Our appetite for animals poses big disease risks

In 2017, after years spent looking into the SARS epidemic that tore through China a decade-and-a-half earlier, a team of researchers thought they may have discovered the origins of the disease: a cave in Yunnan province crowded with different species of horseshoe bats. The researchers wrote that they had discovered in the bats the genomes of several different coronaviruses, and in these genetic codes, the “building blocks” of the virus that had infected more than 8,000 people years earlier, killing 774 of them.

There was uncertainty about how SARS had travelled 1,000 kilometres from the Yunnan cave to Guangdong, where it was first reported in late 2002. But one thing is clear: Bat coronaviruses can infect humans. Some villagers around Yunnan bat caves had antibodies to the bat diseases. In the case of SARS, researchers think the civet, a cat-like wild animal that’s a delicacy in some parts of China, played the role of intermediary host, spreading the bat virus to humans.

The wildlife trade may also have played a part in spreading the new coronavirus, formally called COVID-19, to people in Wuhan, China, where the first cases were reported. Given the alarming headlines about the coronavirus outbreak and the consumption of wildlife, the tradition of so- called wet markets, where wild animals are sold, now faces harsh scrutiny. But eating wildlife is not the only way diseases can spread from animals to people, nor are respiratory viruses like the new coronavirus the only diseases that we should be concerned about when it comes to eating meat. The world’s system of animal husbandry, food production, and food distribution has certainly been linked before to deadly microbes, such as strains of E.coli.

Selling and eating wild animals, disrupting ecosystems, and destroying forests all contribute to the risks of novel deadly microbes spreading into human populations. Just as worrisome is the impact that raising hundreds or thousands of domesticated animals in densely packed quarters has on the worsening problem of drug-resistant microbes. While the new coronavirus in China has killed more than 2,300 people, about 35,000 people in the United States die each year after developing drug-resistant infections.

Antimicrobial resistance is a growing problem in China, as well. The country’s appetite for meat has increased as it becomes more affluent, as is the case in other developing countries. Meat provides essential micronutrients and is an important part of many cuisines. People in the United States and other rich countries consume much more meat per capita than people living in the developing world. Indeed, the affluent are in no moral position to make demands about what others can or cannot eat.

Does the consumption of wild animals (aka bushmeat) pose special risks with regard to public health? Bushmeat consumption is common in African and Asian countries, especially in China. It’s an important source of protein and provides food security for poor people living in rural areas. Outbreaks of diseases like Ebola, however, have been linked to eating it. (While domesticated animals harbour microbes that can cause foodborne illnesses such as Salmonella, Campylobacter, and E. coli, wild animals harbour deadly microbes, including novel viruses such as influenza, Ebola, and Nipah, that can spill over into domesticated animals and humans.)

China may now be clamping down on the wet markets that sell wild animals, something that has been tried on a temporary basis before. The emergence of SARS in 2003 prompted the government to ban the wet markets, but that effort failed, and led to a rise in black markets. In the current crisis, China has once again banned wild animal sales, at least until the epidemic is over. But there are signs that the government may adopt more stringent policies going forward.

Meat production has grown 68 percent in Asia over the last 20 years, and the continent is home to a majority of the world’s chicken and pigs. Asian countries like India and China are working to improve poor sanitation and hygiene, but both of them also use massive amounts of antibiotics and have very high rates of antimicrobial resistance. China’s decisions on wildlife in wet markets won’t change that.

Consuming less meat (and raising fewer animals for food) could ease the problem. (Interestingly, India, which has, by far, the highest percentage of vegetarians in its population, at 38 percent, hasn’t had the same coronavirus spillover events like China, despite also having wet markets.) China’s decision on how to handle the wildlife trade could affect the likelihood of another outbreak of something like the coronavirus. How the world handles the production and distribution of domesticated animals, however, may be just as consequential a decision.

Antimicrobial resistance doesn’t receive the same intense level of media coverage as the new coronavirus. Nevertheless, the global demand for animal proteins, whether from domesticated or wild animals, is growing and becoming unsustainable. Promoting meat alternatives or vegetarian diets might be a step in the right direction.

Courtesy the bulletin.org, the website of the Bulletin of the Atomic Scientists