Feline coronavirus is common in domestic cats worldwide, and while most infected animals show no symptoms, viral mutations in a subset of cases can trigger feline infectious peritonitis, a fatal systemic disease that appears in either effusive or non-effusive forms. Two substitutions in the viral spike gene, M1058L and S1060A, have been proposed as possible markers of systemic viral dissemination in feline infectious peritonitis, but their diagnostic significance remains debated. A new open-access study in BMC Veterinary Research, published 24 October 2026, reports the detection of feline coronavirus RNA in blood, effusion, and combined blood-effusion samples from cats suspected of having the disease, along with phylogenetic and mutational analysis of a partial spike gene fragment from Iranian isolates.
The research team, led by Viana Javaheri Nasr with colleagues including Naser Sadri, Shahram Jamshidi, Iradj Ashrafi Tamai and Hesameddin Akbarein, collected a total of 100 samples from cats suspected of feline infectious peritonitis: 40 blood samples, 40 effusion samples, and 20 combined blood-effusion samples. All samples were examined by RT-PCR to screen for the feline coronavirus genome. The screening proceeded in two steps. First, PCR was performed targeting the 3′ untranslated region of the viral genome to detect feline coronavirus. Second, a nested PCR was used to amplify a partial spike gene fragment for mutation screening, and a phylogenetic tree was constructed with MEGA 11 using the neighbor joining method.
The results showed that feline coronavirus RNA was frequently detected across the sample types. Of the 100 samples, 13 blood samples (33 percent), 31 effusion samples (78 percent), and 12 combined blood-effusion samples (60 percent) tested positive for the viral RNA genome. Detection rates differed across sample types, with effusion samples showing the highest rate (78 percent), followed by combined blood-effusion samples (60 percent) and blood samples (33 percent).
Phylogenetic analysis of the partial spike gene placed all sequenced Iranian isolates within type I feline coronavirus.
The mutation screening focused on the two spike gene positions most often discussed in connection with feline infectious peritonitis. Among the 10 sequenced isolates, the M1058L substitution was detected in three samples. No substitution was found at position 1060, meaning the S1060A change was absent from every Iranian isolate sequenced in the study.
The authors are careful about what these findings do and do not establish. Because the study did not include confirmed feline infectious peritonitis cases, non-FIP feline coronavirus positive cats, or healthy comparison groups, the results cannot show an association between the spike gene substitutions and the disease, nor can they demonstrate any diagnostic utility for these markers. The study’s conclusions state that further comparative studies are needed to clarify the role of M1058L and S1060A in the transition from common feline coronavirus infection to the fatal systemic form.
The study’s highlights summarize the three main findings: 33 percent of blood, 78 percent of effusion, and 60 percent of combined blood-effusion samples from cats with suspected feline infectious peritonitis tested positive for the virus; Iranian isolates were classified as type I feline coronavirus clustering with viruses from China and the Netherlands; and the M1058L substitution appeared in 3 of 10 sequenced isolates from FIP-suspected cats while no substitution was found at position 1060.
The M1058L and S1060A changes have been proposed in earlier literature as possible indicators of systemic dissemination, but the debate over their reliability as diagnostic markers is precisely what motivated this mutation screen among Iranian isolates.
As an observational study of samples from suspected cases, the work documents the genetic characteristics of circulating feline coronaviruses in Iranian domestic cats and the frequency of viral RNA detection across specimen types. It does not report efficacy of any intervention, nor does it measure disease outcomes. Its contribution lies in the phylogenetic placement of local isolates as type I viruses related to strains from Asia and Europe, and in the observation that the S1060A substitution, at least in this small set of sequenced isolates, was not present, while M1058L appeared in a minority of sequences. Comparative studies with confirmed disease status and control groups will be required to determine whether these spike gene markers hold any value for identifying cats at risk of feline infectious peritonitis.
Subject of Research: Phylogenetic and mutational analysis of feline coronavirus spike gene sequences from domestic cats in Iran
Article Title: Phylogenetic and mutational analysis of the feline coronavirus spike gene in Iranian domestic cats
Article References: Nasr, V. J., Sadri, N., Jamshidi, S., Tamai, I. A., & Akbarein, H. (2026). Phylogenetic and mutational analysis of the feline coronavirus spike gene in Iranian domestic cats. BMC Veterinary Research. https://doi.org/10.1186/s12917-026-06041-2
Image Credits: AI Generated
DOI: 10.1186/s12917-026-06041-2
Keywords: feline coronavirus, feline infectious peritonitis, spike gene, M1058L, S1060A, type I FCoV, phylogenetics, RT-PCR, Iran, domestic cats, nested PCR, viral mutations
News Source: William Thompson. (October 29, 2026). Iranian Cat Coronavirus Isolates Are Type I, Spike Mutation Study Finds. Scienmag.
