Short communication A challenge model for Tenacibaculum maritimum infection in turbot, Scophthalmus maximus (L.) R AvendaÇo-Herrera, A E Toranzo and B MagariÇos Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Biologı ´a e Instituto de Acuicultura, Universidad de Santiago, Santiago de Compostela, Spain Keywords: challenge model, immersion, pathogen- icity, Scophthalmus maximus, serotypes, Tenaciba- culum maritimum. Tenacibaculum maritimum (formerly Flexibacter maritimus) is the causative agent of marine tenac- ibaculosis with a worldwide distribution (Ave- ndan ˜o-Herrera, Nu ´n ˜ez, Magarin ˜os & Toranzo 2004a; Avendan ˜o-Herrera, Magarin ˜os, Morin ˜igo, Romalde & Toranzo 2005). This is a major pathogen in the commercial production of turbot, Scophthalmus maximus (L.), causing serious mor- talities and severe economic losses in aquaculture in North-West Spain (Toranzo, Romalde, Dopazo, Magarin ˜os & Barja 2004). A specific turbot vaccine has been developed as a preventive management tool for this disease, and shows the highest protection (more than 85%) when administered by injection (Toranzo, Magarin ˜os & Romalde 2005). However, antimicrobial therapy is still necessary for the control of clinical cases, especially on turbot farms in which vaccines are not used. Despite the significance of T. maritimum in aquaculture, relatively little is known about its pathogenicity and no reproducible challenge model has been developed, preventing a good understand- ing of the route of infection of this pathogen. Pathogenicity studies performed in commercial fish species show that mortalities vary widely according to the different methods used to infect each marine fish species, including red sea bream, Pagrus major (Temminck & Schlegel), black sea bream, Acantho- pagrus schlegeli (Bleeker), sea bass, Dicentrarchus labrax (L.), Atlantic salmon, Salmo salar L., rain- bow trout, Oncorhynchus mykiss (Walbaum), green- back flounder, Rhombosolea tapirin ˜a (Gunther), and striped trumpeter, Latris lineata (Forster) (Waka- bayashi, Hikida & Masumura 1984; Baxa, Kawai & Kusuda 1987; Bernardet, Kerouault & Michel 1994; Soltani, Munday & Burke 1996; Powell, Carson & van Gelderen 2004; Powell, Harris, Carson & Hill 2005). In turbot, Alsina & Blanch (1993) noted that the disease was not induced when bacteria isolated from a severe tenacibaculosis outbreak were administered by intraperitoneal or intramuscular injection. To our knowledge, no immersion challenge experiments with this bacter- ium have been previously performed in turbot. In this study, we describe an effective and reproducible immersion model for tenacibaculosis infection in turbot; this model may be very important in future epidemiological studies and for developing field systems to prevent and/or control tenacibaculosis outbreaks. We have also attempted to determine whether T. maritimum strains belonging to the different serotypes of this bacterium are potentially pathogenic to turbot. Three T. maritimum strains isolated from sole, Solea senegalensis Kaup (PC503.1 and ACC6.1), and turbot (PC424.1) were selected (Table 1), repre- senting the main serotypes described for this pathogen. Briefly, the majority of T. maritimum isolated from sole in NW Spain and all gilthead sea Journal of Fish Diseases 2006, 29, 371–374 Correspondence B Magarin ˜ os, Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Biologı ´a e Instituto de Acuicultura, Universidad de Santiago, 15782 Santiago de Compostela, Spain (e-mail: mpbeam@usc.es) 371 Ó 2006 Blackwell Publishing Ltd