Winter disease outbreak in sea-bream (Sparus aurata) associated with Pseudomonas anguilliseptica infection

The nature of an outbreak of 'winter disease' affecting both juvenile and adult sea-bream (Sparus aurata) in several Iberian Peninsula farms from January to April of 1996 is described. The average mortality rate was approximately 10-15%, although in some fish farms mortality reached 30%. Pure cultures of aerobic Gram-negative filamentous rods were isolated from the kidney of diseased fish, as well as from some of the liver and ascitic fluid samples. 16S rRNA gene sequence analysis identified the isolates from diseased fish as Pseudomonas anguilliseptica. The results of biochemical and physiological tests of clinical isolates and the type strain of P. anguilliseptica were entirely consistent with the genotypic identification. The isolation of P. anguilliseptica exclusively from the diseased fish of all affected fish farms, together with the failure to isolate this bacterium from non-affected fish of the same farms. suggest that P. anguilliseptica is likely to be the agent responsible for the 'winter disease' outbreak in the sea-bream examined. The relationship of the 'winter disease' outbreaks to stressful environmental conditions is discussed. (C) 1997 Elsevier Science B.V.