Potential application of a small molecule compound in aquaculture against WSSV infection by maintaining the homeostasis of intestinal microbiota

Disease outbreaks consistently lead to substantial economic losses in crustacean farming due to the absence of appropriate treatments for infections caused by the white spot syndrome virus (WSSV). This study focused on examining the in vivo antiviral effects of 2-amino-4-(4-chlorophenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene- 3-carbonitrile (C7) as well as its impact on the intestinal microbiota of shrimp infected with WSSV. The findings demonstrated that C7 at a dosage of 50 mg/kg markedly suppressed WSSV replication in adult shrimp, achieving a maximum inhibitory rate exceeding 90%. Furthermore, C7 effectively inhibited the horizontal transmission of WSSV. From a histopathological perspective, C7 demonstrated the ability to mitigate the damage caused by WSSV to intestinal tissues, preserving the integrity of both the intestinal wall and villi. Infections with WSSV led to a reduction in the abundance of Firmicutes and an elevation in Proteobacteria levels. At the genus level, certain beneficial bacterial groups, including Muribaculaceae and Colidextribacter, exhibited diminished abundance, whereas the presence of opportunistic bacteria such as Shiwanella and Vibrio increased in response to WSSV infection. Following treatment with C7, the abundance of beneficial bacteria increased, harmful bacteria decreased, and the structure of the bacterial community was restored to a normalized state. PICRUSt analysis revealed that the modified microbiota due to WSSV primarily pertained to cellular processes and metabolism, implying heightened activity of gut microbes in afflicted shrimp. In contrast, C7 exhibited the capacity to restore the functionality of the gut microbiota in diseased shrimp. In summary, C7 potentially combats WSSV infection by preserving intestinal tract morphology and upholding a typical flora structure. This groundwork supports the potential application of C7 as a specialized antiviral treatment in aquaculture.