RAPID DIAGNOSIS OF RED-SEA BREAM IRIDOVIRUS INFECTION USING THE POLYMERASE-CHAIN-REACTION

A simple and sensitive polymerase chain reaction (PCR) based assay is described for detection of the red sea bream iridovirus (RSIV) in infe cted fish. The assay involves amplification of a portion of the ribonu cleotide reductase small subunit (RNRS) gene of the virus from DNA iso lated from the spleen. The system was tested on red sea bream followin g an experimental infection. In our infection model, disease signs fir st became apparent 5 to 6 d post-infection, and mortality commenced at Day 6 and reached 90% by Day 9. No amplified product was detected fro m fish at 1 or 2 d postinfection, but 3 of 5 fish tested positive at D ay 3, and all fish tested positive at Days 5 and 8. Thus, infection co uld be detected prior to the appearance of overt symptoms. This PCR me thod should be of considerable value for aquaculture to detect RSIV in fection.