Potential Role of Different Fish Species as Vectors of Koi Herpesvirus (CyHV-3) Infection

Introduction: Koi herpesvirus (KHV) has infected farmed common carp in Poland clinically and asymptomatically since 2004.The role of non-carp species as vectors of virus transmission is well known except for in the case of KHV. The aim was to betterunderstand this virus’ infection and transmission pathways in common carp, looking at the potential vector role of fishes keptwith them. Material and Methods: Eight species were experimentally infected with KHV by immersion in a suspension at 20°C±1 and transferred to a tank after 45 minutes. Specimens were euthanised at intervals up to 56 days post infection (dpi) and tissuewas examined for KHV DNA. Surviving infected fishes were introduced at intervals, each time into a separate tank, to naïvecommon carp for experimental infection. These were observed daily for symptoms, sacrificed along with controls after threemonths, and dissected to provide tissue samples. Also fish from 14 species collected from a farm with a history of KHV weresampled from 3 to 22 months after disease was confirmed. Organ sections from single fish were collected in a single tube.Results: Viral DNA was detected in tench and roach samples up to 49 dpi, but in three-spined stickleback and stone marokosamples only up to 14 dpi. Transmission of KHV to naïve carp occurred after cohabitation. KHV DNA was detected in three fishspecies three months after the farm outbreak. Conclusion: We confirmed that grass and Prussian carp, tench, roach, and brownbullhead can transfer the virus to naïve common carp