Detection and semi-quantification of antibodies to the feline infectious peritonitis virus in cats from the Ilhéus-Itabuna microregion, Bahia, Brazil

Abstract

Feline coronavirus (FCoV) is an important virus that can be differentiated into two serotypes: feline enteric coronavirus (FECoV) and feline infectious peritonitis (FIP) virus (FIPV). Researchers have suggested that a mutation of FECoV to FIPV leads to the emergence of FIP, a disease with worldwide distribution and a high mortality rate. Furthermore, in December 2019, a human infectious disease, coronavirus disease-2019 (COVID-19), which is also caused by a coronavirus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) emerged, and clarity regarding its relationship with FCoV remains lacking. Studies have shown that cats are susceptible to infection with this novel coronavirus (i.e., SARS-CoV-2). The aim of the present study was to detect and semi-quantify the presence of feline antibodies to FIPV in cats examined at the Veterinary Hospital of Santa Cruz State University, microregion of Ilhéus and Itabuna, Bahia, Brazil, between January and April 2018. Blood samples were collected from 68 domestic cats to perform complete blood count (CBC) and biochemical tests, and an indirect fluorescent antibody test (IFAT) was used to detect FCoV infection. Of the 68 samples evaluated, seropositivity was observed in 4.4% (3/68) at titers of 1:20; only one sample remained seropositive at titers of 1:40 and 1:80. Two positive animals exhibited CBC and biochemical values within the normal range, while the other positive animals exhibited a mild decrease in platelet count (173,000 uL-1), mild lymphocytosis (7395 uL-1), and mildly increased alkaline phosphatase level (134 uL-1). Twelve months after the tests, none of the positive animals exhibited clinical signs consistent with FIP. Although the IFAT can facilitate diagnosis of FPIV, it cannot be used to differentiate antibodies for the FECoV and FIPV serotypes. Results of the present study demonstrated that FCoV was present in the population studied, and is an important risk factor for the development of FIP. In addition, the new COVID-19 pandemic highlights the importance of studies investigating FCoV because it was not possible to rule out, until now, the possibility of FCoV mutations in infected cats if it encounters SARS-CoV-2.