Xuhua Xia of the University of Ottawa proposes that stray dogs may have been the intermediary animal that spread the coronavirus from bats to humans, instead of the pangolins, as initially thought.

Xia mentions a possible scenario wherein the coronavirus could have first spread from bats to stray dogs that were consuming bat meat. Canadian researchers who analyzed the coronavirus genome contend that only transmission from dogs can explain their findings. He suggests the importance of monitoring SARS-like coronaviruses in untamed dogs in the fight against COVID-19.

Their study, however, met criticism from other scientists who claimed that they jumped into such assumptions with only so little data. University of Cambridge veterinary medicine expert, James Wood, said that dog owners should be concerned as a result of the reported study since the proof they incurred was insufficient.

Knowing how coronavirus came to infect humans is crucial for understanding how the virus works. It would also be a tremendous breakthrough for formulating vaccines and treatments to stop its spread.

Eliminating Pangolins From the Equation

Pangolins were previously believed to have been the carrier of the virus from bat en route to humans. According to the International Union for Conservation of Nature, pangolins are the most illegally traded mammal in the world. The scaly mammals are prized for their meat and are also used for medicinal purposes.

However, further investigation of COVID-19 mutations has ruled them out as the direct source of the first human infection. The same analysis also ruled the possibility of the virus coming directly from bats.

To have been transmitted from pangolins, the common ancestor of COVID-19 and coronavirus in pangolins would have had to have evolved back in 1882, which was simply 'too far back in time', according to Xia.

He argues that dogs provide a far more credible explanation for how the virus made its way into humans.

Putting the Spotlight on Dogs

In their study, Professor Xia and colleagues investigated an essential antiviral protein, known as ZAP. It is capable of stopping a virus in its tracks by preventing its multiplication and downgrading its genome.

It works by targeting a pair of chemical letters called 'CpG dinucleotides', which can be found within the virus' RNA genome. It acts as an indication that one's immune system can use help to seek and destroy a virus.

Professor Xia claims that only genomes from dog coronaviruses have CpG values similar to the ones observed in COVID-19. He added that dogs and humans were the only host species his team found that was capable of producing coronavirus genomes with low genomic CpG values.

A study of the first 12 patients in the US found that one had reported diarrhea as their initial symptom before they developed a fever and a cough. Moreover, stool samples from seven out of 10 patients who tested positive for COVID-19 displayed diarrhea as a symptom.

Dogs are often observed to lick their anal and genital parts. Such behavior had the potential to facilitate viral transmission from the digestive to the respiratory system, Xia said. 'In this context, it is significant the bat coronavirus was confined from a fecal swab,' Xia added.