Since the beginning of the Covid-19 pandemic, the virus has spread among humans but also among pets, livestock and wild animals. Cats appear to be particularly susceptible to contracting SARS-CoV-2, although most of the time they show no symptoms and do not transmit it to humans or other cats. However, although Covid-19 circulates quietly among animals, the risk of it mutating into a dangerous disease is not non-existent.
A recent study, published in the scientific journal MDPI, reports the case of a domestic cat from Pennsylvania who was diagnosed positive for Covid-19 in September 2021. Subsequent genomic tests identified that he had contracted the Delta AY.3 variant, the same one that circulated in cats. humans at the time. This case confirms that unfortunately the variants – at least up to the Delta – also affect animals. But on the bright side, the study results suggest that the virus doesn’t mutate much in our feline companions.
The researchers analyzed 4,200 sequences of human samples positive for Covid-19. According to the results, less than 5% contained the 10 nucleotide variants – DNA sequence variations – found in the cat’s sample. Moreover, seven of them were silent, which means that they did not cause any significant change. “Our conclusion is that the cat was infected with a virus that was somehow similar” that of humans, says veterinarian Elizabeth Lennon of the University of Pennsylvania.
Another “covid” cat
This study is the first to officially identify the Delta variant in companion animals in the United States. Yet when researched, the authors learned that another cat in Virginia had contracted it a month earlier.
Both cat-derived AY.3 genomes showed few nucleotide differences compared to human samples. “Despite our research, a larger data set is needed to detail our findings”say the researchers in the report.
For the Pennsylvania cat, a nasal test was not enough to diagnose SARS-CoV-2, but a fecal test was. Upon arrival to medical care, the cat had been suffering from anorexia, lethargy, vomiting and loose stools for several days. Its owner had contracted the virus eleven days earlier, but he had isolated himself from his animal so as not to make it sick.
When scientists discovered the cat had the Delta variant, they wanted to compare the animal’s swab and that of its owner to see if there had been transmission. However, its owner had already recovered from Covid-19. The researchers therefore could not find out how the cat had been infected or if there was any correlation between the two cases.
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“One of the key takeaways here is that as different variants of SARS-CoV-2 emerge, they appear to retain the ability to infect a wide range of species”concludes Elizabeth Lennon.
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