The role of bats in the appearance of the virus called into question by an Israeli study

The bat has been in the dock since the start of the Covid-19 pandemic. However, Israeli researchers believe that there is not enough evidence to incriminate him. On the contrary, the bat would present a balanced immune response against viruses that have evolved over millions of years.

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[EN VIDÉO] A bat answers the ringing of a telephone
Researchers have trained wild frog-eating bats, Trachops cirrhosus, to associate a ringing phone with a treat. Four years later, they still remembered it. The video first shows an untrained bat just wriggling at the sound of the bell ringing. Then comes the trained bat which, at the sound of the telephone ringing, goes to get its treat. Evidence that the animal has a long-term memory. © College of Natural Sciences

More than two years after the start of the pandemic of Covid-19, we still do not know for certain its origin. Among the animals involved, the bats have a bad reputation, considered reservoirs of agents pathogens viral, including SARS-CoV-2.

Is the bat really an animal reservoir of viruses?

A meta-analysis conducted by researchers at Tel Aviv University reveals many cases in which they believe there is not enough evidence to blame these mammals. ” When considering the interaction of bats with virusthe time seems ripe for a paradigm shift “, they write in the study published in iScience. First, they wondered if bats were indeed reservoirs of viruses. A reservoir animal is defined as a population in which the pathogen can be permanently maintained and from which the infection is transmitted to the target population.

Although more than 100 bat-associated viruses have been identified as important to emerging and re-emerging human infections “, the researchers believe that the evidence is lacking to consider these animals as reservoirs. They found that in 48% of cases, isolation of thepathogen of the virus bat hadn’t even been done. Furthermore, the simple isolation of a virus would not be enough to consider an animal as a reservoir because there would also have to be an established route of transmission.

An effective immune system and little zoonotic danger for humans »

According to the study, bats have a highly efficient immune system that allows them to better deal with a variety of deadly viruses than other mammals. It’s been 60 million years since bats evolved to adapt to powered flight. Likewise, they face viruses that have evolved over millions of years and show a moderate response during inflammatory processes. Then they recover and remain immune by developing a high level ofantibodyoften without becoming a reservoir “, write the authors.

After immunity, their risk of relapse, to the point of becoming contagious, is weak. Dissemination of viral pathogens can only occur if bats harbor the same pathogenic virus for humans. However, many viruses carried by bats cannot infect humans without first undergoing a natural process of evolution, which means that bats carry the ancestral viruses and not the human pathogen. . »

It cannot be ruled out that bats may have been carriers of an ancestral virus which, at some point, could have mutated into a pathogenic agent for humans. However, Israeli researchers conclude that with the exception of a few viruses, bats pose little danger zoonotic for the man.

Instead, they focus on showing that the unique antiviral immunological abilities of bats need to be better studied in order to fight our own diseases. These animals also play an important role in the extermination of insectsthe replanting of deforested areas and the pollination of a number of crops.

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