First isolation of koi herpes virus (KHV) in Italy from imported koi (Cyprinus carpio koi)

The present work describes the first Italian koi herpes virus (KHV) outbreak where the infectious agent was isolated and genetically characterized. At the beginning of April 2012, a batch of koi (Cyprinus carpio koi) was imported from Israel by a wholesale facility located in North-Eastern Italy. Fish, originating from different farms, were shipped separately but maintained together in the same tank upon arrival. Three weeks after the introduction of fish, an increased mortality was recorded. Typical clinical and pathological signs of koi herpesvirus disease (KHVD) were observed: enophthalmia, skin erosion, gill hemorrhages and necrosis, pale and enlarged kidney. The histological analysis of symptomatic koi allowed the detection of typical pale intranuclear inclusions in gill epithelium, intestinal lamina propria and kidney. Viral isolation yielded positive results and KHV isolation was confirmed by immunofluorescence. Conventional and real time PCR substantiated the presence of Cyprinid Herpesvirus type 3 (CyHV-3) belonging to the U/I lineage. Mortality in the koi tank reached 82.5% and the few surviving fish were culled by the Official Veterinary Inspector. Epidemiological data and laboratory results suggested that the virus likely originated from Israel.