Molecular Epidemiology and Genetic Diversity of Carp Edema Virus (Cev) in China (2013–2019): New Insights into Transmission and Diagnosis

Abstract

Carp edema virus (CEV), an emerging pathogen, poses a significant threat to global aquaculture, especially in China, the world’s leading producer of carp. This study investigated the molecular epidemiology of carp edema virus (CEV) in China from 2013 to 2019, during which 781 samples across 21 provinces were analyzed via PCR. The results indicated a CEV positivity rate of 9.86%, with the highest prevalence noted in Henan and Jiangsu provinces. Common carp and koi are sensitive to CEV, while grass carp, Prussian carp, and goldfish are resistant, even under coculture conditions. Notably, CEV and KHV coinfections have been reported, and this study documents the first instance of CEV and SVCV coinfection in China. Phylogenetic analysis based on 357 bp sequences of the CEV P4a gene from 83 isolates and 45 reference sequences from GenBank identified 31 sequence types. Most sequences fell within genogroup IIa, suggesting multiple intro- ductions of CEV into China, while a distinct cluster of Henan isolates within genogroup IIb indicated a separate introduction. This study underscores the role of environmental temperatures, ranging from 8°C to 30°C, in the ecological adaptability and infection rates of CEV. The genetic relatedness of Chinese isolates to European strains points to international trade as a possible transmission route. This research advocates for advanced molecular diagnostics to enhance pathogen identification, highlighting the crucial role of systematic surveillance and biosecurity measures in controlling the spread of CEV in aquaculture, a factor that complicates disease management and highlights the need for multi-pathogen surveillance.

Keywords: Carp edema virus, epidemiology, diagnostics, PCR, risk factors