Health

Stray dogs could have passed coronavirus from bats to humans, scientists say


THE new strain of coronavirus responsible for Covid-19 could have jumped from bats to humans via stray dogs, a new study suggests.

The virus, named Sars-Cov-2, may have mutated in the intestines of dogs before leaping to humans and infecting almost two million people across the world.

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 Scientists say stray dogs could have passed coronavirus from bats to humans

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Scientists say stray dogs could have passed coronavirus from bats to humansCredit: Getty Images – Getty

Early studies showed the new strain of coronavirus did originate in bats, but scientists have been trying to find which animal that transferred it from bats to humans.

They say it is critical for understanding how the virus works – and for concocting vaccines and treatments to stop its spread.

Studies have linked pangolins and snakes so far, but now a team in Canada have suggested a scenario where “the coronavirus first spread from bats to stray dogs, eating bat meat”, before jumping to humans late last year.

Lead author, Professor Xuhua Xia said the specific origins of Sars-Cov-2 are “of vital interest in the current world health crisis”.

But, other experts have questioned the latest theory.

Prof James Wood, head of Veterinary Medicine at the University of Cambridge said dog owners should not be concerned by the new findings.

He said: “I don’t see anything in this paper to support this supposition and am concerned that his paper has been published in this journal.”

Prof Wood criticised the study for relying on “far too much inference and far too little data”.

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Prof Xia, a biologist at the University of Ottawa, said their “new hypothesis” suggests that the nearest ancestor of Sars-Cov-2 – caused by a bat coronavirus – infected the intestines of dogs.

“This most likely resulted in a rapid evolution of the virus and its jump into humans,” he said.

“This suggests the importance of monitoring Sars-like coronaviruses in feral dogs in the fight against Covid-19.”

Pangolins – a scaly mammal that looks like an anteater – were previously believed to have provided the key “staging post”, and in the earliest stages of the outbreak snakes were suspected as the vector animal.

However, a complex analysis of Sars-Cov-2 genetic mutations has ruled both out as the intermediary.

The viruses found in both pangolins and snakes are “too divergent from Sars-Cov-2” to be make them the culprit.

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Prof Xia explained that humans and mammals can fight viruses thanks to a key antiviral protein called Zap.

It prevents the infection from multiplying, while parts of the DNA called CpG dinucleotides direct the immune system to attack the virus.

But single-strand coronaviruses can avoid the body’s natural defences by reducing CpG, in a similar fashion to HIV.

In his study, published in Molecular Biology and Evolution, Prof Xia analysed all 1,252 full-length betacoronavirus genomes deposited into the open access GenBank database.

He said that Sars-Cov-2 and its closest known relative, a bat coronavirus (BatCoV RaTG13), which shares 96 per cent sequence similarity, have the lowest amount of CpG among its close coronavirus relatives.

Only genomes from canine coronaviruses, which have already caused a highly contagious intestinal disease worldwide in dogs, have similar genomic values, according to the study.

Dogs also have coronaviruses which affect their respiratory systems as well as their digestive systems, but the digestive kind has much lower CpG values, the paper notes.

The cellular receptor for Sars-Cov-2 entry into the cell is called ACE2, which is “pervasively expressed in the human digestive system … with relatively low expression in the lung”, the study says.

It adds: “This is consistent with the interpretation that the low CpG in Sars-Cov-2 was acquired by the ancestor of Sars-Cov-2 evolving in mammalian digestive systems.

“The interpretation is further corroborated by a recent report that a high proportion of Covid-19 patients also suffer from digestive discomfort.

“In fact, 48.5 per cent presented with digestive symptoms as their chief complaint.

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“In particular, live Sars-Cov-2 virus was isolated from the stool of a Covid-19 patient.

“In this context, it is significant that BatCoV RaTG13 … was isolated from a fecal swab.

“These observations are consistent with the hypothesis that Sars-Cov-2 has evolved in mammalian intestine or tissues associated with the intestine.”

A study of the first 12 patients in the US found one reported diarrhoea as the initial symptom before developing fever and cough.

Stool samples from seven out of ten tested positive for Covid-19, including three with diarrhoea.

Dogs are often observed to lick their anal and genital regions, not only during mating but also in other circumstances.

Such behaviour would facilitate viral transmission from the digestive to the respiratory system.

It also fits the picture of a pathogen that causes gastrointestinal, respiratory and lung disease.

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Nearly two million people have contracted Sars-Cov-2 since it first appeared at a seafood market in Wuhan, China, in late 2019, according to a global tracker by Johns Hopkins University.

More than 120,000 people have died after developing Covid-19, the disease caused by the virus.

It’s not the first time bats have been the source of deadly viruses that have jumped to humans.

Ebola, rabies and Sars all originated in bats, the 2002 Sars outbreak was caused by the virus jumping from horseshoe bats to civets before infecting humans.

Cases of Covid-19 first emerged in December and were linked to a wet market in Wuhan, China, where wild animals including marmots, birds, rabbits, bats and snakes, are traded illegally.

Experts warn these horrific sites are a “ticking time bomb” and could lead to a new disease much like Covid-19 which has swept the world.

Coronavirus fury as wet markets STILL selling wildlife to eat despite ‘sparking deadly pandemic’





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