Are pets susceptible to infection and transmission of SARS-CoV-2? Apparently not, according to researchers at the Institut Pasteur and the National Veterinary School in Alfort. They tested several cats and dogs that had been in close contact with humans who tested positive for SARS-CoV-2 or had clinical signs of Covid-19 disease. No animal in this study carried the virus.
The question of the role of domestic animals in the spread of SARS-CoV-2 is very important. Coronaviruses are organized into four genera: αCoV, βCoV, ƔCoV and ẟCoV. ΑCoV and ẟCoV are present in pigs, while ƔCoV frequently infect wild and farmed birds. In cats, the feline coronavirus (FCoV), responsible for feline infectious peritonitis, belongs to the genus αCoV, while in dogs, two coronaviruses are described, the canine enteric coronavirus belonging to the genus αCoV and the canine respiratory coronavirus belonging to the genus βCoV. However, the human coronaviruses known to date also belong to the genera αCoV and βCoV.
Besides the animals already identified as reservoirs (the pangolin and the bat), certain occasional transmissions between humans and companion animals have been documented. In early April, a female tiger from the New York Zoo was tested positive for SARS-CoV-2. The animal had clinical respiratory signs on March 27, 2020. Three other tigers and three lions showed clinical signs (dry cough and difficulty breathing) but were not sampled.
On March 18, 2020, a cat belonging to a person with Covid-19 tested positive for SARS-CoV-2 in Belgium. The presence of viral RNA from the SARS-CoV-2 virus has been demonstrated in the feces and vomit of cats that have clinical digestive and respiratory signs.
No animals tested positive
In a text published via the bioRxiv prepublication site, the researchers tested, by PCR and by serological test (antibodies directed against the S1 domain of the Spike S protein and against the C-terminal end of the viral nucleoprotein), 21 animals domestic workers (9 cats and 12 dogs) living in very close contact with 18 students from the Alfort veterinary school, some of whom were confirmed or suspected cases of Covid-19. Although some animals have shown clinical signs compatible with coronavirus infection, no animal has tested positive for SARS-CoV-2 despite the close proximity to their owners. The 100% of cat owners and 33% of dog owners sleep with their pet, while 78% of cat owners and 92% of dog owners let their faces be licked.
The samples collected from these animals during the current Covid-19 epidemic were compared with 21 pre-epidemic samples. No sample from either group was positive for SARS-CoV-2. “ These initial data are preliminary and may allow a better evaluation of the host range of SARS-CoV-2 under exposure conditions in a natural environment. ”, explain the authors. These initial results suggest that the SARS-CoV-2 virus is more difficult to infect animals, even when the latter are in contact with infected owners.
Researchers predict that more studies will be needed to accurately characterize the possible role of pets, especially felines, as an intermediate vector host for SARS-CoV-2. These studies should include larger populations and specifically study the role of the age of the animals as well as the surrounding viral load.
The current study has several limitations: only two of the 20 owners are confirmed cases of Covid-19, and 11 (including the two confirmed cases) were not tested by PCR but presented symptoms compatible with the pathology: fever , cough, anosmia. The last seven owners had not been tested, and were all asymptomatic at the time of collection.
ANSES wants to be reassuring
In the current state of available data, the National Agency for Food, Environmental and Occupational Health Safety (ANSES) believes, however, in a notice published on Monday, April 20, that there is currently no evidence scientist showing that domestic animals (farm and companion animals) play an epidemiological role in the spread of SARS-CoV-2.
Although SARS-CoV-2 is of animal origin, the ANSES “Covid-19” collective emergency expertise group (GECU) estimates that the transmission of SARS-CoV-2 from humans to a domestic animal species “ cannot be completely ruled out, but an adaptation to it seems currently unlikely ”.
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