Influence of environmental temperature on experimental infection of redfin perch (Perca fluviatilis) and rainbow trout (Oncorhynchus mykiss) with epizootic haematopoietic necrosis virus, an Australian iridovirus.

Experimental transmission of epizootic haematopoietic necrosis virus (EHNV) to adult redfin perch Perca fluviatilis and juvenile rainbow trout Oncorhynchus mykiss was undertaken at different water temperatures using intraperitoneal (IP) and bath inoculation. Redfin perch were highly susceptible to EHNV by both routes of infection. Bath inoculation with as few as 0.08 TCID50.mL-1 was lethal. The incubation period in redfin perch was about 11 days at a water temperature of 19-21 degrees C but was longer at colder temperatures and disease did not occur at temperatures below 12 degrees C. The longest incubation period recorded in redfin perch was 28 days. Rainbow trout were not susceptible to infection by bath inoculation but the disease was reproduced after IP inoculation with 10(5.6) TCID50 at water temperatures ranging from 8-21 degrees C. The incubation period was 3-10 days at 19-21 degrees C, but was up to 32 days at 8-10 degrees C. Persistent infection with EHNV was detected by virus isolation in a clinically unaffected rainbow trout after 63 days. The implications of these findings in the understanding of the epidemiology of EHNV infection are discussed.