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Diseases of Aquatic Organisms

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DAO 61:53-57 (2004)  -  doi:10.3354/dao061053

Experimental infection of coho salmon Oncorhynchus kisutch by exposure of skin, gills and intestine with Piscirickettsia salmonis

P. A. Smith*, M. E. Rojas, A. Guajardo, J. Contreras, M. A. Morales, J. Larenas

Department of Animal Pathology, Unit of Pathology of Aquatic Animals, Faculty of Veterinary Sciences, University of Chile, Santiago, Chile

ABSTRACT: Piscirickettsiosis pathogenesis was examined using some tissues as entry portals of Piscirickettsia salmonis in coho salmon. Juvenile fish, weighing approximately 8.4 g, were used in this trial. Inocula were prepared using the strain SLGO-95 of P. salmonis. The micro-organism was cultured in the CHSE-214 cell line as described by Fryer et al. (1990) and doses containing 104.7 and 103.7 TCID50 were prepared. Each dose was used to infect the fish via skin, gills and intestine. Skin and gills were exposed by calibrated drops, and the intestine by an intubation through the anal opening. Some fish were injected intraperitoneally with the same P. salmonis doses, as positive virulence controls. Sham-inoculated fish for each of the tested routes were also included as negative controls. Piscirickettsiosis was experimentally reproduced with all the inoculation methods. Cumulative mortalities and survival analyses showed that the most effective entry portal was skin followed by intestinal intubation and finally by gill infection.

KEY WORDS: Piscirickettsia salmonis · Pathogenesis · Fish disease · Coho salmon

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