Epidemiological investigation of covert mortality nodavirus (CMNV) infection in aquaculture animals in China from 2023 to 2024

Covert mortality nodavirus (CMNV) can infect both aquaculture animals and humans, posing a significant threat to the global biosecurity. Despite its escalating emergence in recent years, comprehensive data regarding the transmission dynamics of CMNV remain limited in aquaculture industry. This study investigated the prevalence and transmission patterns of CMNV in aquaculture populations using molecular, histopathological, and ultrastructural assays. Between 2023 and 2024, a total of 1612 samples were collected from aquaculture provinces in China to elucidate CMNV epidemiology and inform evidence-based control strategies. TaqMan RT-qPCR analysis detected CMNV in various farmed crustaceans, including P. vannamei , M. rosenbergii , P. japonicus , P. monodon , and P. chinensis. Among the collected shrimp samples, the CMNV positive rates were 25.8% (199/772) in 2023 and 29.6% (175/591) in 2024. In situ hybridization confirmed CMNV infection in P. japonicus and P. monodon while transmission electron microscopy verified the presence of CMNV-like particles in necrosis tissues of TaqMan RT-qPCR-positive specimens. These results demonstrated a high prevalence of CMNV in farmed crustacean across China’s coastal farming regions, highlighting the persistent impact of this emerging pathogen. These findings provide critical epidemiological data and a scientific framework for developing targeted disease prevention and management strategies of biosecurity.