‘Deforestation, exploitation of wildlife leads to pandemics like Covid-19’: Epidemiologist
New research has confirmed that Sars-Cov-2 is very closely genetically related to coronaviruses from bat populations, and specifically rhinolophus bats, and pangolins may have been intermediate hosts in transmission to humans.
Such pandemics will become more likely and spill-over risks of dangerous viruses are increasing even as Covid-19 outbreak is bringing the world to a grinding halt.
Dr Pranav Pandit, a veterinary epidemiologist at One Health Institute, University of California Davis, said there is scientific evidence linking deforestation, rapid urbanisation, climate change with pandemics like Covid-19, which offer clues to how pandemics can be prevented.
Excerpts from an email interview:
Q. Is there scientific evidence about the natural origin of Sars-Cov-2?
A. Epidemiologically speaking, the latest evidence including a paper in Nature published on May 7 points towards a hypothesis that bats could harbour the phylogenetic ancestor virus of Sars-Cov-2. The most likely candidate is “bat coronavirus RaTG13” and Malayan Pangolins could be intermediate hosts. The earlier relationship of Sars-Cov-2 with “bat coronavirus RaTG13” was raised by the analysis conducted by other papers also.
Q. An estimated 60% of emerging human pathogens are zoonotic. Why has the threat of zoonotic diseases increased?
A. There is surely an increase in emerging viruses from animals. Just over the last five years, the world has seen great outbreaks of emerging zoonotic viruses including the Zika virus, Ebola virus, and now Sars-Cov-2. Overall, this is attributed to anthropogenic pressures that we exert on environmental systems, including cOur recent study shows that exploitation wildlife populations and degradation of habitats are one of the important ecological divers behind the emergence of viruses from wildlife to humans. https://royalsocietypublishing.org/doi/10.1098/rspb.2019.2736
These rapid anthropogenic changes are animal-human interfaces where humans frequently get in contact with wild animals allowing viruses to evolve and jump into humans leading to the emergence of a new virus. Some of our earlier work has similar interpretations for a group of emerging viruses called flaviviruses (zika virus, yellow fever virus, dengue virus). https://www.nature.com/articles/s41467-018-07896-2
Q. Did scientists see a pandemic of this scale coming?
A. Because the world is more interconnected than ever through travel and trade, it is likely that we will see pandemics at an increasing rate. We hope we can shift thinking from pandemic response to pandemic prevention. Disease emergence that occurs anywhere can affect us all and we need to all understand the impact we are having when we interact with wildlife, realise that disease emergence is an environmental issue, and find more sustainable ways to co-exist.
Q. What is the link between deforestation and zoonoses?
A. We alter the landscape through deforestation, conversion of land for growing crops or raising livestock, or building up communities, and this, in turn, alters the natural distribution of wildlife and increases the frequency and intensity of contact between humans and wildlife – creating the perfect conditions for virus spillover. Wildlife also shift their distributions to accommodate anthropogenic activities and modification of the natural landscape. This has hastened disease emergence from wildlife, which puts us at risk of pandemics because we are all globally connected through travel and trade.
Q. Could certain indigenous hunting communities have antibodies to these viruses?
A. Certainly, antibodies against some zoonotic viruses have been detected in certain tribal communities without any known detected outbreak of disease. This only means that those communities have been only exposed to those or similar viruses since many times serological response and tests are not very specific to a single virus. An example of a study in India is the following https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0007733. Studies like these show human-animal interactions lead to exposure of animal viruses to humans.