Thursday, April 02, 2020

Susceptibility of Ferrets, Cats, Dogs & Other Domestic Animals to SARS-CoV-2

The Undisputed Queen of My Household


Five weeks ago, in Hong Kong AFCD: Dog Tests `Weakly Positive' For COVID-19, we saw the first report of a companion animal infected with the novel coronavirus.   Since then, Hong Kong has reported a second dog has been infected, and two days ago announced a Pet cat tested positive for COVID-19 virus.
In all of these cases, the assumption is that these animals contracted the virus from exposure to their already infected human companions; reverse zoonosis. 
During the H1N1 pandemic of 2009 we saw both dogs (see US: Dog Tests Positive For H1N1) and cats (see Companion Animals And Novel H1N1) infected with the virus. Given that SARS-CoV-2  appears to have originated in a mammal (bats), and has jumped species - probably at least twice - it  is not terribly surprising that exposed companion animals might be susceptible to infection as well.

There is currently no evidence that companion animals can - or have - transmitted the virus to humans, and with the number of confirmed human cases expected to exceed 1 million today (and the real number likely many times higher), you are far more likely to be infected by another person than by your pet.  
But of course, it is valuable to know which animals species are susceptible to the virus, whether it sickens them, and whether they shed the virus enough to be infectious.  
It would be very important if we discovered that the virus favored pigs, chickens, or other livestock - as those populations might promote additional viral mammalian adaptation, and continually reseed the virus into humans.

Enter Dr. Hualan Chen - one of the world's most respected virologists - and director of China's National Avian Influenza Reference Laboratory, whose work we've followed for years in this blog (see here, here and here), and who has conducted research on the susceptibility of a variety of animals to the SARS-CoV-2, the virus that causes COVID-19 in humans.

Despite its excellent pedigree, this study is on a preprint server (BioRxiv), and has not been peer reviewed, and should be viewed in that light.  First the link, and the abstract, then a brief look at a Nature article published yesterday on these findings.

Susceptibility of ferrets, cats, dogs, and different domestic animals to SARS-coronavirus-2
Hualan Chen et al.
This article is a preprint and has not been certified by peer review [what does this mean?].
Preview PDF
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the infectious disease COVID-19, which was first reported in Wuhan, China in December, 2019. Despite the tremendous efforts to control the disease, COVID-19 has now spread to over 100 countries and caused a global pandemic. 
SARS-CoV-2 is thought to have originated in bats; however, the intermediate animal sources of the virus are completely unknown. Here, we investigated the susceptibility of ferrets and animals in close contact with humans to SARS-CoV-2.
We found that SARS-CoV-2 replicates poorly in dogs, pigs, chickens, and ducks, but efficiently in ferrets and cats. We found that the virus transmits in cats via respiratory droplets. Our study provides important insights into the animal reservoirs of SARS-CoV-2 and animal management for COVID-19 control.
(Continue . . . )

A less technical overview can be found in this article in Nature:
Coronavirus can infect cats — dogs, not so much
But scientists say it’s unclear whether felines can spread the virus to people, so pet owners need not panic yet.

The good news is this virus doesn't have a great affinity for pigs, chickens, or ducks and only weakly infects dogs.  The replication reported in ferrets is hardly surprising, given that SARS-CoV-2 is a respiratory virus that is well adapted to humans.  
The implications of it replicating, and transmitting (albeit rather poorly in this study), in cats, will require further investigation. Cat-to-human transmission of a novel respiratory virus is rare, but has been reported (see EID Journal: Avian H7N2 Virus in Human Exposed to Sick Cats).
Another species I would have like to have seen included in this study are mink. They are extensively farmed in China - and around the world - and like ferrets, are highly susceptible to a number of human viral respiratory infections. A few of many studies we've looked at include:
Vet. MicroB.: Eurasian Avian-Like Swine Influenza A (H1N1) Virus from Mink in China

Nature: Semiaquatic Mammals As Intermediate Hosts For Avian Influenza
That Touch Of Mink Flu (H9N2 Edition)
I imagine there are also studies looking into the susceptibility of dromedary camels and other camelid species to this virus, as they are already known to be susceptible to MERS-CoV.  And of course, the (presumed) intermediate host species that likely transmitted the virus to humans has yet to be identified.
While it seems a lifetime ago, we are barely 3 months since the world (outside of Mainland China) became aware of this novel coronavirus, and so research is scarce. It took nearly a year for researchers to prove a connection between MERS-CoV infection in humans and camel exposure (see Camels Found With Antibodies To MERS-CoV-Like Virus).

All of which means there are probably a few surprises with SARS-CoV-2 still ahead.