High detection rate and genetic diversity of feline caliciviruses in an island population of feral cats with/without oral lesions

Although feline caliciviruses (FCVs) (Family Caliciviridae) have been studied extensively in household and shelter cats, limited information is available on FCVs in feral cat (Felis catus) populations. We report here high FCV detection rates (27.77%, 30/108) in oral samples from feral cats on the Caribbean island of St. Kitts. Fourteen (46.66%) of the FCV positive cats exhibited oral lesions that were characteristic of FCV infection. Based on analysis of VP1 sequences, the FCV strains from St. Kitts (FCP strains) formed two phylogenetically distinct clusters within FCV genotype-I, and exhibited significant genetic diversity between themselves, and with those of other FCVs (including the FCV vaccine strains). We identified genetically distinct FCV variants co-circulating in certain feral cat colonies, and hypothesized multiple-independent introductions of FCVs into the island feline population (especially from North America). Based on analysis of the putative VP1 E region, the FCP strains retained the conserved amino acid (aa) residues that are crucial for FCV binding to host receptor, whilst aa mismatches at the neutralizing and non-neutralizing epitopes, and at the virulence-related aa positions were observed between the FCP strains (and between the FCP strains and FCV vaccine strains). Taken together, our findings highlighted the complex molecular epidemiology of FCVs in the St. Kitts feral cat population, which might facilitate emergence of virulent pathotypes and/or antigenic variants. Considering these observations, and the potential risk of FCV transmission between feral and household cats, large-scale molecular epidemiological studies on FCVs in feral cat populations from different geographical regions are of utmost importance. To our knowledge, this is the first report on molecular prevalence and genetic diversity of FCVs from the Caribbean region.