COVID-19: Possible link between virus, intensive pig farming, says study

SARS-CoV-2 may have transmitted from infected pigs to a farm worker, from pig meat to the human food chain or from pig faeces into the environment, contaminating drinking water

By Rajeshwari Sinha
Published: Monday 01 June 2020

There may be a link between the emergence of the novel coronavirus (SARS-CoV-2) that causes the COVID-19 disease, intensive pig farming and the agro-industrial complex, according to a paper published in May, 2020 on ResearchGate, a research network for scientists across the world.

Researchers from the University of Nottingham, UK and University of Sao Paulo, Brazil proposed a triangular hypothesis: They said three species — bats, pigs and humans — have come close enough to promote the evolution of an infectious virus, possibly because of the industrialisation of agriculture.

The origin of SARS-CoV-2 in China may be linked to swine factories in the country’s Hubei province, according to the authors of the paper.

The province — the capital of which is Wuhan, where the first reported COVID-19 infection was discovered — is known for the factory farming of pigs for pork meat.

Bats — which have emerged from their receding natural habitat because of Wuhan’s growth — may have found new shelter in pork factories, where they are safe from predators and get access to soy-based diets meant for pigs.

As they adapt to this new habitat, there is a possibility of them spreading viruses to the pigs, until a virulent new species emerged and circulated among pigs for many years before jumping to humans.

The virus may have transmitted from infected pigs to a farm worker, from pig meat to the human food chain or from pig faeces into the environment, contaminating drinking water, according to the paper.

Pig farming in Brazil

Researchers also mapped pig farming factories in Brazil’s Santa Catarina state, that reported COVID-19 infections.

There was an overlap between municipalities in Santa Catarina that had a large number of pigs per farm or pigs per municipality and those that had a greater number of people infected with COVID-19, according to the paper.

Brazil is the world’s fourth-largest exporter of pork. Santa Catarina is the state that produces most of this pork and is responsible for more than 25 per cent of the total production in Brazil.

About 70 per cent of pigs reared for pork meat are raised using an intensive farming approach where they are confined to small spaces and administered chemicals like hormones, antibiotics etc.

Such farming conditions make the animals ‘immune-depressed’ and more susceptible to the spread of infectious diseases, according to the authors.

There is also an increase in deforestation in Brazil to cultivate soy and corn monocultures that are again used as feed for pigs.

Such farming practices also lead to severe environmental contamination due to improper disposal of pig waste.

The emergence of SARS-CoV-2 is believed in some quarter to have emerged from bats — likely natural reservoir hosts for the virus — and passed onto humans via pangolins.

Though a few initial studies indicated the virus replicated poorly in pigs, there was also speculation that pigs may be possible vectors for the SARS-CoV-2 in humans.

The present hypothesis adds to the understanding that intensively-raised pigs may have been a vessel for the circulation of the virus long before its transmission to humans.

As more forest cover is destroyed to grow animal feed, bats are being brought closer to human habitats and so are the viruses borne by them.

This triangular relationship between bats, pigs and humans may add to the existing risks of the present pandemic and pose a future threat, according to the authors.

They propose there is a need for more research to avoid the emergence of new viruses and to implement sustainable farming practices as well.

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