Genetic analysis of feline calicivirus (FCV) isolates associated with a hemorrhagic-like disease

Feline Calicivirus (FCV) is one of the most common causes of upper respiratory tract disease in cats. Other disease syndromes associated with FCV infection have been reported. Recently, calicivirus infections associated with a hemorrhagic-like disease leading to significant mortality in cats has been reported. The clinical signs are similar to those observed with the Calicivirus of Rabbit Hemorrhagic Disease. This investigation characterized two FCV isolates associated with hemorrhagic-like disease. Nucleotide sequencing of the complete genome was done on these two isolates and four isolates representing other disease syndromes. Previously reported sequence data for the entire genome of classical FCV (six isolates) and a portion of the capsid gene for hemorrhagic-like FCV (three isolates) were used in the genetic analysis. Sequence data were used to determine relationships among the isolates and any correlates with phenotype. Nucleotide sequence comparisons of the entire genome and individual ORF's revealed high homology among all isolates. However, data from this study suggest that the virulence may have genetic determinants as revealed by phylogenetic clustering based on a specific 75 nucleotides stretch from the capsid protein gene of the isolates associated with hemorrhagic-like disease.