The first known case dates back to the beginning of March: a Pomeranian puppy was infected by its owner, who had contracted the coronavirus in Hong Kong.
Since then there have been other reports, but, most importantly, the first systematic studies have got underway, even if for now these involve relatively limited numbers. The result, however, is always the same: pets – cats and dogs, in particular – can be infected by humans, but not vice-versa. This is also confirmed by two studies that have recently come to light.
The first, presented at the virtual congress of the European Society of Clinical Microbiology and Infectious Diseases by a group of Canadian vets, was conducted on 18 dogs and 17 cats of people with the coronavirus.
All the swabs were negative, except for that of one cat. The serological tests carried out on the blood of 8 cats and 10 dogs told a different story: half of the cats had developed IgM, i.e. the first immunoglobulins (antibodies) that are produced after an infection, and 38% had IgG, the immunoglobulins that kick in afterwards. All the cats that tested positive had also shown respiratory symptoms during the same period as their owners. As for the dogs, 20% had IgG, none had IgM and one had the typical symptoms of Covid-19.
The second study, published in the scientific journal PNAS by researchers from the University of Barcelona involved a Spanish cat, called Negrito. An in-depth analysis was carried out on this cat after its death to demonstrate that the SARS-CoV-2 coronavirus that had infected the cat was genetically identical to the virus isolated in its owner.
Also, in recent months various studies have reached the same conclusions, like the one appearing in the scientific archive BioRXiv, awaiting review. This study involved 540 dogs and 277 cats in the north of Italy that were analysed between March and May. None of them had a positive swab, but the serological tests show that approximately 3% of the dogs and 4% of the cats had antibodies, proving the existence of an infection.
As for cats, on the other hand, a study published in the journal Emerging Microbes & Infections involving around one hundred cats of various origins (strays, hosted in catteries and pets) from Wuhan (China) showed an incidence of specific antibodies of 15%, therefore higher than the numbers found in other countries.
In the meantime, the potential danger of minks has emerged, and especially, of mink farms. A study carried out on 16 Dutch farms and also published early on BioRXiv (awaiting review by other experts) showed that 66 out of 99 farm workers that were tested had the infection. Also, in this case it would have been the humans that infected the animals, but then the virus would have also done the reverse, feeding a dangerous circuit that they are now trying to break.
Finally, a study published in the journal PNAS has shown that there are at least 410 species of vertebrate animals to be considered as potential vehicles of transmission of the SARS-CoV-2 coronavirus, because these are the species that express the ACE2 cell receptors to which the virus attaches.
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