DAO 64:107-119 (2005)  -  doi:10.3354/dao064107

Confirmation of Piscirickettsia salmonis as a pathogen in European sea bass Dicentrarchus labrax and phylogenetic comparison with salmonid strains

Ú. McCarthy1, N. A. Steiropoulos2, K. D. Thompson1,*, A. Adams1, A. E. Ellis3, H. W. Ferguson1

1Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK
2Fish Pathology Lab, Aquaculture and Fisheries Dept., Technological Institute of Epirus, Igoumenitsa, Greece
3Fisheries Research Services (FRS) Marine Laboratory, PO Box 101, 375 Victoria Road, Aberdeen AB11 9DB, UK
*Corresponding author. Email:

ABSTRACT: European sea bass Dicentrarchus labrax from the Mediterranean were diagnosed with a severe encephalitis. Rickettsia-like organisms (RLOs) were associated with brain lesions in routine paraffin sections. These were found to share common antigens with the Piscirickettsia salmonis type-strain, LF-89, by indirect fluorescent antibody test (IFAT) and by immunohistochemistry (IHC). In addition, we compared the DNA sequences of the 16S rDNA and 16S-23S internal transcribed spacer region (ITS) with those published for P. salmonis strains and found that the sea bass piscirickettsia-like organism (SBPLO) was another strain of P. salmonis, closely related to the salmonid pathogens. Furthermore, we showed that the SBPLO possessed at least 2 ITS regions, 1 of which contained tRNA genes.


KEY WORDS: Piscirickettsia salmonis · European sea bass Dicentrarchus labrax · IFAT · Immunohistochemistry · rDNA · Phylogeny


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