Scientists link outbreaks such as Covid-19 to biodiversity loss

ByJayashree Nandi
Mar 15, 2020 06:40 PM IST

New Delhi: The rise in zoonotic diseases like the coronavirus disease, or Covid 19 is linked to the loss of biodiversity and forests, public health experts and scientists have said. Zoonotic diseases are those that spread from animals to humans.

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There is a consensus among scientists that a rise in zoonotic diseases--Nipah, Ebola, Avian Influenza, Zika, Coronavirus to name a few in recent decades – is driven by biodiversity loss and climate change.

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In a press briefing held in New York by the Global Alliance of Indigenous Peoples on Friday, indigenous leaders said the Covid 19 outbreak was a result of loss of native forests and habitat.

“The coronavirus is now telling the world what we have been saying for thousands of years—that if we do not help protect biodiversity and nature, then we will face this and worse future threats,” said Levi Sucre Romero, a BriBri indigenous person from Costa Rica who is the Coordinator of the Mesoamerican Alliance of Peoples and Forests.

Scientific studies have already flagged this link. The Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (Similar to Intergovernmental Panel on Climate Change) in their report last year said that zoonotic diseases are significant threats to human health, with vector-borne diseases accounting for approximately 17 % of all infectious diseases and causing an estimated 700,000 deaths globally per year.

“Emerging infectious diseases in wildlife, domestic animals, plants or people can be exacerbated by human activities such as land clearing and habitat fragmentation,” the report said. It also highlighted that around 25% of species in the animal and plant groups were under threat, suggesting that around one million species are already confronting extinction.

The World Health Organization has said there is now evidence of the link between the 2019-nCoV and other similar known coronaviruses (CoV) circulating in bats, and more specifically those of the Rhinolophus bat sub-species.

But the route of transmission to humans is still unclear. The most likely hypothesis is that an intermediary host animal played a role in the transmission of this disease.

According to a 2010 study in the journal Emerging Infectious Diseases, about 60% of emerging human pathogens are zoonotic. Of these pathogens, over 71% have wildlife origins.

“There is no doubt that zoonotic diseases are on the rise. One of the reasons for their rise, among many others, is that animals are coming in contact with human habitation. Chikungunya, for example, also came through an intermediate host. More interactions are happening between animals and humans, which may not have been the case earlier. Some emerging zoonotic diseases include Bacterial Anthrax, Brucella, Leptospira, Salmonella, Kyasunar forest disease, Avian influenza, Crimean Congo Hemorrhagic fever, Nipah, Corona among others,” said Dr Shobha Broor, former head of department of microbiology at the All India Institute of Medical Sciences.

“Now we know that COVID 19 may not have come from snakes. Even from evolutionary perspective, pangolins and bats are more closely related to us than snakes. There is a definite link of forest loss, climate change and these zoonotic diseases. In Karnataka for the past few years, there are reports of the Kyasanur forest disease particularly from Shimoga. There is agreement that it has got to do with habitat loss. Also, cattle enter forest areas transferring infections to wildlife and vice versa,” said Kartik Sunagar, assistant professor, Evolutionary Venomics Lab at Centre for Ecological Sciences, Indian Institute of Science.

“Many mammals, like bats and rodents, harbour virsues and bacteria that can spillover from wildlife populations into humans. Sometimes these spillover events can cause outbreaks, like the one we are experiencing now. Meta-analyses of spillover events across the world suggest that they are more likely to occur when the number of mammal species in an area is high, such as in tropical, biodiverse environments. But other important drivers of spillover are land conversion (e.g. forest clearing for agriculture or developmental activities) and human population density. In parts of India, all three of these are high: we have high biodiversity, high land conversion and high human population density. We must better understand the dynamics of spillover in such situations,” said Uma Ramakrishnan, Associate Professor, Senior Fellow, Wellcome Trust, National Centre for Biological Sciences.

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