Dynamic shifts in gut microbiota composition of cats following oral infection with the virulent FIPV strain rQS-79 and treatment with GS-441524.

Feline infectious peritonitis (FIP) is a fatal disease caused by a mutant strain of feline coronavirus (FCoV), and its progression is closely related to gut microbiota and immune response. This study aimed to investigate the changes in the fecal microbiota composition of cats experimentally infected with FIPV, with and without antiviral treatment. Fifteen healthy cats were orally inoculated with the rQS-79 FIPV strain and treated with the antiviral drug GS-441524. Fecal samples were analyzed using 16S rRNA-based next-generation sequencing to assess the microbial diversity and composition. These findings demonstrated that FIPV infection and its treatment led to changes in the quantity and structure of the gut microbiota at the phylum and species levels. Although no significant taxa were linked to a specific group, Firmicutes was the predominant phylum, followed by Actinobacteria and Bacteroidota. Infected cats showed decreased levels of beneficial bacteria, such as Bifidobacterium and Lactobacillus (p < 0.05), along with increased levels of pathogenic Clostridium and Escherichia. Treatment with GS-441524 reduced the abundance of certain pathogenic (Peptoclostridium spp.) and beneficial (Bifidobacterium spp.) bacteria in the gut. These findings highlight that both viral infection and antiviral treatment disrupt the gut microbial balance. Thus, an integrated approach combining antiviral drugs, probiotics, and dietary modulation may offer a more effective strategy for restoring microbiota homeostasis and improving the outcomes of FIP and similar viral infections in cats.