Last summer, the idea that a virus hitherto confined to the bat could paralyze the entire planet seemed implausible. Finally … not for scientists. “The World Health Organization (WHO) like the World Organization for Animal Health (OIE) lists around twenty zoonoses (Editor’s note: animal diseases) to watch closely ”, recalls Julien Capelle, specialist in rodent and bat diseases.
This ecologist from the Center for International Cooperation in Agronomic Research (CIRAD) participates in ZooCov, a brand new research program funded in emergency since the beginning of the coronavirus crisis to better understand the links between animal and human health. 60% of infectious diseases affecting humans come from animals. This is the case with measles, of bovine origin, whooping cough, which comes from pork, or the flu, transported, among others, by ducks. AIDS is also a zoonosis, just like Ebola or SARS.
In question, our lifestyles
In the case of Covid-19, the researchers have established with certainty that the disease comes from a bat. But the virus hosted by these small nocturnal animals is not equipped to attack humans, it had to mutate through another species, the pangolin it seems. This funny little mammal, fond of ants and covered with scales, hardly resembles us, however. “At the morphological level, it’s true,” agrees Julien Cappelle. But at the cellular level, its membrane has a similar protein composition. “
VIDEO. Pangolin may have transmitted coronavirus to humans
Viruses have always passed from animals to humans, nothing new, then? “Because of our modern lifestyles, contacts between humans and animals have been multiplied, which has led to accelerating human transmission”, points Coralie Martin, specialist at the National Museum of Natural History (MNHN) and author of a podcast on zoonoses.
Population density, globalization, destruction of biodiversity, trafficking in wildlife and intensive farming are the ingredients of an explosive cocktail. We speak of a “disease reactor”. “Take deforestation, it is not a cause of these pandemics but an aggravating factor,” says Coralie Martin. By destroying forests, to grow oil palms, soybeans, or to expand cities, we fragment natural environments and weaken the fauna that live there.
These virus reservoirs are now at the gates of villages. This problem is not confined to tropical forests. “In the northeast of the United States, deforestation has severely impacted predators of white-footed mice. However, this rodent contributes to the spread of Lyme disease, ”reports the ecologist. “There is an urgent need to adopt another relationship with the animal. This is not an ecological discourse but a scientific observation, “she insists.
Should we fear a “big one”?
With our lifestyles, we put ourselves in double jeopardy: first we “create” the crucibles where new diseases are made; then we destroy the balances that protect us from it. Should we therefore expect an explosion of global epidemics? Should we fear a “big one”, a highly contagious and lethal virus, like the black plague? “Impossible to predict,” replied Julien Cappelle. The whole problem with these emerging diseases is the high level of uncertainty. There are millions of viruses in animal reservoirs, but most will never be transmitted to humans. “
Scientists in any case warn against false good solutions. Thus those who would be tempted to eradicate the bat or the pangolin, because they served as a reservoir for the Covid would risk “upsetting fragile equilibria and applying a remedy worse than the disease by removing a link elsewhere useful ”, points out Coralie Martin. Case study, in India in 2004, 95% of the vultures had been decimated either voluntarily by poachers, or because of a treatment used on farmed oxen which then poisoned the scavengers. In the absence of a vulture, stray dogs had taken over the vacant position and favored an epidemic of rabies killing 48,000 people.
“Brutally closing the markets for wild animals (Editor’s note: suspected of causing the coronavirus pandemic) would be counterproductive, says Julien Cappelle. Bushmeat will not disappear with a snap of the fingers. In some countries it is vital, in others it is deeply rooted in habits. The whole industry would go underground and be much more difficult to trace. With his teams, he prefers to map the sector, its actors, inform them, help them to be tested… So many actions which make it possible to detect viruses before they reach the planet.
Four media are involved. Le Parisien, France Culture, Konbini and Usbek Rica – four different media in their approach and readership – join forces around the theme of the environment. Each month, we deal with a subject decided jointly. Textile pollution, problem of illegal dumping, recovery of electronic waste… Find all of our articles and multimedia content on social networks with the hashtag #SauverLePresent.