A cyclone can affect trees which impact insects and animals spreading diseases to people. Doctors are realizing that individual health is part of an ecosystem.
A bat, a flowering tree and a horse against the backdrop of a tornado. (Illustration by News Decoder)
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When she was studying fruit bats in Australia, Raina Plowright was surprised to discover invisible links among the bats, the tropical weather cycle known as “El Niño”, flowering trees and an infection called Hendra virus that kills horses and, sometimes, their trainers.
Experts struggled to explain how this close relative of measles was infecting horses in the first place.
A professor in the department of Public and Ecosystem Health at Cornell University, Plowright noticed populations of fruit bats periodically crashed. Bats that remained were weak and diseased, and often carried Hendra virus. Then her team found the flowering trees that the bats and bees usually fed from had disappeared.
“There’d been a large cyclone off the coast of Australia, and we think it probably diluted out all the nectar or stopped all the flowering,” she said.
Ultimately she was able to connect the cyclone to the trees the bats fed on and the migration of the bats to areas with horses.
The connections between animals, plants and the planet.
Plowright’s research and the questions that came out of it are part of a growing movement called One Health that’s helping people understand just how animals, plants, the climate, environment and people are linked.
What does a tropical cyclone have to do with the spread of a deadly disease among horses? What does healthcare have to do with the destruction of rainforests in Indonesia? What does social inequality have to do with the rise of drug resistant superbugs?
One Health research is showing that working in research silos is slower and less effective than taking a broader view of how the world works.
Take, for example, the widespread destruction of rainforests in Indonesia. Dr. Kinari Webb, founder of Health in Harmony, an international nonprofit, was worried about the fate of orangutans who lived in those forests.
She visited local residents cutting down trees to find out why they would destroy their own communities. Webb told me about her experience in an interview I did for the One World, One Health podcast sponsored by an organization called the One Health Trust.
“I was totally shocked when I found out the reason that many of the people were logging: to pay for health care,” Webb said. “I know one man who cut down 60 trees to pay for a C-section. One medical emergency costs an entire year’s income. So I had gone there to study orangutans; I was totally surprised by this revelation.”
Pests and people
Deforestation didn’t only hurt the orangutans. It helped spread disease in local communities, in part because the mosquito population exploded when trees disappeared. Webb changed her focus, went to medical school and returned to help provide health care to the residents.
“Amazingly, 10 years later, we had a 90% drop in logging households. We had stabilization of the loss of the primary forest that saved $65 million worth of carbon,” she said.
Trees, of course, absorb carbon dioxide, the gas that helps drive global warming and climate change.
“And at the same time, there were, across the board, improvements in health, including a 67% drop in infant mortality,” Webb said. “What that basically says to me is the communities were right: They knew exactly what the solutions were.”
The World Health Organization is embracing One Health as a desirable approach. Some universities, such as Canada’s University of Guelph, now treat One Health as its own distinct field of study while seeking to use the approach to link various specialties.
“We have to really talk to each other and One Health tells us that talking together is what is going to solve these problems,” said Sam Serrano, associate director of science communication for the One Health Trust. “It’s not just sitting in your laboratory by yourself.”
One disease and One Health
Serrano, who studied social science, says her discipline is helping her find new ways to talk to other specialists.
“When you talk to professionals from other areas who may not understand your area, you also learn how to talk to the public,” Serrano said. “And also you have to think about the world in a different way. And the other person needs to think about the world in a different way.”
The term “One Health” started being used after the emergence of the first SARS, the outbreak of severe acute respiratory syndrome in 2003 that killed around 800 people before it was stopped.
SARS was caused by a coronavirus, a relative of the COVID-19 virus, and was eventually traced to animals sold for food in an exotic market in China. Those animals were almost certainly infected by bats, which carry a range of coronaviruses.
People clearing forests and hunting in dense jungles for rare delicacies to sell had released a never-before-seen virus. They were just trying to make a living, but the consequences went far beyond their world and their poverty.
It’s probable this is how COVID-19 originated, as well.
“We are really just approaching health in a way that understands and acknowledges that you can’t solve these problems just by focusing on one sector,” Serrano said. “We can’t stop the spread of disease from animals to humans without looking at both animal health and human health.”
And it’s also vital to consider social and cultural factors, including poverty and inequality.
Global health threats
The World Health Organization says antimicrobial resistance — the rise of bacteria, viruses, fungi and parasites that resist the effects of drugs used to fight them — is one of the most urgent global health threats facing humanity.
“A lot of time when we talk about issues like drug resistance, people just look at it from behind a microscope,” Serrano said. “But they need to look at it from a perspective of people who need to take the drugs.”
She said that people who don’t have a doctor or access to running water to wash their hands, will be more likely to get infections.
“We need to get out from behind the microscope,” Serrano said. “We need to talk to people. We need to find out the reasons behind these major global health problems by looking on the ground.”
In her study of bats in Australia, Plowright found an interaction between climate, habitat loss and the health of farm horses.
“Whenever there was a moderate to extreme El Niño year, there was always a food shortage for bats and for bees the following year,” Plowright said. To make matters worse, forests had been cut down to make room for towns, cities and farms.
How a disease can jump from bats to horses
The bats in Australia, which usually lived far from people, moved into urban areas.
“Importantly, they moved into agricultural areas where there are horses,” she said. But fruit bats don’t bite animals, so how did they infect the horses?
Plowright thinks they were feeding on fruit trees, and either their guano was infecting horses grazing underneath the trees, or perhaps they left saliva on half-eaten fruit that the horses then nibbled.
It took a cross-sectional approach to understand the complex interaction of climate, plants, animals and people, she said. And until scientists, politicians, doctors, community leaders and educators all start to embrace a broader approach, people will be left in the dark about how one seemingly random event has severe health consequences.
“We’re not investing in understanding the natural history of these viruses, the drivers that are forcing the viruses into human populations,” Plowright said.
Three questions to consider:
- How might climate and human health be linked?
- How do political systems affect the way the world studies the spread of disease?
- What other kinds of problems might a One Health approach help solve?
Maggie Fox has been reporting on health and science for more than 25 years and is currently a contributing writer to the Fuller Project and host of the One World, One Health podcast. She has covered conflict, politics and other international events from London, Hong Kong and Beirut. She has covered the cloning of Dolly the sheep, Ebola epidemics, stem cell technology, vaccine controversies and other stories for Reuters, CNN, National Journal, Medscape, STAT and NBC News. She lives outside Washington, DC.
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