Publication Abstract

 

Sea bass were experimentally exposed to RGNNV by intramuscular injection and co-habitation, reaching cumulative morbidity above 75-58 %, at dose 10⁶-10⁵ TCID50/ml respectively in the injected group. Survival fish sampled at 42 days suffered an asymptomatic infection where necrotic cells were observed in brain as well as vacuoles in internal nuclear layer of the retina. Low but significant levels of neutralising antibody were detected in moribund fish as soon as five days post infection and maintenance in survival group up to six weeks; whereas no immune response neither clinical symptoms were detected in co-habitants. In the acute phase of disease, RNA2 viral segment was detected in sera from moribund but not from survival fish; however no virus isolation in cell culture was possible from neither of the sera tested. Immunohistochemistry revealed viral antigen in brain and eye of moribund and survival fish corresponding with histological damage, but also immuno positive cells were detected in several internal organs. In both groups, viral RNA was detected by first round of PCR in nervous tissues and then by nested PCR in all tissues analysed. However infective virus was isolate just from moribund fish group, being the higher viral titre recovered from nervous tissues.