Masindi, Uganda — Tobacco farming in Uganda has resulted in the loss of trees key to the diets of chimpanzees and baboons, increasing human-primate interactions — and the risk for disease spillover.
Less than half a kilometer from Aliyo Sarile’s tobacco farm, the wild frontier of Budongo Forest rises, a wall of emerald canopy and untamed vegetation marking a boundary.
Each dawn, Aliyo wakes to nature’s orchestra: birds chirping, chimpanzees hooting through the trees, and baboons barking commands — a soundtrack that registers as neither nuisance nor entertainment in his daily life.
But the forest’s balance has shifted. Chimpanzees and baboons now regularly emerge from their leafy realm to raid Aliyo’s land, devouring his crops and fruits, sometimes trampling his vulnerable tobacco seedlings under their curious hands and feet.
When these wild neighbors appear, Aliyo shouts or waves a sturdy stick to reclaim his territory.
“I try not to touch them or where they have touched because I know that these animals can spread diseases,” he says.
These unwanted visits are not random.
Over a decade ago, responding to an increasing global tobacco demand, local farmers stripped Budongo Forest of its Raphia farinifera palm trees to make curing strings, unknowingly eliminating a critical source of minerals essential to the primates’ diets.
This ecological disruption led primates to consume bat feces, which according to a 2024 study published in Nature contains numerous concerning viruses, including some related to SARS, the coronavirus family that spawned COVID-19.
This seemingly innocuous dietary shift has created what experts now recognize as a potential pathway for devastating bat-borne viruses to jump from wildlife to human populations, setting the stage for a devastating spillover event, not long after COVID-19 upended lives across the world.
A vast army of viruses silently circulates through the animal world, and sometimes these breach the biological barriers between species, infiltrating human bodies and triggering disease. Deadly outbreaks throughout history, including the plague, Spanish flu and COVID-19, started in animals before spreading to humans. Scientists call this zoonotic spillover.
Uganda stands at a particular crossroads of this viral vulnerability, frequently battling outbreaks of Marburg, mpox and Ebola. Most recently, the country grappled with an Ebola outbreak that began in January.
As of now, even though there’s no clear sign of danger in the animals or human settlement potential around Budongo Forest, Uganda needs to be prepared, says Dr. Deogratias Sekimpi, a public health expert and technical adviser at Uganda National Association of Community and Occupational Health, a local nongovernmental organization.
“Early detection is the real challenge,” says Henry Kyobe Bbosa, incident commander at the Ministry of Health, who helped manage Uganda’s response to COVID-19, mpox and the Ebola Sudan outbreak. “The easier part is that when we have the outbreak declared, the rest of the other response mechanisms are activated and quickly put in place.”
In this forest, humans and wildlife routinely share the same resources, creating pathways for pathogens to cross species barriers.
“People come to fetch water from the ponds inside the forest, the very source that animals get water from,” says Simon Peter Ogola, a forest ecologist and research training coordinator at Budongo Conservation Field Station.
Triggers of new diseases — deforestation, hunting, urbanization, climate change and industrial farming — are well documented by scientists, but it’s not always clear how these activities create pathways for pathogens to jump between species. The precise biological chain reactions can remain hidden in ecological blind spots.
In Budongo, the Nature study reveals a clear chain: tobacco demand led to deforestation, which forced dietary changes in primates.
And while Uganda’s tobacco farming declined after the 2015 Tobacco Control Act, production has recently spiked, with 32,965 metric tons in 2022 rising to 33,600 in 2023, and projections of 35,600 metric tons by 2028. This growth worries experts about further deforestation.
There are an estimated 75,000 tobacco farmers in Uganda. In 2023, Uganda exported US$67.9 million of raw tobacco, making it the 10th most exported product in the country, according to data from the Observatory of Economic Complexity.
Adule Benon represents the new wave of tobacco farmers, having started in 2023. To cure his harvest, he sometimes collects wood from the forest, though he buys strings from the community.
Over the years, tobacco has become more profitable than maize for farmers, Adule says.
Like many locals, Adule routinely enters the forest for household water and firewood while forest animals, especially the chimpanzees, make reciprocal visits to human settlements. “Sometimes I see them in the forest. Sometimes they come and feed on the mangos found on trees in my homestead,” he says.
A 2015 study found that major changes in land use in the Budongo and Bugoma forest reserves have shifted the relationship between local communities and chimpanzees, from co-existence to conflict. As trees disappear from the forests, encounters between people and chimpanzees have increased.
“This relationship is marked by conflict, particularly when chimps and baboons venture beyond forest boundaries to compete with children for mangoes, bananas and jackfruit,” Ogola says. “We document roughly 10 attacks annually, with chimpanzees primarily targeting children under 10 years old.”
Nakisanze Segawa is a Global Press Journal Reporter-in-Residence based in Kampala, Uganda.
Micheal Ezati Nyakafunjo translated some interviews from Lugbara and Swahili.
