Almost a year ago a devastating report was published that warned that there are a million species in danger of extinction in the world and the rates of disappearance are accelerating at an unprecedented rate as a result of human activities. Now a study published in the journal Proceedings of the Royal Society B. highlights the relationship between these processes and the spread of infectious diseases such as COVID-19.
As the results reveal, the mechanisms that lead to declining populations of wild species also allow greater transmission of viruses from animals to humans, a process known as zoonosis. “The spread of viruses from animals is a direct result of our actions on wildlife and their habitat,” explains lead author Christine Kreuder Johnson of the University of Davis California (USA). “As a consequence, animals are sharing their viruses with us, and these actions, simultaneously, threaten the survival of the species and on the other hand increase the risk of contagion. The disaster in which we are immersed right now has been caused by an unfortunate convergence of many factors, among which includes this ”.
To arrive at these results, the scientists analyzed information from the 142 viruses in which zoonoses are known to have occurred, as well as from all the species involved in the process as potential intermediate hosts . Using information from the International Union for Conservation of Nature’s Red List of Threatened Species, they examined species abundance patterns, extinction risks, and the underlying causes of their declining populations.
Three groups of species involved in zoonosis processes can be established: firstly, domestic animals, which due to their proximity to humans are the vector agents for the largest number of viruses. Second would be those species well adapted to the most humanized environments, such as some rodents and bats, and which are also very common vectors. And finally, threatened species: those that are endangered due to trade, hunting, habitat degradation and excessive urbanization are twice as likely to be vectors of zoonotic viruses than those that are threatened for other reasons. . The conclusion is logical, since they are species that would also have a closer contact with man.
Biodiversity protects us from emerging diseases
In recent years, it has already been shown that the loss of biodiversity modifies and increases the transmission of diseases through various mechanisms that generally have to do with modifying the abundances or behaviors of hosts and vectors. For example, in the case of Lyme disease, transmitted by ticks, it is thought that the increase in its incidence in the United States would have to do with the decrease of some populations of birds that under normal conditions served as a natural reservoir for the bacteria contained the transmission. By simultaneously increasing the populations of rodents, which are also transmitters, the jump to the human species would have been favored.
We need nature to protect our health
Fernando Valladares, researcher at the National Museum of Natural Science (CSIC), also warns of the consequences of environmental degradation in an inspiring video published on his You Tube channel The health of humanity . “The blame for this crisis is not bats or pangolins, but our new global habits in the midst of a simplified and impoverished nature that does not fulfill its protective effect , now that we need it so much,” explains the scientist. “We live with our backs to nature, but our health depends on it much more than we think. More viruses will come, as indicated by the World Health Organization, and some will be more lethal and dangerous than the coronavirus itself. There will be no health system that can contain them. Only a rich and functional nature, with adequate levels of biodiversity, will be able to cushion the impacts of future zoonoses on the health of humanity ”, he concludes.
Photo: Rhesus macaques in Kathmandu. Primates are among the animal taxa most likely to harbor viruses that could spread to humans. Rhesus macaques are highly adaptable to urban landscapes, making them more likely to transmit viruses to humans.
