Most of us fear bats that are in the news now as they are also natural carriers of coronaviruses.
We also typically associate bats with Batman in the cave, or even as blood-sucking mammals as depicted in films like Dracula. But what most of us may not know is that bats also help the world.
They pollinate plants, eat disease-carrying insects, and help disperse seeds that help with the regeneration of tropical forest trees.
Old relationship
The fact is that bats, as well many other mammal groups, happen to be natural carriers of coronaviruses. These coronaviruses don’t appear to be harmful to the bats, but there’s potential for them to be dangerous to other animals if the viruses have opportunities to jump between species.
Scientists, who compared the different kinds of coronaviruses living in 36 bat species from the western Indian Ocean and nearby areas of Africa, reveal that bats and coronaviruses have been evolving together for millions of years.
“Developing a better understanding of how coronaviruses evolved can help us build public health programs in the future,” says Steve Goodman, MacArthur Field Biologist at Chicago’s Field Museum and an author of a paper released in Scientific Reports detailing this discovery.
COVID-19 is just one variety of coronavirus
A lot of people use “coronavirus” as a synonym for “COVID-19,” the kind of coronavirus (SARS-CoV-2) causing the current pandemic.
However, there are a vast number of types of different coronaviruses, potentially as many as bat species, and most of them are unknown to be transferred to humans and pose no known threat.
Credit: Olivà S. Noroalintseheno Lalarivoniaina
The coronaviruses carried by the bats studied in this paper are different from the one behind COVID-19, but by learning about coronaviruses in bats in general, we can better understand the virus affecting us today.
The study
Goodman and his colleagues took swab and, in some cases, blood samples from more than a thousand bats representing 36 species found on islands in the western Indian Ocean and coastal areas of the African nation of Mozambique. Eight percent of the bats they sampled were carrying a coronavirus.
“This is a very rough estimate of the proportion of infected bats,” acknowledges Camille Lebarbenchon, Disease Ecologist at the Université de La Réunion.
The researchers ran genetic analyses of the coronaviruses present in these bats. “We found that for the most part, each of the different genera of families of bats for which coronavirus sequences were available had their own strains,” says Goodman.
“Moreover, based on the evolutionary history of the different bat groups, it is clear that there is a deep coexistence between bats (at the level of genus and family) and their associated coronaviruses.”
The team found that in rare cases, bats of different families, genera, and species that live in the same caves and have closely spaced day roost sites shared the same strain of coronavirus. Yet, they found it reassuring that the transmission of coronavirus in the region between two bat species seems to be very rare given the high diversity of bat coronaviruses.
Going forward
Learning how different strains of coronavirus evolved could be key for preventing future coronavirus outbreaks.
“Before you can actually figure out programs for public health and try to deal with the possible shift of certain diseases to humans, or from humans to animals, you have to know what’s out there. This is kind of the blueprint,” says Goodman.
Co-author Patrick Mavingui, microbial ecologist and head of the PIMIT Laboratory adds, “The development of serological methods targeting coronavirus strains circulating in the Indian Ocean will help show whether there have already been discrete passages in human populations, and their interaction with the hosts will allow a better understanding of the emergence risk.”
So don’t harm bats
Goodman notes that despite the fact that bats carry coronaviruses, we shouldn’t respond by harming or culling of bats in the name of public health.
“There’s abundant evidence that bats are important for ecosystem functioning, whether it be for the pollination of flowers, dispersal of fruits, or the consumption of insects, particularly insects that are responsible for transmission of different diseases to humans,” he says. “The good they do for us outweighs any potential negatives.”
The study was led by Université de La Réunion scientists Léa Joffrin and Camille Lebarbenchon, who conducted the genetic analyses in the laboratory of “Processus infectieux en milieu insulaire tropical (PIMIT)” on Réunion Island, focusing on emerging infectious diseases on islands in the western Indian Ocean.
