Persistence of Piscirickettsia salmonis and detection of serum antibodies to the bacterium in white seabass Atractoscion nobilis following experimental exposure

KD Arkush, HL Edes, AM McBride, MA Adkison, RP Hedrick
2006 Diseases of Aquatic Organisms  
White seabass Atractoscion nobilis surviving experimental exposure to Piscirickettsia salmonis harbored the bacterium for periods up to at least 123 d post injection (dpi). Intraperitoneal injections of juvenile white seabass with 1.26 × 10 2 TCID 50 P. salmonis fish -1 resulted in a 29% cumulative mortality over a 27 d period. Both molecular and histologic methods provided evidence for persistence of the bacterium in fish sampled sequentially from the surviving population. Throughout the
more » ... of acute mortality, the bacterium was detected in all impression smears of liver tissue stained with Giemsa and was reisolated in cell cultures from all dead fish sampled. Polymerase chain reaction (PCR) assays detected P. salmonis-specific DNA in 13.3 to 50% of the fish sampled at time points between 28 and 123 dpi, while cell culture reisolation was largely ineffective in detecting the bacterium. An enzyme-linked immunosorbent assay (ELISA) detected serum anti-P. salmonis antibodies in 48 of 59 white seabass exposed to P. salmonis but not in fish which were not exposed to the bacterium. At the end of the 4 mo experiment, microscopic lesions consisting of single to multiple and coalescing granulomas were found in liver and kidney tissues of 9 of 10 fish examined from the exposure group, while no lesions were detected in the fish from the control group. Immunohistochemical staining with anti-P. salmonis polyclonal antibodies detected bacterial antigens in some but not all granulomas examined from the exposure group at 4 mo. This study demonstrates that P. salmonis may persist among white seabass following infection and thus provide a potential reservoir of infection contributing to transmission both within and between fish species in the marine environment. KEY WORDS: Piscirickettsia salmonis · White seabass · Persistent infection · Carrier state Resale or republication not permitted without written consent of the publisher Editorial responsibility: David Bruno,
doi:10.3354/dao073131 pmid:17260832 fatcat:a62yl4itkzgqfbzqhtogiyb4qu