Anguillid herpesvirus 1 (AngHV-1) is a pathogen that causes hemorrhagic disease in various farmed and wild freshwater eel species, resulting in significant economic losses. Although AngHV-1 has been detected in the American eel (Anguilla rostrata), its pathogenicity has not been well characterized. In this study, an AngHV-1 isolate, tentatively named AngHV-1-FC, was isolated from diseased American eels with similar symptoms as those observed in AngHV-1-infected European eels and Japanese eels. AngHV-1-FC induced severe cytopathic effects in the European eel spleen cell line (EES), and numerous concentric circular virions were observed in the infected EES cells by transmission electron microscopy. Moreover, AngHV-1-FC caused the same symptoms as the naturally diseased European eels and Japanese eels through experimental infection, resulting in a 100% morbidity rate and 13.3% mortality rate. The whole genome sequence analyses showed that the average nucleotide identity value between AngHV-1-FC and other AngHV-1 isolates ranged from 99.28% to 99.55%. However, phylogenetic analysis revealed that there was a genetic divergence between AngHV-1-FC and other AngHV-1 isolates, suggesting that AngHV-1-FC was a new isolate of AngHV-1. Thus, our results indicated that AngHV-1-FC can infect farmed American eels, with a high pathogenicity, providing new knowledge in regard to the prevalence and prevention of AngHV-1.

The stipe of Hypsizygus marmoreus is a low-value byproduct generated during mushroom processing. Reutilization of this agricultural waste as a functional feed additive may provide both economic and environmental benefits for sustainable aquaculture. This study evaluated the effects of dietary H. marmoreus stipe (HMS) supplementation on the growth performance and survival of juvenile Micropterus salmoides and explored the underlying metabolic and transcriptional responses. Juvenile largemouth bass (initial body weight: 1.13 ± 0.05 g) were fed diets containing 0% (HMS0), 5% (HMS5), or 10% (HMS10) HMS for 46 days. HMS supplementation did not significantly affect growth performance but significantly increased survival rate in both HMS5 and HMS10 groups. Widely targeted metabolomic profiling suggested that dietary HMS may drive prominent shifts in the hepatic and gastric metabolic profiles, with potential changes observed in pathways associated with pyrimidine metabolism, glycerophospholipid metabolism, and ABC transporters. Hepatic transcriptomic analysis further identified differentially expressed genes enriched in these pathways. Integrated multi-omics analysis indicated potential coordinated associations between key metabolites, including orotic acid, ureidosuccinic acid, LPG (16:1), and Val-Cys, and genes involved in nucleotide metabolism, lipid metabolism, and transporter functions, such as DPYD (dihydropyrimidine dehydrogenase), NDK (nucleoside diphosphate kinase), ENTP5 (ectonucleoside triphosphate diphosphohydrolase 5), NT5D2 (5′-nucleotidase domain containing 2), GPT3L (glycerol-3-phosphate acyltransferase-like), ABCA1 (ATP-binding cassette subfamily A member 1), and ABCD4 (ATP-binding cassette subfamily D member 4). In addition, antioxidant enzyme activities were significantly enhanced in the HMS5 group, whereas no further improvement was observed at the 10% supplementation level. Collectively, these findings suggest that dietary HMS supplementation may enhance the survival of largemouth bass via coordinated metabolic regulation and antioxidant responses. This study highlights the potential application of mushroom-processing byproducts as sustainable functional feed ingredients in aquaculture.