The emerging landscape of feline coronavirus type II in Asia: A review of molecular diversity and diagnostic challenges

Feline infectious peritonitis (FIP) is a fatal systemic disease of cats caused by feline coronavirus (FCoV). FCoV is classified into two biotypes: feline enteric coronavirus (FECV) and feline infectious peritonitis virus (FIPV). In addition, FCoV comprises two serotypes, type I and type II, which are distinguished based on antigenic and genetic differences in the spike (S) protein. Globally, type I is more prevalent than type II. Despite the lower prevalence of type II, its distinct molecular characteristics, including recombination breakpoints within the S gene and variations in accessory genes such as 3c, indicate differences in viral evolution, cellular entry mechanisms, and replication efficiency.This review aims to summarize current knowledge on the molecular characteristics, epidemiology, pathogenesis, and diagnostic aspects of FIP type I and type II, with particular emphasis on data from Asian countries. The findings indicate that type I is the predominant serotype in Asia, whereas type II is detected at considerably lower frequencies.