Identification of new genogroups in Austrian carp edema virus isolates

Carp edema virus disease (CEVD), also known as koi sleepy disease (KSD), is an emerging viral disease caused by the carp edema virus (CEV). It is characterized by lethargic behavior, gill necrosis, and generalized edema, leading to significant morbidity and mortality in common carp and koi Cyprinus carpio. Accurate diagnosis of CEVD relies on amplification of a P4a protein-encoding DNA segment from the CEV genome. A phylogenetic analysis of amplified fragments revealed 3 distinct CEV genogroups: I, IIa, and IIb. We explored the phylogenetic relationship between Austrian CEV isolates with existing CEV genogroups. The phylogenetic analysis (n = 18) established the presence of the 3 extant CEV genogroups as well as 2 new CEV genogroups (IIIa and IIIb) classified to identify the Austrian isolates that were distinct from the existing CEV genogroups. It is evident that CEV infection cases are growing in number each year, which may be due to development of sensitive diagnostic assays, while information regarding the virus is scarce. National and international efforts are required to study the epidemiology of the CEV in major carp-producing countries.