Winn’s Cat Health News blog has posted numerous summaries about feline coronavirus (FCoV) infection in cats and its more lethal form, feline infectious peritonitis (FIP). Feline coronavirus infection is very commonly found in cats and their environment, especially the multi-cat setting. Between 5 and 10% of FCoV infections will result in the fatal form, FIP.
Feline coronavirus is a RNA virus that undergoes a high rate of mutation during replication, resulting in clusters of genetically diverse species, or also known as quasispecies. This ability for genetic diversity, along with being able to recombine with other coronavirus strains, is the basis for their pathogenicity and cross-species transmission. There are two recognized serotypes: Type 1, which represents most of the field strains in naturally infected cats, and Type 2, which resulted from recombination between Type 1 FCoV and CCoV (canine coronavirus). It is through the genetic and serological differences in their transmembrane spike (S) gene and protein that creates this differentiating factor. The S protein has been found to be part of the virus that binds to the host receptor, facilitating host cell entry.
There are three major factors contributing to the development of FIP: 1) viral factors – mutations in the fusion peptide sequence of the FCoV S gene and changes in the related furin cleavage site along with other mutations where FCoV develops its tropism for monocyte/macrophage cells and allows for systemic viral spread outside the intestinal tract and leading to development of FIP, 2) host factors – these include the host immune response (such as the significant decrease of T-lymphocytes with FIP), monocyte ability to sustain virus replication, breed and genetics, 3) environmental factors – this includes stress levels and overcrowding in housing that might increase viral replication in individual cats, therefore increasing viral mutations which can lead to FIP development. Part One (VT)
Comment: The summarized article for this series is quite detailed and recommended for reading in full.