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Objectives The objectives of this study were to determine the prevalence of feline coronavirus (FCoV) viremia, and its replication in peripheral blood using quantitative RT-PCR (qRT-PCR) methodology in a population of 205 healthy shelter cats in Southern California, as well as to assess any possible connection to longitudinal development of feline infectious peritonitis (FIP). Methods The study was performed on buffy-coat samples from EDTA-anticoagulated whole blood samples of 205 healthy shelter cats. From 50 of these cats, fecal samples were also examined. FCoV genomic and subgenomic RNA in the buffy coats was amplified by a total FCoV RNA qRT-PCR. Evidence for FCoV replication in peripheral blood and feces was obtained by M gene mRNA qRT-PCR. Results Nine of 205 cats (4.4%) were viremic by the total FCoV RNA qRT-PCR, and one of these cats had evidence of peripheral FCoV blood replication by an FCoV mRNA qRT-PCR. The single cat with peripheral blood replication had a unique partial M gene sequence distinct from positive controls and previously published FCoV sequences. Neither seven of the nine viremic cats with follow-up nor the single cat with replicating FCoV with positive qRT-PCR results developed signs compatible with FIP within 6 months of sample collection. Conclusions and relevance FCoV viremia and peripheral blood replication in healthy shelter cats have a low prevalence and do not correlate with later development of FIP in this study population, but larger case-control studies evaluating the prognostic accuracy of the qRT-PCR assays are needed.

A 1.78 kb sequence, including the E, M, 5a and 5b genes, and the intergenic region between the M and 5a genes, of six US strains of infectious bronchitis (corona)virus (IBV) were sequenced and compared to the published sequences for two additional strains. The overall identities as determined through pairwise analyses of nucleotide sequences of the entire 1.78kb region ranged from 90 to 99%, with the 5b open reading frame (ORF) having the greatest identity (94-99%) while the identities of the E, 5a and M ORFs ranged from 87 to 100%. Nucleotide sequencing of recent field isolates from Alabama (Ala1) and California (Cal3) revealed distinct shifts in homology in the M gene, indicating two apparent recombination events between the Holland 52/Mass41-like strain and an Ark-like strain, both origins of commonly used vaccine strains. Putative sites of recombination could also be identified in both the E and M ORFs of laboratory strains of IBV.