Deletions in the 7a ORF of feline coronavirus associated with an epidemic of feline infectious peritonitis

A population of Persian cats experienced an epidemic of feline infectious p eritonitis (FIP) over 2 years. Twelve cases of FIP occurred in litters born during this period. Cats contracting FIP were all genetically related thro ugh the sire. Feline coronavirus (FCoV) genomic RNA was detected consistent ly in this study in biologic samples from adult cats, kittens suffering fro m FIP, and their siblings. Analysis of viral 7a/7b open reading frame (ORFs ) were analyzed and revealed two distinct virus variants circulating in the population, one with an intact 7a ORF and one with two major deletions in the 7a ORE The 7b ORFs were intact and similar among all virus isolates, al though point mutations resulting in amino acid changes were present. The si re was determined to be infected with both variants, and was persistently v irus-infected. We speculate the deletion variant arose from the non-deletio n variant during viral replication in this population, possibly in the sire . (C) 2001 Elsevier Science B.V. All rights reserved.