Koi Herpesvirus Disease: Current knowledge and future perspectives in aquaculture health

Abstract

Koi Herpesvirus Disease (KHVD) is a highly contagious viral disease of common carp (Cyprinus carpio) and koi, caused by Cyprinid herpesvirus 3 (CyHV-3). This disease can cause high mortality, especially in young fish, significantly impacting the global fisheries economy. KHVD is typically characterized by epithelial lesions on the gills, skin ulcerations, kidney damage, and basophilic intranuclear inclusions in epithelial cells, a hallmark of active infection. Clinical symptoms include lethargy, loss of appetite, impaired swimming behavior, gill hyperemia, excessive mucus production, and skin discoloration. Diagnosis of KHVD requires a combination of methods. Clinical and histopathological examinations can provide early indications, while serological and molecular detection methods such as PCR or qPCR are used to confirm acute and latent infections, including in asymptomatic carriers. Key risk factors include fish age, optimal water temperature for the virus (18–28°C), population density, environmental quality, and culture practices. Fish that survive infection can become latent carriers and potentially transmit the virus again, exacerbating the disease outbreak. Controlling KHVD requires an integrated strategy, including biosecurity, quarantine of new fish, management of density and water quality, and vaccination using live attenuated, inactivated, or subunit/DNA vaccines. This strategy aims to suppress virus spread, increase fish survival, and minimize economic losses. A thorough understanding of the pathology, epidemiology, and transmission mechanisms of KHVD is essential for effective and sustainable disease management in carp and koi aquaculture.