Rats sold in markets and restaurants in Southeast Asia harbor multiple coronaviruses, study shows.
The proportion of positive cases has increased as animals have been moved from “fork to fork”, suggesting that they have been picking up viruses in the process.
The strains detected are different from Covid-19 and are not expected to be harmful to human health.
But scientists have long warned that wildlife trade can be an incubator for the disease.
The mixture of several coronaviruses, and their apparent amplification of the supply chain in restaurants, suggests “maximum risk to end consumers,” said a team of researchers from the United States and Vietnam.
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The origins of the current pandemic are thought to trade in wildlife, with emerging diseases in bats and to jump to people via another, not yet identified, species.
The new findings, considered preliminary, relate to rats, but may apply to other wild animals, such as civets and pangolins, which are also collected, transported and enclosed in large numbers.
“While they are not dangerous viruses, they offer information on how viruses can be amplified under these conditions,” said Sarah Olsen of New York, conservation group, WCS, who led the study alongside experts in Vietnam.
Co-researcher Amanda Fine, also from WCS, added: “Wildlife in the supply chain, and the living conditions of animals in the supply chain, appear to greatly increase the prevalence of coronaviruses. ”
Rats are often a source of food in Vietnam, where they are seized from rice fields and transported to markets and restaurants, to be slaughtered as a new source of meat. Rodents are also raised in farm fauna, along with other animals such as porcupines.
Six known coronaviruses were detected in samples collected from 70 sites in Vietnam in 2013 and 2014. A high proportion of positive samples were found in the field of rats intended for human consumption. The proportion of positive cases increased significantly along the supply chain:
Detection rates in rodent populations in their “natural” habitat are closer to 0-2%, the researchers said.
The study was carried out with animal health experts in Vietnam, who are considering a ban on wildlife trade and consumption. It appears in the bioRxiv newspaper pre-print in advance of the peer review.
Conservation experts say the pandemic coronavirus is a defining moment to curb the global wildlife trade. Wet markets can be “time bombs” for epidemics, they warn, bringing together different species that can shed and spread the virus.
China has banned agriculture and consumption of living wildlife in the wake of the outbreak, however gaps remain, such as the trade in wild animals for medicine, pets and scientific research.
China has opted to eliminate pangolins from the official list of traditional Chinese medicine treatments. The scales are highly coveted by practitioners of traditional Chinese medicine, while pangolin meat is considered a delicacy.
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