Our feline friends are also vulnerable to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, according to new research posted to the preprint server bioRxiv*. The researchers diagnosed two cats living in France with mild symptomatic COVID-19 illness. The virus was most likely transmitted from their owners.
Previous studies have shown increasing evidence of feline-to-feline transmission and human-to-feline SARS-CoV-2 transmission — but not the other way around. Feline infection by one of the variants of concern remains unknown but is a rising concern for pet and non-pet owners.
The researchers write:
"This question will become rapidly crucial in the very near future as the British variant, known to be much more infectious, is currently removing the ancestral variant of SARS-CoV-2 in France as well in other countries of Europe. Therefore, it is becoming more and more important to implement a One Health approach to face SARS-CoV-2 epidemic that takes into account infection and viral circulation in pets."
The two cats came from two separate households during France's second coronavirus wave from October 2020 to November 2020. The team collected RNA samples using nasopharyngeal and rectal samples. They use PCR to confirm a coronavirus diagnosis. One cat underwent serological analysis for antibodies specific to either the nucleocapsid protein (N protein) or the spike protein.
The first participant was a 5-year-old female European cat who was raised in a single-pet indoor-only household. Her only contact with the outside world during the pandemic was her owner. She had vaccinations 3 years ago and had no previous history of medical conditions.
Her owner was positive with symptomatic SARS-CoV-2 infection, and 10 days later, on October 24, 2020, the cat started showing symptoms as well. She showed continuous sneezing with non-purulent nasal secretions; there was an absence of digestive and other symptoms indicative of SARS-CoV-2.
Five days after symptom presentation, the cat displayed pink mucous membranes, an increased heartbeat of 175 bpm, increased rectal temperature ranging from 38°C-39°C, dehydration, urea seric concentration of 0.49g/l, and a creatinine seric concentration of 12.7mg/l.
The cat was treated with one doxybactin tablet for 10 days and a daily dose of Meloxoral for 3 days, with a noticeable improvement 3 days into treatment.
The team assessed serum from blood samples to look for SARS-CoV-2 antibodies following recovery. They found antibodies specific to the N protein, the spike protein's receptor binding domain, and tri-spike SARS-CoV-2 proteins. Because of the poor conservation of swab samples, the researchers could not perform genomic surveillance for SARS-CoV-2 variants.
The second participant was a 13-year-old male European with a history of chronic rhinitis and living in a multi-pet household. He tested positive for SARS-CoV-2 infection after the pet owner — who was also positive — reported mild symptoms. Further testing found retro-mandibular adenopathy but no other symptoms.
Similar to the first cat, poor storage of samples made it difficult to evaluate the SARS-CoV-2 genome. The researchers only managed to sequence 5 partial fragments from oropharyngeal swabs. They did not find a 11288-11296 deletion, suggesting coronavirus infection was not from the B.1.1.7, B.1.351, and P.1 variant. While the researchers did not find any evidence of variants because it was potentially before their emergence, they note understanding the variants' effects on cats is limited. It remains unknown how the variants affect the transmissibility and severity of the disease.
One sequenced fragment had a genetic mutation to the amino acid Q57H. The researchers note the H57 mutation has been found worldwide and was present in about 70% of sequences analyzed in France from October and December 2020.
The results suggest their owners most likely infected both cats. "Although we cannot definitively rule out infection of the cats by an individual outside the household, the information provided by owners, including the exclusive and unique contact with its owner for cat 1 and the general deterioration in the condition of all cats of the cat 2 owner, strongly suggests a transmission from owners to cats," writes the research team.
*bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.