Aichivirus A Infection Associated with Severe Enteric and Respiratory Disease in a Captive White Lion (Panthera leo)

Kobuviruses are emerging enteric pathogens with broad host ranges, yet their pathogenic potential in wild large felids remains largely unexplored. Here, we report the first case of severe enteric and respiratory disease associated with AiV-A infection in a large felid, designated FeKoV0813, in a captive juvenile white lion (Panthera leo). The animal presented with acute respiratory distress and severe diarrhea, culminating in death despite supportive care. Comprehensive diagnostic workflows, including necropsy, histopathology, fluorescence in situ hybridization (FISH), and absolute quantitative RT-PCR, were employed to determine tissue tropism and viral dissemination. Whole-genome sequencing, phylogenetic analysis, and selection pressure assessment were conducted to characterize the viral evolutionary dynamics and host-specific constraints. The 8213-nucleotide genome exhibited typical Kobuvirus organization, clustering within the AiV-A clade alongside carnivore-derived strains from dogs, cats, and foxes. High viral RNA loads were detected primarily in the small intestine (~7.4 log10 copies/100 ng RNA) and trachea, with dissemination to the kidney and pancreas. Histopathological analysis revealed epithelial lesions, and FISH localized viral RNA to these affected epithelial cells, while transcriptomic profiling revealed higher transcript abundance of CXCL8 and other pro-inflammatory genes in the intestine than in other tissues. Notably, selection pressure analysis indicated strong purifying selection acting on the feline VP1 gene, with no positively selected sites identified, contrasting with signatures of episodic positive selection observed in human and rodent lineages. This study provides the first report of severe respiratory and gastrointestinal disease associated with AiV-A infection in large felids, significantly expanding the known host range of kobuviruses. Our findings underscore the need for vigilant surveillance of kobuviruses in captive wildlife and highlight the potential risk of spillover infections from domestic carnivore reservoirs.