Study of fur-farmed animals nets 125 viruses, including novel species and those with spillover potential

Mink in a cage on fur farm

TheAnimalDay.org / Flickr cc

Animals raised for their fur, such as raccoon dogs, fox, mink, and muskrats, may be an important reservoir and transmission hub for emerging viruses, including those at high risk for spillover into people, wild animals, and livestock, Chinese researchers reported yesterday in Nature.

Researchers from the Shanghai Institute of Infectious Disease and Biosecurity led the analysis of metagenomic mRNA in 697 intestinal, lung, and liver samples from 461 animals (412 from fur and/or livestock farms and 49 from wild settings) found dead, likely due to infectious diseases, across China. 

"The cross-species transmission of viruses from animals to humans drives infectious disease emergence, occasionally resulting in global pandemics," the study authors wrote. "As there is often limited overlap between wildlife and humans, secondary contact with farmed animals may constitute a probable route through which zoonotic viruses are transmitted to humans."

Current viral research, however, focuses disproportionately on livestock such as pigs. "Importantly, fur animals such as foxes, civets and mink have been suggested to be the potential hosts for a variety of human viruses, including influenza A virus (IAV), SARS-CoV and SARS-CoV-220–23, and outbreaks of H5N1 IAV have recently been reported in farmed European mink," the researchers added.

39 viruses with spillover potential

The team identified 125 viral species, including 36 novel viruses (those not previously characterized) and 39 at potentially high risk for cross-species transmission, including spillover into people. Most fur-farmed animals hosted 2 to 23 vertebrate-linked viral species.

Notably, 19 potentially high-risk viruses were detected in Shandong province, which contains many fur animal farms.

Sixty percent of viruses led to an expansion in known host range, including seven species of coronaviruses found in 66 fur-farmed animals. The team noted the transmission of a novel canine respiratory coronavirus to raccoon dogs and the spread of bat HKU5-like coronaviruses to mink, which they harbored in abundance in the lungs.

Three subtypes of IAV (H1N2, H5N6 and H6N2) were detected in the lungs of guinea pigs, minks, and muskrats, respectively. Guinea pigs also carried multiple zoonotic viruses—those capable of spread between animals and people—such as Japanese encephalitis virus and mammalian orthoreovirus.

"Most (n = 29) potentially high-risk viruses were sampled from east China, with a detection rate of 40.5%," the researchers wrote. "Notably, 19 potentially high-risk viruses were detected in Shandong province, which contains many fur animal farms."

'An important transmission hub'

Viruses that showed evidence of frequent host-jumping included 11 viruses already seen in people, 15 viruses not seen in people but observed in at least two mammalian orders, and 13 potentially novel high-risk viruses.

Of all studied animals, raccoon dogs and mink carried the most potentially high-risk viruses, followed by guinea pigs, rabbits and Arctic foxes. Multiple animal species were commonly infected with Coronaviridae, Paramyxoviridae, and Sedoreoviridae viruses. 

These data also reveal potential virus transmission between farmed animals and wild animals, and from humans to farmed animals, indicating that fur farming represents an important transmission hub for viral zoonoses.

"Of particular concern was the identification of Pipistrellus bat coronavirus HKU5-like viruses (subgenus Merbecovirus) in the lungs and intestines of two farmed mink," on a single farm tied to an outbreak of pneumonia, the authors wrote. "The mink HKU5-like CoVs [coronaviruses] form a lineage that is relatively closely related to viruses that were thus far reported only in bats, in which they have a history of recombination."

Paramyxoviridae, Coronaviridae, and Caliciviridae viruses were the most abundant in lung samples, while Coronaviridae, Sedoreoviridae, and Astroviridae viruses were the most abundant in the intestines.

"These data also reveal potential virus transmission between farmed animals and wild animals, and from humans to farmed animals, indicating that fur farming represents an important transmission hub for viral zoonoses," the researchers wrote.

The team called for more extensive and regular monitoring of fur-farmed animals to identify potential viral transmission routes between species and flag viruses that could jump to people, wild animals, and livestock.

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