The link between environmental degradation, climate change, and the emergence of new viruses has never been more apparent than during the pandemic.
Arrival of SARS-CoV-2 and the spread of COVID-19 has brought much attention to how human activities such as deforestation can bring wild animals with the virus closer to people.
In a new study, researchers sought to provide granular data collected over 25 years in Australia to show the link between habitat loss, animal behavior, and viral spillover.
Specifically, the scientists looked at the bat-carrying Hendra virus, which primarily affects fruit bats (also known as flying foxes); the virus jumps into humans through horses.
“The combination of land-use change and climate now allows bats to persist in agricultural areas, where frequent food shortages lead to mass extinctions,” says biologist Peggy Eby of the University of New South Wales. Australia and colleagues have written in their published papers.
Zoonotic spillover describes how viruses and other pathogens found in animals jump into humans, sometimes with fatal consequences. The Hendra virus is one example; HIV, Ebola, rabies, and plague make up the list of other zoonotic diseases.
Hendra virus – named after the Brisbane area where it was discovered in 1994 – can cause serious or fatal disease in humans and horses. Usually, infected bats that feed on horses spread the virus, and since 2006, the number of Hendra viruses in Australia has increased.
In this study, Eby and his colleagues delved into decades to study rapid changes in bat behavior associated with Hendra virus spillover events in south-west Queensland between 1996 and 2020. residents.
“From about 2003 to 2020, bat behavior and the number of spillovers changed rapidly: the number of nests tripled, and 40 spillovers were found,” said Eby and colleagues.
Applying the data to a statistical model, the researchers showed how climate change and land use are driving bats into agricultural areas, increasing the risk of Hendra virus infecting horses.
By 2018, nearly a third of the natural bat habitat in 1996 had been removed, sending bats flocking to urban areas to roost, although most incidents (86 percent) occurred in agricultural areas where horses roam.
Drought-induced El Niño events also resulted in a shortage of winter food for bats, causing them to proliferate near populated areas where bats can find food.
Not only are food shortages and habitat loss pushing bats into areas inhabited by humans and horses — increasing the number of animals that come into contact with humans — but previous research suggests that nutritional stress can lead to increased viral load in bats.
“The timing of the Hendra virus spillover in the winter, months after the food shortage of the previous year, may be due to the increased stress of food that requires more energy in the winter (warmth and pregnancy) and the lack of resources in ‘insufficient space,’ the researchers write.
When the nearby forests bloomed more in the winter – which is increasing – the bats returned to their usual nomadic life, leaving the towns and agricultural areas in search of their natural habitat, and the destructive events did not occur during this time.
Protecting the remnants of native forests, especially the winter forest that provides food when food is scarce, “can be a sustainable, long-term way to reduce losses and protect the health of livestock and people,” the researchers concluded.
Reproducing similar research in other areas where zoonotic diseases are common could reveal the causes of these outbreaks and inform strategies to reduce the risk of disease.
But long-term data spanning several decades on viral reservoir hosts, particularly bats, are scarce. And even with our data, it comes back to the same problem: Humans are constantly destroying habitats and destroying ecosystems.
A 2020 study of nearly 6,800 habitats on 6 continents found that biodiversity is declining, and animals that survive and thrive, such as bats and rodents, are also more likely to harbor pathogens, putting them at risk of zoonotic diseases.
“We’ve been warning about this for years,” said Kate Jones, an ecologist at University College London who co-authored the study. Nature when it was published in August 2020.
No one was interested.
A recent study was also published in the Nature.