Cyprinid herpesvirus 1 (CHV) or Herpesvirus cyprini was virulent for carp, Cyprinus carpio L.. fry following lh immersion in water at 20X. Cumulative mortality for carp fry was 86-97% in 2-week-old eommon carp, 20% in 4-week-oId faney carp, and 0% in both 8week-old common and fancy carp. The virus did not produce mortality in fry of crucian carp, grass carp or other eyprinids. It was also oncogenic in earp. inducing papillomas to the extent of 55% among both common and fancy earp fry. The neoplasms appeared 5-6 months after carp had been exposed to the virus by immersion and reeurred at an ineidenee of 83% in earp 7 5 months post-desquamation of the tumour. The CHV was reisolated from all moribund fish and from all survivors. It also induced papillomas at an incidence of 13% in adult mirror earp and at 10% in adult faney earp 5 months after intraperitoneal inoeulation of lO^TCIDsomr' fish. The virus was reisolated only from the neoplastic tissue and not from internal organs. The neoplasms were normally loeated on fin, skin or mandible, at the intraperitoneal inoeulation site. Spccifie fluoreseenee for CHV antigen was frequently detected in the gills, liver, kidneys and intestine of 2-week-old fry from 3 to 21 days following ehallenge with CHV. It was found in greater eoneentrations in experimentally induced papillomata on 2-week-old carp fry survivors examined 24 weeks after challenge than in naturally occurring neoplasms.

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