horseshoe bat – CHRISTIAN KOENIG / AFP
- The bat may well be the natural reservoir of the Covid-19 epidemic, analyzes a virologist.
- It could have transmitted the virus directly, or through an intermediary host, perhaps the pangolin.
- However, this should not tarnish the image of the bat, which is no more a carrier of viruses transmissible to humans than other animal species.
- In addition, cases of bat virus transmission to humans in France are almost impossible.
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Responsible, but not guilty … The bat is probably responsible for the Covid-19 epidemic, confirms the virologist of
Development Research Institute (IRD) Eric Leroy. While there are indeed many coronaviruses in bats, all animal species have been the cause of diseases and epidemics in humans in the same proportions, insists the scientist. And in France, there is no risk of transmitting this virus, or any other, from the bat to humans. Despite everything, the reputation of this small animal is likely to suffer in France, fear environmental associations. Yannig Bernard, from the chiroptères group in Aquitaine, wishes to reassure the population on this subject. The two specialists explain what you need to know about the bat.
What do we know to date about the role of the bat in the origin of the Covid-19 epidemic?
“There has not yet been a specific study on the mechanisms and modalities that led to the outbreak of the epidemic, nor on the transmission of the virus from its natural source to humans,” explains Eric Leroy, research director, virologist, specialist in
viral zoonoses to the
Development Research Institute (IRD). The only elements currently available are for comparison: the
Sars-CoV-2 is very close to Sars-CoV, responsible for the Sars epidemic in the early 2000s.
horseshoe bat, a kind of bat, being the animal reservoir of Sars-CoV, it is probably also the animal reservoir of Sars-CoV-2. To support this hypothesis, sequences were found in these bats, very similar to the sequences detected in humans at the start of the Covid-19 epidemic in December. To identify an animal reservoir of a disease, it is necessary to compare the viral sequences found in animals with those characterized in the first patients, because the virus evolves over time, and it will not be the same at the end of the pandemic, from what it was in the beginning. All these elements show that probably the bat is indeed the natural reservoir of the current virus. “
Did the bat transmit the virus directly to humans, or was there an intermediary?
In the case of Covid-19, “the bat is the reservoir host, that is to say, it permanently and asymptomatically harbors the virus,” says the virologist. “Several scenarios are envisaged, concerning transmission to humans. The first is direct transmission, which happens for example when these animals are eaten by local populations – and this is the case in Asia – when handling the killed animal. Another scenario reports indirect transmission, with the intervention of an intermediate host, which could be the pangolin – an animal widely consumed also in Asia – but not only. And another track would be a mix of the two, that is to say a virus which would be a genetic recombination between a pangolin virus, and a bat virus, and it is this mutant which could have infected the To be human. The field of possibilities is therefore still quite large. “
Why does the bat have such a bad reputation?
“It’s an animal that has always had a bad press, recognizes Yannig Bernard, volunteer of the Aquitaine bats group, because it lives at night, because there have been more or less baroque superstitions which have long endured like the myth of Dracula, which did not help, and which has long been said to be takes in the hair… However, we have the impression that there has been a change in recent years. The usefulness of the bat is further emphasized: it is an insectivore which plays an important role in the regulation of pests, such as
corn borer or the mosquito. Pipistrelles can eat several thousand mosquitoes in one night, but from the local mosquito I say, because the bat is not the good predator of the daytime tiger mosquito. He is also a consumer of vine predators, he eats
cluster worm. We have a big demand from wine growers who want to bring bats to their fields. “
Is the bat generally a preferred host for viruses?
“Not at all,” says Eric Leroy. A 2017 study, however, clearly showed massive and diverse presence of coronaviruses in bats. “Each animal species has its own viruses, and there are indeed many coronaviruses in bats, and only within the horseshoe bat genus,” confirms the virologist. But there are hundreds and hundreds of viruses. Other animal species harbor other types of viruses, and not all viruses are transmissible to humans. “The virologist insists:” It must be understood that all the great epidemics that have swept through populations for millennia, have always been diseases caused by pathogens, mostly from animals. Bats do have a certain number of physiological, biological and ecological characteristics which explain a great viral diversity hosted in them, but all animal species have been the cause of diseases and epidemics in humans in the same proportions. The idea which circulates, that the bats would be privileged reservoirs for human diseases, is therefore false. “
Do we find bat species of the horseshoe bat genus in France?
The horseshoe bat species are insectivorous and live in caves. “We find different species of horseshoe bat worldwide, including in France, even if some are specific to certain regions of the world”, explains Eric Leroy. The species suspected in the Covid-19 pandemic, Rhinolophus affinis, lives only in Asia. “There are a total of 34 species of bats in France, 26 of which have been identified in the territory of the former Aquitaine,” adds Yannig Bernard. There are three main groups of species in our region: those which are linked to the built space, which live in the roofs, the cellars, under the tiles, there are arboreal species, which live in the holes of trees, and we have species linked to underground environments, caves or quarries. Populations are still large in Aquitaine, especially in the Bordeaux agglomeration where there are many
common pipistrelles. “
Is there a danger of transmission of the bat to humans in our regions?
“No,” says the virologist, “in our country, the man has never been contaminated by a bat.” Some coronaviruses are hosted by bats living in our regions, but our way of life excludes direct physical contact. The risk of transmitting a virus from a bat to humans in France is obviously not zero, but it is infinitely low. In any case, not directly. “I have been studying bats for about twenty years, and I have never been aware of diseases transmitted to humans with this animal at home,” confirms Yannig Bernard. Even if the risk is almost zero, concerns about bats are likely to increase, and the reputation of the bat should still suffer. “It’s a fear, of course, admits Yannig Bernard. It comes up every time there is a problem with bats, it had already been the case during the first SARS epidemic. For the moment, a little worried people are calling us, and we are reassuring them. “
Is it possible to anticipate the transmission of the bat virus to humans?
“We are in the third coronavirus which passes in humans, now we know that it is a virus with a strong zoonotic potential, that is to say having a capacity to pass from animals to humans much more important than other viruses, explains Eric Leroy. So research must focus mainly on this viral family there. We have to characterize them as completely as possible, to highlight warning signals that tell us when a virus has evolved, and when it is close to being able to be transmitted to humans. Then, we can put in place strategies to prevent a possible event. “
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