First observation of rickettsia-like organisms in cultured sea bass (Dicentrarchus labrax) in Turkey

Abstract

This paper describes the first observation of rickettsia-like organisms (RLOs) in cultured European sea bass (Dicentrarchus labrax) in Turkey. Generally, fish infected by the organism were anorexic, lethargic and experienced high levels of mortality during disease outbreaks. Internally, most of the affected fish exhibited grey to yellow coloured multifocal nodules in their kidneys and spleens. Although Listonella (Vibrio) anguillarum and Photobacterium damselae subsp. piscicida were isolated from diseased fish, clinical and pathological examination also indicated the presence of RLOs in diseased sea bass. Histopathologically, multifocal necrosis of parenchyma cells of the spleen, liver, kidney skeletal and heart muscle was observed, associated with an inflammatory reaction. Diseased fish also contained what appeared to be RLOs within the cytoplasmic vacuoles of their blood monocytes. The presence of RLOs in tissues of diseased fish was confirmed by immunohistochemistry (IHC).