The hidden disease risks of modern housing developments in rural Africa

Tamika Lunn went to Kenya looking for bats. Her task, as a postdoctoral researcher in the lab of U of A biologist Kristian Forbes, was to catch bats to understand if, when and why they carried viruses. A spillover of a bat virus to humans could lead to the next global outbreak, like the COVID-19 pandemic.

Lunn noticed she had better luck finding bats in modern structures, with triangular roofs and made with finished materials, than in traditional ones, which had flat roofs and mud walls.

“I didn’t suspect this until I was physically in the country,” Lunn said.

That observation led to a systematic study of where bats in Kenya prefer to roost. The results were published in Frontiers in Ecology and the Environment. Lunn, the lead author and now an assistant professor at the University of Georgia, completed the work while working in the lab of Forbes, the study’s senior author.

Modern-style buildings were five times more likely to be occupied by free-tail bats, one of the most common species in the area. And buildings with triangular roofs, whether built with modern or traditional materials, were more than nine times more likely to have bats than flat-roofed buildings.

Sometimes thousands of bats would roost in a single house. Frequently, the weight of bat feces caused ceilings to collapse.

“Given the species that we’re looking at in Kenya, it’s not surprising they’re forming these big groups. But it is surprising that they’re forming these groups in buildings that are inhabited by people,” Lunn said.

Improved housing in under-resourced areas like Kenya is a top priority for the United Nations. And modern houses have been a boon to health, Lunn readily acknowledges. Malaria, respiratory illnesses and diarrheal diseases have been reduced. Mental health has improved. But when people have more contact with bats, they are more likely to be exposed to bat pathogens.

“They’re built in a way that doesn’t consider local bat ecology. That’s where we’re saying there’s a problem,” she said.

A spillover from bat to human could spark an outbreak that spreads far beyond Kenya.

Preventing the next pandemic

The Taita Research Station in Wundanyi, Kenya, where Forbes and his U of A team study bats and their pathogens, is surrounded by mountains topped with lush cloud forests. On the savannahs below, two national parks, Tsavo East and Tsavo West, are home to lions, antelopes, elephants and giraffes.

“It’s a really special part of the world,” he said.

He was drawn to the place not for its beauty but because it has the conditions to be a hotspot for a new disease outbreak. The area is rich in biodiversity. People often interact with the wildlife. Development has forced species like bats and rats to settle among humans. And the country’s vulnerable health system could let a new disease spread widely before it was detected.

He knows that bats carry pathogens. What he does not know is which pathogen could be the next to jump species and spread among humans, like COVID-19, the Marburg virus and Ebola. His lab focuses on detecting these pathogens and learning how they spill over to humans.

“How can we prevent that from occurring again, and that way prevent the next pandemic?” he said. “Bats are critical components of ecosystems. The answer is learning to coexist harmoniously with bats.”

The key lesson

In Kenya, locals have tried to rid their homes of bats in ways that are far from harmonious, and rarely successful. They have stuffed thorny plants into openings that bats use. They have tried killing the bats with pesticides, which can increase the numbers of pathogens in homes.

The best solution, Lunn said, is to properly seal a home’s access points, such as vents. But today in Kenya, like much of rural Africa, the materials to seal a home are not always available or might be prohibitively expensive. Providing those materials, and designing new homes so they keep out bats, should be a priority.

The bigger lesson, Lunn said, is that local context always matters. The ways things are done in one place may not work on the other side of the globe.

“That’s where you might get these unanticipated issues arising from otherwise good deeds,” she said.