Finding the answer to that question can help us discover new ways to fight viral infections in humans.
Scientists still do not know exactly what the origin of severe acute respiratory syndrome 2 (Sars-CoV-2) is, but one of the most popular hypotheses is that it came from bats. Researchers have already pointed out that these mammals and the coronavirus have lived together for millions of years. Additionally, bats can also be affected by other types of viruses, such as Nipah and Ebola. But after all, why are these animals more resistant to viruses than humans?
There are some explanations for this. According to a study published in the journal Emerging Infectious Diseases, bats release a lot of energy when they fly, causing their body temperature to be between 38°C and 41°C. The pathogens that evolved in these animals have adapted to withstand that heat. Our immune system has learned to use high temperatures as a way to kill pathogens, that’s why we have a fever. However, fever is not enough to kill a pathogen that has evolved to withstand high temperatures.
A team of scientists led by the Duke-NUS Medical School, in Singapore, has also identified genetic and molecular mechanisms that may explain why bats are so resistant to viruses that kill other animals. In the body of these flying mammals, the NLRP3 protein, responsible for activating an inflammatory response to fight infections, barely reacts when it encounters a viral load. Thus, the bat’s body is able to limit inflammation.
The human organism has a much more intense inflammatory response. When controlled, this mechanism is great for fighting infections; but it can also cause a lot of damage to our body.
A third study, published on the eLife website, brought one more hypothesis: to be able to attack the bats’ immune system, some viruses ended up learning to spread quickly through cells. So, by infecting animals that don’t have an immune system as strong as that of bats, these microorganisms end up causing more damage.
Scientists will continue to try to understand what is behind bats’ resistance to so many viruses that are lethal to other mammals. But they are sure of one thing: exterminating them is neither an option nor a solution.
Bats eat insects, which helps protect crops from pests. In addition, they are responsible for spreading seeds, such as fig trees, and for pollinating plants. Thus, to exterminate bats is to disrupt the balance of ecosystems.
Livia Loureiro, a researcher at the University of Toronto (Canada), points out that these animals can also bring the solution to Covid-19 and other diseases. For her, bats do not deserve the bad reputation they have and must be protected. “Even if bats are proven to be the source of this virus, they are not to blame for the transfer of SARS-CoV-2 — humans are. We destroy natural habitats at a frenetic speed; we kill threatened species, changing entire food chains; we pollute the air, the water and the soil,” she told The Conversation.