Human beings are increasingly coming into contact with the wild. We gain ground from nature in many ways. We install new industries, power generation systems, use the wilderness as a form of tourism, even expand our cities and towns by reclaiming natural land for urbanization.
All of these activities increase our contact with the wild and wild species are inevitably forced to interact with us and our infrastructure. Having less territory of their own, they are forced to enter new environments occupied by humans. Wild species are hunted to use as pets, they are sold in markets for meat consumption, they are used as false remedies of the so-called traditional medicines, etc.
Among the most influential activities are the trade in wild animals and agricultural and livestock expansion. Invasive alien species are also often carriers of disease.
All this perverse dynamic negatively influences the health of ecosystems, and consequently, biodiversity, with obvious impacts in the form of extinction or displacement of species, alteration of processes of ecological succession, biogeochemical cycles, food webs, and in many other ecological processes.
But it also also causes humanity to come into more and more contact with wildlife, which favors the appearance of new diseases. Pathologies that wild animals suffer from naturally, that otherwise would not reach humans, but that due to increased contact end up infecting people, who in turn can infect others and become epidemic episodes. These diseases are called zoonoses .
The prediction of new zoonoses
The interrelationships between the biological, economic and social factors associated with the emergence of new zoonotic diseases are extraordinarily complex and of enormous dimensions, which makes it really difficult to predict, prevent and respond to the appearance of these new diseases. It is very complicated, therefore, to know which disease will be next, where the first contagion will occur, or how we can stop its progress. But just because it’s complicated doesn’t make it impossible.
The fact that, in 2007, a group of researchers from the state laboratory for infectious diseases at the University of Hong Kong already predicted that a pandemic disease caused by a coronavirus could spread from Southeast Asia is relevant. In fact, his warnings were as clear as they were ignored: “The presence of a large reservoir of viruses similar to SARS-CoV in horseshoe bats, together with the culture of eating exotic mammals in southern China, is a time bomb. . The possibility of re-emergence of SARS and other novel viruses (…) and therefore the need for preparation should not be ignored.”
With current human habits, a new epidemic —yes, yet another— of a zoonotic nature should surprise no one; It will only be a matter of time.
Some zoonoses of wild origin
Of the diseases that wild animals have transmitted to us, a long list has led to epidemic episodes and even pandemics. The most recent, the SARS-CoV-2 coronavirus , which, as far as we know, has its origin in wild animals, but it is not the only one.
Wild rodents can transmit leptospirosis —caused by bacteria of the Leptospira genus—, salmonellosis , Chagas disease —caused by the protist Trypanosoma cruzi— or hantavirus hemorrhagic fever . Rodents are also reservoirs of diseases such as the black plague —transmitted to humans by fleas—, typhus —transmitted by louses—, or Ebola.
Among birds, it is common to find certain types of flu such as H5N1 , which caused the bird flu epidemic that reached the threat of a pandemic in 2007 and 2008, or H9N2 .
Bats can transmit the Hendra virus to horses, which in turn can become vectors and infect humans. Along with weasels, they are reservoirs for SARS-CoV , the cause of the 2003 epidemic, and can also transmit rabies, something they have in common with raccoons, foxes, and wolves. The latter can also transmit diphyllobothriasis and hiraditosis .
Among camelids and cervids it is not uncommon to find cases of tuberculosis , anthrax or brucellosis , which can be transmitted to humans directly or indirectly through livestock. These diseases, however, can reduce their influence if there are viable natural predator populations in the ecosystem.
How do we avoid the next zoonosis?
The question is not so much how to avoid it, but how to delay it or how to mitigate its impact. Obviously, among the possible solutions is not to eliminate wildlife . We need to preserve biodiversity, if only for selfish reasons, to maintain our very existence. Increasing hunting of wildlife does not solve the problem; Unlike predators, human hunters tend to seek out large, strong prey, perpetuating the presence of disease.
The main way to prevent new zoonoses is to avoid contact with wild animals . Stop hunting them, stop trading them, prevent and eliminate biological invasions, and avoid contact in agricultural and livestock environments. Abandon those expansionist tendencies whose consequences are the breakdown of the landscape and the destabilization of the ecosystem. Implementing efficient and effective wildlife conservation policies will be the best way to prevent the next zoonotic disease epidemic.
References:
Azami-Conesa, I. et al. 2021. Invasive Species as Hosts of Zoonotic Infections: The Case of American Mink (Neovison vison) and Leishmania infantum. Microorganisms, 9(7), 1531. DOI: 10.3390/microorganisms9071531
Hair C, C. et al. 2008. Zoonoses with wild reservoirs: Threats to public health and the economy. Medical journal of Chile, 136(3), 385-393. DOI: 10.4067/S0034-98872008000300016
Cheng, V. C. C. et al. 2007. Severe Acute Respiratory Syndrome Coronavirus as an Agent of Emerging and Reemerging Infection. Clinical Microbiology Reviews, 20(4), 660-694. DOI: 10.1128/CMR.00023-07
Jones, B. A. et al. 2013. Zoonosis emergence linked to agricultural intensification and environmental change. Proceedings of the National Academy of Sciences, 110(21), 8399-8404. DOI: 10.1073/pnas.1208059110
Zaid, G. 2022. Chapter 3 – Zoonotic infections. En A. I. Qureshi et al. (Eds.), Coronavirus Disease (pp. 21-28). Academic Press. DOI: 10.1016/B978-0-12-824409-8.00008-4
