SARS, MERS, Ebola, Marburg, rabies. The new COVID-19 coronavirus may well be added to this list of viruses that originate from the bat in the coming weeks.
But why is this small mammal linked to the emergence of epidemics in humans?
US biologists at the University of California at Berkeley explain that this role as a virus incubator is due in part to the highly efficient immune systems of many bat species, whose defenses cause virus strains to adapt.
Viral infection in bats results in a rapid reaction of their immune system, which clears the virus, which ultimately protects it from a high viral load.
Result: when these strains move to another species, and ultimately to humans, they prove to be very infectious since the immune system of the new host is not as efficient as that of the bat. A reality that results in a high mortality rate.
Landmarks
If they are commonly called bats, these placental mammals are officially called bats (Chiroptera in Latin).
There are 1400 species of bats;
Among mammals, only rodents (Rodentia) have more species, with around 1700.
Bats everywhere
From the emergence of hemorrhagic fevers in the second half of the 20th century to the more recent emergence of new coronaviruses, the bat therefore seems to be the natural reservoir of many fatal viral epidemics.
Not surprisingly, in terms of the number of species, bats are the most important source of virus among mammals.
Bats have colonized almost every corner of the world except the polar regions and some isolated oceanic islands. They have very few natural predators, and live particularly long in relation to their size; some bats can live up to 40 years.
For all these reasons, it is not surprising, according to virologists, that many viral epidemics have their origins in bats.
“Not only do some bats have a strong antiviral response, but they also balance it with a good anti-inflammatory response.”
“Our immune system would generate widespread inflammation if it tried this same antiviral strategy. Bats seem to be the only ones who can avoid the threat of immunopathology,” says Brook.
Everywhere men
Another equally important factor that promotes the spread of viruses carried by bats and other wild animals is the expansion of human activities.
Significant destruction of the natural habitat of bats has been observed in recent decades. This reality puts them more in direct or indirect contact with humans and other animals.
Thus, their saliva, urine and excrement infected with viruses come into contact with species they did not meet before, and infect them at the same time.
There is also human consumption of wild animals which is pointed out.
MediaCongo
Ouest-France / MCP, via mediacongo.net
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