The worst disease ever recorded, a live-frog pregnancy-kit, and a spike in malaria. They're all connected.
I want to start off by wishing you all a happy and prosperous Diwali (and Kali Pujo). May your days be filled with growth, wisdom, and happiness.
Readers of this newsletter know by now that I regularly write a science column for Hindustan Times (HT). Typically, I don’t just cover one research finding or story in the headlines. I’m grateful to Sukumar Ranganathan, Editor of HT for giving me a free rein to go down the rabbit hole and to discover connections hidden behind a single scientific story.
Stories in science are never complete. Through dialogue and conflict with other scientists. competitors, editors, and reviewers, they’re neatly packaged into scientific papers. Of the hundreds of thousands of papers that add to scientific knowledge, few are picked up outside their respective fields as “newsworthy”. Some are written up by press-offices. Others are communicated by journals themselves. They make a news-cycle with random quotes from authors and outside experts and strict word limits. And then they’re forgotten.
I wrote my 68th science column for Hindustan Times on a topic I’d been tracking for nearly two years.
Part I: The frog apocalypse.
While doing field work in Central America in the 1990's, biologist Karen Lips noticed the frogs she was studying were disappearing. Scientists in other parts of the world had documented the same thing - frogs and amphibians dying at an alarming rate.
The quivering voice of the scientist in the interview struck me. It was important to her to document the life of frogs that were almost certainly going to die out. Future generations would not know about many of the splendidly colored frogs and salamanders of North and South America. They were becoming extinct at an alarming rate.
COVID-19 is a devastating pandemic. But it does not threaten humans with extinction. Unfolding before our very eyes is a panzootic caused by chytrid fungus that is killing off entire species of frogs and salamanders.
As I write in my column,
A research article published in Science in 2019 tried to estimate the toll. In the article, scientists estimated that over 400 species of frogs and salamanders in over sixty countries have suffered due to the recent spread of chytrid fungus. Sadly, around 90 species had been wiped out forever.
A loss of this magnitude is difficult to imagine. Indeed, chytrid fungus may be the deadliest microbe ever described. One of the lead authors of the study, Jonathan Kirby, noted that “we’ve never before had a single disease that had the power to make multiple species extinct on multiple continents, at the same time… Hundreds, if not thousands of frog species could go extinct.”
How had this unthinkable tragedy occurred?
Part II: The pregnancy test.
The more I kept digging into the story, the weirder it got.
We don’t know the very early history, but some of the earliest cases of chytrid fungus were found in South Africa in African clawed frogs. These frogs were exported to different parts of the world for at least two decades in the early 20th century as a live pregnancy test.
It is a bizarre story that is now mostly forgotten. The story begins with scientist named Lancelot Hogben who discovered that female African clawed frogs could determine if a woman was pregnant. Urine from a woman was injected into a female frog. If the woman was pregnant, hormones in her urine would stimulate the frog to lay eggs. Apparently, this test was remarkably accurate, and thousands of frogs were shipped around the world for this pregnancy test.
Much later descendants of those frogs were found to harbor chytrid fungus, which they had acquitted some resistance to. While not the sole cause of chytrid fungus infection, these and other frogs that were traded certainly contributed to the spread of the disease globally.
The chytrid fungus has since decimated a large number of frog species on all continents, except in Asia. In 2018, a report in Science found that Asian amphibians were probably the original source of the fungus, explaining why some frogs developed some resistance over time But what really cause widespread devastation was a mutational event in the 1980s after which chytrid fungi became more virulent.
A scientist noted that many descendants of those frogs still harbored the virus:
"It's amazing that more than half a century after being brought to California, these frogs are still here, and they still carry this highly infectious disease."
Part III: The mosquito-borne deadly disease.
Now, you may not care about frogs. You may not care about the worst disease ever recorded, because it is in animals. But certainly you care about human health.
This is where the story takes another twist—
There’s a throughline from the loss of frogs because of chytrid fungus to an increase in malaria in humans. Take away amphibians that prey on insects such as mosquitoes and presumably their numbers explode leading to detrimental effects on human health.
Now, a research article published in Environmental Research Letters has found that the collapse of amphibian populations in Central America led to a surge in cases of malaria in Central America.
The new research is a stunning reminder that our health is inextricably linked to global trade animals and the environment. Disruptions in animal populations can shift the balance towards the spread of diseases in humans, even though the effect is not always immediate or direct.
After over two years of gathering information, this felt like a good time to share the story. But it is not over. No story in science ever is.
What else I’ve read:
“False teeth could double as hearing aids” at ScienceNews.
“All multicellular creatures interact with bacteria, but some have taken the relationship to another level with highly specialized structures that house, feed, and exploit the tiny organisms.” This is a lovely essay with gorgeous graphics.
"A dish of living brain cells has learned to play the 1970s arcade game Pong."
Everything you need to know about Highly Pathogenic Avian Influenza A(H5N1) virus — its disease-causing ability and transmissibility, published in a paper in Emerging Infectious Diseases
And this podcast episode isn’t strictly science, but it is the best thing I’ve heard all week.
Until next time.
Anirban