Rats sold in Southeast Asian markets and restaurants contain more coronavirus, research shows.
The proportion of positive rats increased as live animals were moved from the field to the menu, suggesting that they take on viruses in the process.
The strains detected are different from Covid-19 and are not considered dangerous to human health. However, scientists have long warned that wildlife trade could be an incubator for disease.
Mixing multiple coronaviruses and seemingly amplifying them along the supply chain in restaurants suggests “maximum risk to end consumers,” said a team of researchers from the U.S. and Vietnam.
The origin of the current pandemic is thought to lie in the wildlife trade, and the disease occurs in bats and spreads to humans through another, as yet unidentified species.
The new discoveries, which are considered preliminary, apply to rats, but can also be applied to other wildlife, such as civets and pangolins, which are also collected, transported and confined in large numbers.
“While these are not dangerous viruses, they provide information on how viruses can intensify under these conditions,” said Sarah Olson of the New York-based conservation group WCS, which conducted the research along with experts from Vietnam.
Co-researcher Amanda Fine, also a WCS, added: “Wildlife supply chains and the conditions that animals have while in the supply chain appear to greatly increase the prevalence of coronavirus.”
Rats are a common source of food in Vietnam, where they are trapped in rice fields and transported to markets and restaurants to be butchered as a fresh source of meat. Rodents are also bred on wildlife farms, along with other animals, such as chamois.
Six known coronaviruses were detected in samples taken at 70 sites in Vietnam in 2013 and 2014. A high proportion of positive samples were found in Polish rats intended for human consumption. The share of ratios increased positively along the supply chain:
Farms – 6%
Dealers – 21%
Large markets – 32%
Restaurants – 56%.
Detection rates in rodent populations in their “natural” habitat are closer to 0-2%, the researchers said.
The study was conducted with animal health experts in Vietnam, who are considering banning the trade and consumption of wild animals. Appears in the journal before printing bioRxiv before review.
Conservation experts say the coronavirus pandemic is a turning point in combating 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 the breeding and consumption of live wildlife due to the outbreak, but there are still holes like wildlife trade for drugs, pets and scientific research.
China has reported that it has removed pangolins from the official list of traditional Chinese medicine treatments. Libra is very popular with traditional Chinese doctors, while pangolin meat is considered a delicacy.