Stressed, hungry bat populations are linked to increased cases of emerging zoonotic diseases in Australia, new research has found. Bats have learned to adapt to more persistent food shortages by roosting closer to humans. This increases the risk of transmission of the potentially deadly Hendra virus from bats to horses to humans, according to a study published today in Nature.
“We want to keep the reservoir host [aka bat] happy”
Nonetheless, the study tells why it is important to protect bats, which have received an unfair stigma for exposing humans to novel viruses. At the end of the day, we actually affect each other’s ability to live in a healthy environment. This is part of the One Health concept that looks at the importance of plant and animal well-being to public health – as we saw last year in the US At the time, human outbreaks of Salmonella were linked to sick wild songbirds, as reported. New research published today shows how One Health is doing with bats in Australia. This may help identify ways to prevent the spread of disease through a phenomenon called “spillover,” when viruses jump from one species to another.
“We want to be able to keep the reservoir hosts [aka bats] happy,” said Raina Plowright, a professor at Cornell University and one of the study’s authors. under pressure [to] make sure we don’t see a spillover of events like Hendra virus.”
Fortunately, Hendra virus infections are still rare. In humans, it can look like the flu, but it can also be deadly because it affects the body’s respiratory and nervous systems. Four of the seven people infected with the virus have died since it was first identified in humans in Australia in 1994. They were exposed to the virus by treating or handling sick or dead horses, which in turn got the virus from bats. There are more than 80 documented cases of horse deaths from Hendra, although there is now a vaccine against them. The World Health Organization says it is “under investigation” for monoclonal antibody treatments in humans.
Image: Pa Tre Jones
This means there is no need to panic about Hendra virus right now. The study gives us a more complete picture of how bats, horses and humans interact, so we may be able to preempt even more worrisome viruses that no longer follow a similar pathway to Hendra virus from animals to humans . Hendra virus does not transmit easily from person to person, but if there is a related virus that is highly lethal and can be effectively transmitted from person to person—“and that virus is driven from nature to humans, then would be a disaster,” Plowright said.
For the study, Plowright and her colleagues analyzed 25 years of data from 1996 to 2020 on bat behavior, environmental changes, and transmission of Hendra virus from bats to horses The case is in Australia. They studied fruit bats known as flying foxes, which are extremely important to the African continent. Like bees, they are pollinators and feed on nectar. “Their whole face is immersed in these flowers, covered in pollen, which is just amazing,” Plowright told The Verge, describing the bright yellow faces of the bats after eating.
Bats can fly hundreds of kilometers overnight, spreading pollen great distances. This is critical to maintaining fragmented forests that have been cleared by human development. “[They] ensure that these forests remain genetically diverse and resilient, especially as we are changing our climate,” Plowright said. “They’re really the only animals that can maintain this level of resilience across large swathes of land.”
However, bats’ resilience is increasingly being tested – with implications for human settlements influences. Hendra virus does not cause overt disease in bats and is believed to have been circulating in bat populations longer than European occupation of Australia. It wasn’t until the 2000s that Hendra virus spillovers increased rapidly, coinciding with more deforestation and increased food shortages for bats. These food shortages have contributed to the overflow of Hendra virus clusters, especially in winter.
It starts with habitat loss and climate change making bats’ preferred food — flowers — even more scarce. The new study finds that these forces push bats to become less nomadic and instead choose to roost persistently near agriculture for a more stable food source. When bats forage where horses graze, the virus has the opportunity to jump from bat droppings to horses. Documenting this behavior is based on mounting evidence that deforestation and climate change increase the risk of viral spillover.
Still, what they found was surprising. During rare winter bloom events, the spillover effect all but disappeared as bats left their roost near humans and horses in search of their favorite food, the researchers found. “If you have winter blooms, the chances of a spillover effect is pretty much zero,” Plowright said. “When we looked at the data systematically, it was shocking.”
That’s a silver lining for Plowright. Provide bats with habitat so they always have food, and we don’t have to worry too much about them — or any viruses they might carry — becoming our pesky neighbors. It might look like planting a flowering tree, which bats prefer over what they find in farmland or urban areas. “We have this potentially very simple solution,” she said. “It’s achievable, it’s scalable, and it’s not expensive to implement. People are enthusiastic about it.”