Viruses and vicious circles
In the last weeks, the images of the slaughter of minks in Danish livestock have become viral. 15-17 million of specimens, coming from intensive farming for the production of fur, were killed, “guilty” of contracting Covid-19 (from human beings), which has then mutated into a new form that is immune to the vaccines now under experimentation.
According to the results from preliminary investigations, the virus inside minks is likely to transform into a new strain, and therefore it represents a real danger for public health. Not even the protests of fur manufacturers led to anything: the Danish prime minister Matte Frederiksen was forced to act drastically to safeguard the whole world from a new threat.
As one can see from the website of the World Organization For Animal Health, infections of minks in intensive farming had been already signalled in April, and were caused by the animals’ exposure to human beings who then tested positive to the virus. Among the animals that can contract the coronavirus Sars-Cov-2, mustelids are the most susceptible, according to studies. Ferrets and minks, but also martens, badgers, weasels, and ermines could become a source of infection in which the virus can mutate to adapt itself better to the new guest – in this case, back to human beings.
Scientists group diseases that derive from these processes under the name of zoonosis.
The word identifies every infectious disease that can be transmitted from animals to human beings and vice versa. They can be caused by viruses, bacteria, parasites, or other pathogens, but they represent a serious risk for global health anyways.
According to the National Institutes of Health, almost the 16% of global deaths can be attributed to infectious diseases, and zoonoses represent the 60% of known infectious diseases and the 75% of emerging infectious diseases.
Zoonoses can be transmitted in various ways, among them insect stings, touching sick animals, and through the consumption of undercooked meat, non-pasteurised milk, or contaminated water. Some zoonotic diseases are relatively benign, but many of them, such as Lyme disease, are quite damaging. Others, such as the coronavirus that causes COVID-19, can even be lethal.
For instance, the main theory on the origin of the new Coronavirus pandemic claims that a spillover event occurred, through which the virus came into contact with a new host population, human beings, in a wet market in Wuhan, China. Spillover infections usually occur after a prolonged contact between man and the animal with the original pathogen; the more prolonged and close-range the animal-man exposure, the more statistically probable that a virus casually mutates into a new strain that can infect human beings.
Zoonosis is a natural phenomenon, and the human species has been living with it for millennia. The problem is that the modern world facilitates the transmission of infectious diseases much more than in the past. In a few decades, epidemics and pandemics such as Ebola, SARS, Zika, HIV/AIDS, West Nile fever, Covid-19 have followed one another. All of them have one thing in common: they are transmitted from animals to humans. And, in the future, things might even get worse.
“There are many reasons why zoonotic diseases are becoming more prevalent. Habitat loss, agriculture intensification and wildlife exploitation – including its illegal trade – are reducing barriers between the human and animal world. That is making it easier for germs to pass from other species to us”. With these words António Guterres, UN Secretary-General, presented his last report on Covid-19 “Preventing the next pandemic. Zoonotic diseases and how to break the chain of transmission” of the United Nations Environment Programme (UNEP).
The central theme of the document is men’s responsibility in the spread of these infectious diseases. Obviously, not all of them become pandemics or epidemics.
They usually represent endemic problems in the poorest communities, with inadequate basic hygiene measures, poor access to water and sewage or waste disposal. Since they do not become global phenomena, they are often forgotten (or neglected), but their sanitary toll is still high. In addition, it is a relatively short step from endemic problems to pandemics.
It is widely known that man has failed the ultimate goal of living in harmony with nature, and that humans are responsible for the outbreak and diffusion of these diseases and their “potentialities”. Already some fifteen years ago, at the end of the conference of health experts on the issue “One World, One Health”, a series of indications for politicians and rulers were formulated to prevent future pandemics. In 2012, the theme drew the attention of the global community of non-experts thanks to David Quammen’s best-seller “Spillover”. Quammen expresses the core concept very well in his book: these clusters of diseases aren’t something bad that happens to us, but rather the unwanted result of what we are doing; “Even though some of the man-made factors seem unavoidable, we have to understand that others can be controlled”. Of the latter, the UNEP report identifies seven.
The first can be identified in the growing demand for animal proteins, especially in developing countries. The First World did not undergo significant changes from this point of view in the last four decades, while there has been a marked and quick increase in South-East Asia and Sub-Saharan Africa. In addition, the population grew significantly, which in turn caused a substantial growth in meat (+260%), dairy (+90%), and egg production (+340%) in the last 50 years.
This has led to the second factor, that is the unsustainable intensification of farming. The growing demand for food of animal origin stimulates the industrialisation of animal production, which in practice translates to a great number of genetically similar animals that are herded one next to the other in poor condition. In this way, animals become much more vulnerable to infections.
In addition, wild animals are increasingly exploited. The hunting, commerce, and consumption of their meat, the use of some of their body parts for decorative, medicinal, commercial purposes: practices that increase the close contact between these species and man, with a higher risk of zoonosis.
The uncontrolled use of natural resources follows next. Wild urbanisation and the consequent fragmentation of habitats create new and diversified contacts between wild fauna, cattle, and people.
Another critical factor is represented by travels and transport, not only of animals, but of people as well. Diseases can now move all over the world faster than their incubation period – and the growing number of human travels and commercial exchanges does not help either.
Last, changes in the food industry and climate close the circle. Food supply chains are extending and diversifying, often without any regulation and information on the origin and preservation of food, especially in low and medium-income countries. This tendency – directly caused by the above-mentioned factors – creates further opportunities for the transmission of diseases. And so does the climate crisis: several zoonoses are sensitive to climate and some of them will thrive in a hotter, damper world, more susceptible to environmental disasters, as the ones predicted in future scenarios.
Some factors are almost unavoidable, others are under our control. Anyway, all of them cause the loss of biodiversity and habitat, which basically facilitates the outbreak and diffusion of zoonoses. This is also what Inger Andersen declares, the UNEP Executive Director: “The science is clear that if we keep exploiting wildlife and destroying our ecosystems, then we can expect to see a steady stream of these diseases jumping from animals to humans in the years ahead”.
To avoid it, we can (or rather, we have) to preserve habitats in their integrity, promote sustainable agriculture, reinforce the standards of food security. But also monitor and regulate food markets, do research, restrain the illegal commerce of wildlife, and change our food choices. We are talking of the One Health approach, supported by the report and the Who, defined as the “collaborative and multidisciplinary effort to attain optimal health for people, domestic animals, and our environment”. An approach based on the idea that human health depends on the health of the planet and other species in a virtuous circle on a global scale, because viruses do not need passports.