Scientists claim that COVID-19 was passed to humans by dogs: Study

It was earlier believed that COVID-19 pandemic started with pangolins. Studies suggested that the deadly virus was transmitted to humans by bats. However, a new study by a team of researchers at a Canadian university claims that the viral transfer may have actually happened from dogs to humans.

According to Mirror, scientists at the University of Ottawa suggest that humans may have received the coronavirus from an intermediate animal, dogs. The lead author of the study, Professor Xuhua Xia suggests the virus was first transferred to stray dogs by eating infected bat meat.

"Our observations have allowed the formation of a new hypothesis for the origin and initial transmission," Xia, a biologist at the university suggests.

He goes on to explain that eating bat meat may have first infected the dogs' intestines, where the virus may have got the best environment for replication and then "jumped into humans."

"The ancestor of Covid-19 and its nearest relative, a bat coronavirus, infected the intestine of dogs, most likely resulting in rapid evolution of the virus and its jump into humans. This suggests the importance of monitoring SARS-like coronaviruses in feral dogs in the fight against Covid-19," Xia explains.

The report reveals that scientists believe that the pandemic began in bats since it remains one of the oldest hosts of the virus. They are also believed to be responsible for other diseases such as Ebola, rabies, and Sars, previously. However, human and bats interaction remains zero to a minimum, which got the scientists to believe that there could be another animal involved in the transmission.

The research that was published in the journal called Molecular Biology and Evolution studied the key human protein ZAP and focused on the coronavirus genome called CpG. ZAP in humans is an antiviral protein that provides protection from viruses and presents replication.

As per the report, coronavirus can overpower ZAP by reducing the levels of CpG and provide a proper environment to evolve.

"A virus with an increased amount of CpG would be better targeted by the host immune system, and result in reduced virulence, which would be akin to natural vaccines," Xia explained.

It was found that the dogs' genomes have lower CpG values that are a match to those observed in COVID-19. And humans are reportedly only the other species to generate coronavirus genomes with lower levels of CpG values.

"This is consistent with the interpretation the low CpG in COVID-19 was acquired by the ancestor evolving in mammalian digestive systems. 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% presented with digestive symptoms as their chief complaint," Xia said in the study.

The report refers to a study of first 12 COVID-19 patients in the US out of which one reported to have experienced diarrhoea before any other common coronavirus symptoms such as dry cough or high fever.

The study suggests that the viral transmission could happen when a person touches the dog's faeces or was licked by a dog, who frequently lick their anal or genital areas.

"In this context, it is significant the bat coronavirus (BatCoV RaTG13) was isolated from a faecal swab. These observations are consistent with the hypothesis that COVID-19 has evolved in mammalian intestine or tissues associated with intestine," Xia said.

This theory may not prove to be a very convincing one for other scientists.

Prof Mick Watson, Personal Chair of Bioinformatics and Computational Biology at the Roslin Institute deemed the theory "speculative." "The theory that SARS-CoV2 originated in dogs seems to stem from speculation about CpG and high ZAP expression. This is speculative at best and certainly isn't strong evidence for the link," Watson said.

Meanwhile, Xia suggests that it is important to monitor the development of SARS-like coronaviruses in feral dogs.

"There is near a 100% likelihood that there was just one transmission," Vanderbilt's Schaffner infectious disease expert Dr. William Schaffner, a professor of preventive medicine and infectious disease at Vanderbilt University School of Medicine in Nashville said responding to the theory as quoted by CNN. "This is a powerful statement -- one transmission from some animal source to a human that likely occurred in a wet market in China. It happened only once, and all the other infections in humans that have occurred have come from that one instance of transmission," he added.

In addition, Schaffner said that we don't need to worry about getting it from our dogs or giving it to our dogs.