Efficacy of furunculosis vaccines in turbot, Scophthalmus maximus (L.): evaluation of immersion, oral and injection delivery Y Santos 1 , S García-Marquez 1 , P G Pereira 1 , F Pazos 1 , A Riaza 2 , R Silva 2 , A El Morabit 1 and F M Ubeira 3 1 Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Biologı ´a, Universidad de Santiago, Santiago de Compostela, Spain 2 Stolt Sea Farm, Lira, Spain 3 Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Farmacia, Universidad de Santiago, Santiago de Compostela, Spain Abstract The commercial furunculosis vaccine Aquavac Furovac 5 and an autogenous vaccine, based on the challenge strain, induced immune protection in turbot, Scophthalmus maximus (L.), as shown in challenge tests 120 days post-immunization by injection (relative percentage of survival, RPS ¼ 72–99%). This protective effect lasted for at least 6 months post-immunization at appreciable levels (RPS ¼ 50–52%). Neither the autogenous vaccine nor the commercial vaccine was able to induce significant levels of protection against Aero- monas salmonicida in turbot when administered by immersion. Antibody levels were high or moderate in fish vaccinated by injection with the different vaccines and very low in fish vaccinated by immer- sion. The field results show that delivering an oral boost after the primary vaccination by injection did not enhance protection of turbot against furunculosis and that water-based (autogenous vaccine) and oil adjuvanted (Alpha Ject 1200) vaccines administered by injection conferred similar levels of protection (RPS > 80%) in turbot. Keywords: Aeromonas salmonicida ssp. salmonicida, Alpha Ject 1200, Aquavac Furovac 5, autogenous vaccine, humoral response, vaccination. Introduction Furunculosis caused by Aeromonas salmonicida ssp. salmonicida is one of the most important bacterial diseases affecting cultured and wild salmonid fish throughout the world (Ellis 1997; Austin & Austin 1999). The bacterium has also been isolated as the causative agent of mortalities in valuable non- salmonid marine fish species, such as turbot, Scophthalmus maximus (L.), sea bream, Sparus aurata L., and sea lamprey, Petromyzon marinus L. (Toranzo, Santos, Nu ´n ˜ez & Barja 1991; Toranzo & Barja 1992; El Morabit, Garcı ´a-Ma ´rquez & Santos 2004). The disease, first described in turbot in fish cultured in North-West Spain in 1992 (Toranzo & Barja 1992), is, at present, one of the most threatening problems affecting turbot production in Spain and Portugal. The main external signs of furunculosis in infected fish are haemorrhagic zones at the base of the pectoral fins and mouth and ulcerative lesions on the dorsal and ventral surface (Toranzo & Barja 1992). Taxonomic analysis demonstrated (Toranzo et al. 1991; Toranzo & Barja 1992) biochemical, serological and genetic homogeneity among A. salmonicida strains isolated from turbot and salmonid fish. The control of furunculosis by chemotherapeutic agents is limited due to the rapid development of resistance and the possibility of tissue residues. Therefore, prevention of the disease through the use of vaccines is a desirable alternative. Successful Journal of Fish Diseases 2005, 28, 165–172 Correspondence Y Santos, Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Biologı ´a, Universidad de Santiago, 15782 Santiago de Compostela, Spain (e-mail: mpsantos@usc.es) 165 Ó 2005 Blackwell Publishing Ltd