No real Covid-19 threat but happy to social distance anyway/Craig Medred photo

Forget the scare about dogs being potential carriers of the pandemic SARS-CoV-2 virus; it’s cats that are the real danger, according to Chinese researchers probing potential non-human carriers.

And maybe too the pigs and pangolins.

“SARS-CoV-2 replicate poorly in dog,” a team of more than four-dozen of Asian nation’s scientists reported Sunday in a study posted at bioRxiv, the preprint server for biology.

The study left open a sliver of a possibility a dog could be a threat to its human companion, but kicked the door wide open on cats, pangolins and pigs. All have been, as the Chinese put it, “permissive” toward the virus that causes the sometimes deadly disease COVID-19.

Pangolins are mammals with scales that make them look more like reptiles. Sometimes described as “scaled ant-eaters,” the are widely trafficked in Asia where “their meat is considered a delicacy and pangolin scales are used in traditional medicine and folk remedies,” according to the World Wildlife Fund.

They are not reported to make good pets unlike cats or to a lesser extent hamsters, which have previously been liked to SARS-CoV-2.

“A detailed, comparative analysis among cat, pangolin and hamster deciphered that proportion of SARS-CoV-2 target cells in cat was much higher than pangolin and hamster, implying that cats are more susceptible to SARS-CoV-2,” the Chinese reported. “Besides, as a companion animal, cats interact with humans more frequently than pangolins, thus we proposed that cats should be closely monitored in the current COVID pandemic.”

Pangolins are already believed to have been a player in the global pandemic.

Geneticists from Duke University, the Los Alamos National Laboratory, the University of Texas at El Paso and New York University have linked SARS-CoV-2 to bats, but say it appears to have jumped from bats to pangolins where the virus grabbed a gene fragment that enhanced its ability to infect humans.

Not your typical pet, a Sunda pangolin/
Frendi Apen Irawan, Wikimedia Commons

Biggest target

When and where the virus made the jump from pangolins to humans – if in fact that is exactly what happened – is unclear. SARS-CoV-2 first gained international attention in December when Chinese officials revealed a new, previously unknown virus had reached epidemic proportions in that county.

Over the course of the next two months, the virus went worldwide as the epidemic grew into a pandemic.

Scientists at Harvard have, however, suggested the disease outbreak might have started as early as summer in China. They reached the conclusion by tapping into the internet.

“Digital epidemiology and non-traditional data streams, such as satellite imagery and internet search trends, have previously been harnessed for respiratory disease surveillance,” they wrote. “These sources have been shown to be early indicators of epidemics and sensitive to trends that may otherwise go undetected by traditional public health surveillance mechanisms.

“In this study, we use two of these previously validated data streams to look for indicators of potential COVID-19 disease prior to December 2019. First, using vehicle counts extracted from high-resolution satellite imagery of hospital parking lots in Wuhan, we aim to estimate trends in hospital occupancy and its association with influenza-like illness trends. This method has been demonstrated as an effective proxy for detecting hospital traffic related to respiratory illness in Latin America.”

They coupled that information to increases in internet searches for symptoms related to COVID-19. They reported hospitals getting busy in August with internet traffic accelerating at the same time as people sought information on symptoms more often linked to COVID-19 than the flu.

“While we cannot confirm if the increased volume was directly related to the new virus, our evidence supports other recent work showing that emergence happened before identification at the Huanan Seafood market,” they concluded. “These findings also corroborate the hypothesis that the virus emerged naturally in southern China and was potentially already circulating at the time of the Wuhan cluster.”

As of this point, however, no Pangolin Zero – the hypothetical source of a pandemic that has killed to date 439,000 people around the globe – has not been found. And lots of other animals have popped up as potential carriers of the disease.

Mink in the Netherlands caught the disease in April and are believed to have later spread it to mink-farm workers.

The breakout has, however, proven somewhat confusing in that mink farms in nearby Denmark, the world’s largest mink producer, have seen no outbreaks, and farmers in China, another major mink producer, say the same.

Still, “the Dutch outbreaks have alarmed people in North Brabant province, where mink farms are concentrated. The region’s burgeoning goat industry caused the world’s largest human epidemic of Q fever between 2007 and 2009,” Science magazine reported.

Butting in

Goats are also potential carriers of SARS-CoV-2 along with the cats, pangolins and pigs, according to the new Chinese study.

“Goat share highly similar ACE2 amino acids sequence with pig and human, implying that goat ACE2 might have similar capability for mediating virus entering into host cells,” the study says.

“Cell receptor angiotensin-converting enzyme 2” or ACE2 has been identified as the so-called “target cell” to which the virus attaches itself in order to infect humans and animals.

“Given that the species barrier of SARS-CoV-2 was estimated to be relatively low and livestock, poultry and pets have very close contact with humans, it is crucial to evaluate animal susceptibility to SARS-CoV-2,” the Chinese warned.

Thus they scanned “11 representative species in pets, livestock, poultry, and wildlife” to try to determine which post the greatest threats to humans.

“Notably, the proportion of SARS-CoV-2 target cells in cat was found considerably higher than other species we investigated,” they found, “and SARS-CoV-2 target cells were detected in multiple cell types of domestic pig, implying the necessity to carefully evaluate the risk of cats during the current COVID-19 pandemic and keep pigs under surveillance for the possibility of becoming intermediate hosts in future coronavirus outbreak.”

Dogs did not appear nearly as dangerous as pets.

But the truly safe animals? Birds.

“No SARS-CoV-2 target cells were found in lung cells of poultry (chicken, duck,
goose and pigeon),” the study reported. The finding is consistent with that of other studies.

The Chinese said their work could provide a model for screening  “the susceptibility of all existing viruses on all existing species in an unbiased manner. With the development of single-cell sequencing techniques and the progress of international single-cell atlas collaborative projects, (an) atlas for more species could be generated at an accelerated speed. We anticipate that the information gained from the present study will certainly augment future research work, and provide some novel insights about the prevention and control strategies against SARS-CoV-2 along with many other harmful viruses.”

The work has yet to be peer-reviewed; it is always possible flaws will be found in the research. But it should comfort dog owners concerned about early reports of dogs infected with COVID-19.

As for cat owners, it might be time to think about trading Garfield in on a Tweety bird or at the very least, masking the cat.

Or maybe even getting into the cat-masking business.

The global market for disposable, human face masks is reported to have reached near $75 billion in the first quarter of this year and is expected to show a compound annual growth rate of 57 percent through 2027, according to Grand View Research.

Dog muzzle masks and respirators are already available on the market, but there appear at this time to be no similar devices to put on your cat to keep it from infecting you.