Detection and phylogenetic analysis of carp edema virus in common carp (Cyprinus Carpio) in Iran; 2020–2021

Abstract

Carp edema virus (CEV), a member of the family Poxviridae, is the etiologic agent of carp edema virus disease, also known as the koi sleepy disease (KSD). The disease is important across the world because it increases mortality rates in common carp and koi carp. From autumn 2020 to spring 2021, gills and internal organs were collected from suspected common carps cultured in twenty Iranian farms in Khuzestan, Gilan, and Mazandaran provinces. The presence of CEV was confirmed by molecular diagnosis. PCR was performed using specific primers to amplify the p4a gene, and positive samples were subsequently sequenced. Phylogenetic analysis assigned them to CEV genogroup I, and they shared high nucleotide sequence similarity with CEVs from Italy, Hungary, Iraq, Poland, the United States, and the Czech Republic. The results confirmed the presence of CEV in Iranian freshwater aquaculture after five years of observing clinical symptoms strongly reminiscent of CEV disease. The results also warned of the spread of the virus throughout the continent and point to the need to implement restrictions on the fish trade. Further studies are needed to determine the full-genome sequences of circulating viruses in order to provide insights into the epidemiology of fish viruses in Iran and the region.