a passion for insects, especially ants.
“Ants have a whole lot of interesting behaviours and ways to control pathogens that humans can pay attention to. They’ve been living in their own societies for millions of years and have had to deal with the consequences of close body contact and the transfer of disease a lot longer than we have,” Fairweather said.
“Ants are very picky about cleanliness and colonies rarely collapse due to infection.”
Fairweather says before re-entering nests, ants clean themselves with specialized saliva to disinfect themselves from spores such as Ophiocordyceps unilateralis, and they are constantly washing and cleaning up after themselves to avoid disease.
“Even if insect-preying fungi suddenly became capable of spreading to humans, we could look to ants for an example of how to adapt. Rather than a fear of what ants could transfer to us, they are a great case study in how to protect ourselves against disease,” Fairweather said.
“We can learn a lot from them.”
