Abstract. Herpesvirus cyprini (CHV) genome was traced in carp, Cyprinus carpio L., after acute infection by the method of in situ hybridization with biotinylated probes. The viral genome was detected in several tissues including cranial nerve ganglia. Subcutaneous tissue and spinal nerves. However, at this stage, viral antigens were not detected and the virus was not isolated. The viral genome was also detected in the same fish tissues when papillomas were present which contained viral antigens and even infective virus particles. After papilloma regression, the viral genome was still detected in these tissues. It is suggested that CHV becomes latently established in cranial nerve ganglia, subcutaneous tissue and spinal nerves, and is associated with the induction and recurrence of papillomas.

Effects of thermal conditions on CHV infection were investigated both in vitro and in vivo. CHV multiplied in FHM cells at incubation temperatures from 10•Ž to 25•Ž, but not at 30•Ž, optimal temperature being 15-20•Ž. Experimental infection of CHV was done on carp fry under controlled water temperatures of 15, 20 and 25•Ž. The mortality of carp fry due to CHV infection was markedly high at