Prevalence, Clinical Signs, Diagnosis and Treatment of Post-Pandemic SARS-CoV-2 Infection in Cats in 2023: Co-Infection with FHV, FCV, Mycoplasma spp. and Chlamydia felis—A Single-Center Study in Bulgaria

SARS-CoV-2 is a zoonotic virus with a proven ability to infect various animal species, including domestic cats. In the post-pandemic period of COVID 19, limited data still exist on the clinical course, shedding of infectious virus and diagnostic features in cats. The aim of this study was to investigate the spread of SARS-CoV-2 in cats in 2023, the clinical manifestations of the infection, the diagnostic algorithm, including molecular detection of viral components, the differential diagnosis of co-infection with FHV, FCV, Mycoplasma spp. and Chlamydia felis, serology, and the isolation of infectious SARS-CoV-2. The immunomodulatory therapy in animals with a standalone SARS-CoV-2 infection was applied. The study included oropharyngeal, conjunctival and nasal swab samples from 102 domestic cats with clinical signs. Of them, 20.6% (21/102) were positive for SARS-CoV-2, with 16.67% (17/102) of the cats showing various variants of co-infection with FHV, FCV, Mycoplasma spp. and Chlamydia felis. Four of the cats had a standalone SARS-CoV-2 with mild clinical manifestations that included serous discharges from the eyes, without change in the general condition. The virus was isolated from these samples. These four cats and their owners were positive for antibodies to the virus, and the owners were PCR-negative. The treatment of SARS-CoV-2 infection included the preparations Viusid, RX immunosuport, Vetomun and Lisymun. This is one of the first post-pandemic studies covering FHV, FCV, Mycoplasma spp. and Chlamydia felis in domestic cats with SARS-CoV-2 infection and further expands on the essential main idea including the specified pathogens of interest.