Emergence and spread of feline infectious peritonitis due to a highly pathogenic canine/feline recombinant coronavirus

Cross-species transmission of coronaviruses (CoVs) poses a serious threat to both animal and human health1-3. Whilst the large RNA genome of CoVs shows relatively low mutation rates, recombination within genera is frequently observed and demonstrated4-7. Companion animals are often overlooked in the transmission cycle of viral diseases; however, the close relationship of feline (FCoV) and canine CoV (CCoV) to human hCoV-229E5,8, as well as their susceptibility to SARS-CoV-29 highlight their importance in potential transmission cycles. Whilst recombination between CCoV and FCoV of a large fragment spanning orf1b to M has been previously described5,10, here we report the emergence of a novel, highly pathogenic FCoV-CCoV recombinant responsible for a rapidly spreading outbreak of feline infectious peritonitis (FIP), originating in Cyprus11. The recombination, spanning spike, shows 97% sequence identity to the pantropic canine coronavirus CB/05. Infection is spreading fast and infecting cats of all ages. Development of FIP appears rapid and likely non-reliant on biotype switch12. High sequence identity of isolates from cats in different districts of the island is strongly supportive of direct transmission. A deletion and several amino acid changes in spike, particularly the receptor binding domain, compared to other FCoV-2s, indicate changes to receptor binding and likely cell tropism.