The British coronavirus variant may come from dogs, researchers say

A variant of coronavirus first discovered in Britain may have come from dogs, according to a study by Chinese scientists.

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

But when they expanded the search to animals, they discovered some early forms of B117 in dogs, including a sample taken in the United States last July.

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

The emergence of the B117 variant has puzzled researchers. After being isolated from two patients in Kent in South East England and London last September, it quickly became the dominant species in the UK and many other countries, spreading faster than previous species.

Some experts believe that the variant may have emerged from local communities under the selective pressure of antivirals used during the pandemic. According to a prevailing theory, it suddenly appeared in the UK and then spread to other parts of the world.

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

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

The Shanghai team believes these nine mutations have built up one by one. Their model suggested that the variant may have originated outside of the UK and acquired 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 Harbin Veterinary Research Institute, who was not involved in the study, said more solid evidence would be needed to support the theory.

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

According to Qu.

But if pets like dogs turn out to be the host, “we’ll have a big problem,” said Qu, who studies infectious diseases shared by humans and animals.

“Almost all of our measures to combat the pandemic have so far only concerned humans. When animals are involved, the game will change completely, ”he said.

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

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

An alternative is to give the animals vaccines. ‘But we can’t give the dogs human vaccines. We may need to develop some completely new versions. We are already struggling to vaccinate people. How can the program be extended to dogs or other animals? Qu added.

There is growing concern that B117 could make dogs very sick. Vets near London noticed a sudden increase in pets – including dogs and cats – early this year suffering from myocarditis, a serious heart disease, and many of these animals tested positive for the variant, 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 believed to have originated in bats, but it could 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 had a unique evolutionary strategy to increase infectivity so that it can spread more easily from one host to another, but at the same time reduces the number of copies it makes in a host.

Whether this strategy helped the variant bridge the species gap should be further explored, according to the researchers.

RELATED VIDEO