From a March 30, 2020 article in Grain:
Another recently published study identifies the most likely intermediate animal hosts for SARS-CoV-2, based on their presence in Wuhan and their having a human-like ACE2 that enables the binding of SARS-CoV-2. These are the animals the study identified: civets, pigs, pangolins, cats, cows, buffalos, goats, sheep and pigeons8.
Many of the animals on this list are industrially farmed in China, even wild animals like civets and pangolins are intensively farmed for their use in Chinese medicines. Suspicions that wild animal farms may have been behind the Covid-19 outbreak have already led the Chinese government to shut down 20,000 wild animal farms across the country9.
But hardly any attention has been given to some other animals on this list, which more clearly meet the “high population density” criteria. Pigs would be one obvious candidate from this list, for several reasons.
For one, pigs and humans have very similar immune systems, making it easy for viruses to cross between the two species, as happened with the Nipah virus outbreak in Malaysia in 199810. Indeed, just three years before the Covid-19 outbreak began, tens of thousands of pigs in four factory farms in Qingyuan county in Guangdong, less than 100 km from the site where the SARS outbreak originated in 2003, died from an outbreak of a new, lethal coronavirus strain (SADS) that turned out to be 98 percent identical to a coronavirus found in horseshoe bats in a nearby cave11 . Luckily transmission to humans did not occur, but subsequent laboratory tests demonstrated that such transmission could have been possible12.
Many of the animals on this list are industrially farmed in China, even wild animals like civets and pangolins are intensively farmed for their use in Chinese medicines. Suspicions that wild animal farms may have been behind the Covid-19 outbreak have already led the Chinese government to shut down 20,000 wild animal farms across the country9.
But hardly any attention has been given to some other animals on this list, which more clearly meet the “high population density” criteria. Pigs would be one obvious candidate from this list, for several reasons.
For one, pigs and humans have very similar immune systems, making it easy for viruses to cross between the two species, as happened with the Nipah virus outbreak in Malaysia in 199810. Indeed, just three years before the Covid-19 outbreak began, tens of thousands of pigs in four factory farms in Qingyuan county in Guangdong, less than 100 km from the site where the SARS outbreak originated in 2003, died from an outbreak of a new, lethal coronavirus strain (SADS) that turned out to be 98 percent identical to a coronavirus found in horseshoe bats in a nearby cave11 . Luckily transmission to humans did not occur, but subsequent laboratory tests demonstrated that such transmission could have been possible12.
Hubei Province, where Wuhan is located, is one of the top five largest producers of pigs in China. Over the past decade, small pig farms in the province have been replaced by large factory farms and medium-sized contract operations, where hundreds or thousands of genetically-uniform pigs are confined in high density barns. These industrial farms are the ideal breeding grounds for the evolution of new pathogens13.
Hubei’s factory pig farms are still reeling from a massive outbreak of African swine fever that struck the province and other parts of China just over a year ago, wiping out up to half of the national herd14. In these conditions, it is entirely possible that an outbreak of a new coronavirus among pigs in the province could go unnoticed.
Source:
https://www.grain.org/en/article/6437-new-research-suggests-industrial-livestock-not-wet-markets-might-be-origin-of-covid-19#sdfootnote14sym
