Infectivity experiments with Cyprinus carpio iridovirus (CCIV), a virus unassociated with carp gill necrosis

Abstract. Experiments to determine Cyprinus carpio iridovirus (CC1V) virulence to fish of different ages and species were performed; viz. carp, Cyprinus carpio L., goldfish, Carassius auratus (L.), and rainbow trout, Oncorhynchus mykiss (Walbaum). Neither signs of disease nor mortality occurred in any of the fish species tested. Five passages of the virus in carp resulted in its loss and, not surprisingly, there was no enhancement of virulence. In carp inoculated intraperitoncally, the virus persisted for more than 6 weeks at 18-20°C, more than 12 weeks at a water temperature increasing from 10 to 20°C and more than 27 weeks at 6 5-8°C. The fish cleared itself of the virus after more than 6 weeks maintenance at 18-20°C. The viral infectivity via water is very low. It was impossible to infect the fish with the cell culture grown virus either by water immersion or by prolonged cohabitation with experimentally infected fish. From infectivity data, the authors conclude that the investigated iridovirus is not the aetiological agent of carp gill necrosis.