More details on the "Negrito" case, the first SARS-CoV-2 infected cat in Spain

On May 8, IRTA notified the first case of a SARS-CoV-2 infected cat in Spain. It was a 4 year old cat, Negrito, living with a family affected by COVID-19 with one reported case of death. Coinciding with these events, the animal presented serious respiratory difficulties and was taken to the Sant Mori Veterinary Hospital in Badalona, where he was diagnosed with a heart condition, and due to his terminal condition, it was decided to euthanize him. The necropsy, carried out in the High Level Biosecurity facilities of the Animal Health Research Center IRTA-CReSA, confirmed that Negrito suffered from a feline hypertrophic cardiomyopathy and that his death was not caused by the new coronavirus. However, the PCR test confirmed that the animal had been infected with SARS-CoV-2 but with a very low and residual viral load.

So far, there have been few cases of SARS-CoV-2 infection in cats worldwide, so researchers have deepened the study of the case and recently published it in the Proceedings of the National Academy of Sciences (PNAS). To do this, they tested the blood of the Negrito cat and another cat that also lived in the same home, Whisky, which had no signs of disease. The analyses, carried out by the IrsiCaixa AIDS Research Institute –a centre jointly promoted by the "la Caixa" Foundation and the Ministry of Health of the Government of Catalonia– show that both cats had developed antibodies against SARS-CoV-2. "In both cases we have detected neutralising antibodies, that is, they have the capacity to bind to the virus and block it", explains Julià Blanco, IGTP researcher at IrsiCaixa, "this is important as it shows us that the cats' immune system can cope with SARS-CoV-2 and, in this particular case, protect them from developing symptoms", he adds.

There are currently experimental studies showing that cats, as well as getting infected with SARS-CoV-2, can transmit it to other cats in their close circle, even without clinical signs. However, researchers first suspected that both Negrito and Whisky would have been infected from their owners because they had not been in contact with other cats. To prove this, the IrsiCaixa team analysed the genetic sequence of the virus in Negrito and found that "it has a 99.9% similarity to the virus of the owner who died. This suggests that the cat was directly infected from family members", explains Marc Noguera-Julián, IrsiCaixa's researcher.

Considering the number of people infected worldwide and the few reported cases of animals, experts keep remarking that "pets play an insignificant role in the epidemiology of SARS-CoV-2 and in particular cats infect in a very residual way and there is no evidence of transmission of the virus to humans. This is a case of reverse zoonosis, in which cats are the collateral victims without the virus causing them any health problems," says Júlia Vergara-Alert, researcher at IRTA-CReSA. So far, there has only been one episode reported in the Netherlands in which a farmer has been infected through minks, which would be the first known potential case of COVID-19 zoonosis.