Emerging Diseases
5 minute read
Back in March we explored the link between deforestation and outbreaks of infectious diseases. A big thank you to reader Geoff who sent me this fascinating article written by veteran environmental journalist John Vidal, which explores how other aspects of humans relationships with animals and how our manipulation of nature puts us at risk of yet more devastating pandemic events. Beyond deforestation, Vidal argues that there are four further ways potentially catastrophic diseases can spillover from wildlife into human populations.
Intensive Farming – Pathogens lurk in domesticated animals just as they do in wild ones. Populations of not particularly genetically diverse livestock (the result of artificial selection) kept at close quarters to each other and to humans create the perfect disease reservoir and zoonotic infection mechanism. Further to this, estimates suggest that more than 170 wild species (like snakes, civet cats, porcupines and pangolins) are now being farmed. The 2009-10 H1N1 “Swine Flu” pandemic which is estimated to have killed somewhere between 151,000 and 575,000 people in a single year is thought to have come from intensive pig farming. H5N1 (a.k.a. Bird Flu), MERS, salmonella, smallpox and measles are all also thought to have originated in domesticated animals.
Urbanisation – fast growing cities, especially in the developing world cram people and animals together often in unsanitary conditions, this creates yet more opportunities for diseases to spillover into human populations. The density at which people often live combined with the interconnectedness of cities (e.g. water, sewage and transport systems) allow infectious diseases to spread like wildfire. It is thought that this is how SARS first took hold in Hong Kong in 2002.
Exotic Pets – this one surprised me. Pet ownership is at an all-time high and increasingly these are not just cats and dogs. Captive reptiles, birds and rodents have been known to spread salmonella, meningitis, monkeypox (from prairie dogs, not monkeys), Chagas disease, ringworm and lyssaviruses (which cause rabies).
Human Error – despite Trump and Pompeo’s best efforts, this is not currently believed to be the source of COVID, but accidents in research labs do happen. Smallpox and Foot and Mouth disease are recent UK examples while CDC labs in the US have inadvertently let Ebola and bird flu escape.
So besides goal 3, Good Health and Wellbeing, what does all have to do with sustainability? The answer, food. So much of our manipulation of nature that is causing the spillover of novel diseases (especially the deforestation and intensive farming) is driven by the need to feed our ever-growing population. So what should be done? Ban the often unhygienic wet markets where wildlife is traded – like the one in Wuhan thought to be COVID ground zero? Or perhaps just the bushmeat trade? Absolutely not. Hundreds of millions of people rely on such (formal and informal) markets for their food and the bushmeat they buy there is their primary source of protein – particularly in sub-Saharan Africa, Latin America and South and East Asia. A knee-jerk reaction that outlaws these markets overnight would jeopardise the food security of a significant portion of the world's population. The additional agriculture required to replace the nutrition sourced from bushmeat with farmed food would increase land clearance, carbon emissions and water consumption; and for the reasons just discussed may not even reduce the number of disease outbreaks.
It’s also important to note that the vast majority of the wild species consumed as bushmeat are neither endangered nor dangerous (from a disease transmission perspective). Local authorities and national governments need to monitor the activities and hygiene of food markets far more closely, especially in the developing world, rather than prohibit them altogether. We must also be very careful not to blame the developing world for disease outbreaks. While it is true they tend to suffer from them disproportionally, we must remember that the deforestation and intense agriculture that has caused so many of these problems is largely driven by the food demand of rich countries.
More broadly, this crisis and its origins demonstrate exactly why we must approach human health, animal health and ecosystem health as one. The world's biosecurity depends on it. There will be far more to discuss on this topic in the months to come.