The British coronavirus variant may have come from dogs, say researchers

According to a study by Chinese scientists, a coronavirus variant first discovered in Britain can come from dogs.

The Shanghai-based researchers who traced the early evolution of variant B117, which caused a new wave of cases in several countries, could not find its footprint in viral samples collected from humans worldwide.

But as they expanded their search for animals, they discovered some early forms of B117 on dogs, including one sample taken in the United States last year.

“Such progenitor variants contained most or all of the mutations of the earlier variant B117 in the Canidae family populations, and they may have washed back to humans after a rapid period of mutation,” wrote Professor Chen Luonan and colleagues at the State Key Laboratory of Cell . Biology in a non-peer-reviewed article posted last Friday on biorxiv.org.

The emergence of the B117 variant surprised researchers. After being isolated from two patients in southeast England and London last September, it quickly became the dominant strain in the UK and many other countries and spread faster than previous strains.

Some experts believe that the variant may have originated from local communities under the selective pressure of antiviral drugs used during the pandemic. According to one prevailing theory, it suddenly appeared in the United Kingdom and then spread to other parts of the world.

But the variant has nine different mutations that, according to Chen and colleagues, were rarely, if ever, found in earlier human strains.

These mutations did not occur in adjacent genes, but spread throughout the viral genome. The chance of all these mutations appearing at the same time is extremely low.

The Shanghai team believes that these nine mutations have built up one after the other. Their model suggested that the variant may have originated outside the UK and received the mutations on a non-human host. Dogs were the most likely suspects, followed by minks or cats.

Qu Liandong, a professor of virology at the Harbin Veterinary Research Institute who was not involved in the study, said more thorough evidence would be needed to substantiate the theory.

The strains found in dogs were not quite the same as the first in the British patient. Although the number of genomic sequences obtained by researchers worldwide has reached hundreds of thousands, it is small compared to the total number of patients out there.

Some early forms of the B117 variant may be missed by sampling programs, according to Qu.

But when pets like dogs turn out to be the host, “we have a big problem,” Qu said, studying communicable diseases shared by humans and animals.

“Almost all of our measures to combat the pandemic so far only concern people. “If there are animals involved, it will completely change the game,” he said.

When bird flu breaks out in a chicken farm, all the chickens there must be killed, according to global standard practices. If the disease can infect humans, all susceptible animals – including healthy animals – in the affected area must be eliminated.

Dogs are important human companions, but if it is proven that they can carry or produce mutated variants of the Sars-CoV-2 virus, they can also be eliminated, Qu said.

An alternative is to give the vaccines to the animals. ‘But we can not give the vaccines to the dogs. We may have to develop completely new versions. We are already struggling to vaccinate people. How can the program be expanded to cover dogs or other animals? ”Qu added.

There is growing concern that B117 can make dogs very ill. Veterinarians near London noticed a sudden increase in pets earlier this year, including dogs and cats, who had myocarditis, and many of these animals tested positive, according to a Reuters report in March.

Humans and animals have different immune systems and it is usually difficult for a virus to jump from one species to another.

The Sars-CoV-2 virus is thought to have originated in bats, but may have taken decades to adapt to humans. When and where it made the leap from animal to human remains unclear.

Chen’s team said the B117 variant has a unique evolutionary strategy to increase its infectivity so that it can spread more easily from one host to another, while at the same time reducing the number of specimens it makes in a host.

Whether the strategy helped the variant bridge the species gap remains to be seen, according to the researchers.

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