Abstract
Bacterial coldwater disease is considered to be one of the most serious diseases in ayu Plecoglossus altivelis in Japan. We evaluated the efficacy of three highly water-soluble adjuvants (Montanidae IMS-1311, IMS-1312 and IMS-2212) combined with formalin-killed bacterin of Flavobacterium psychrophilum (FKB) in ayu, in comparison with a minimally water-soluble adjuvant (Montanidae ISA-763A). The retention period and toxicity of these adjuvants in ayu were also examined. Experimental challenge 4 wk after vaccination showed that FKB adjuvanted with IMS-1311 and IMS-1312 had higher potency than FKB alone and significantly (p<0.05) higher potency than the control with sterile distilled water. Residues of the highly water-soluble adjuvants in ayu remained for shorter periods than that of the minimally water-soluble adjuvant, although the former adjuvants were acutely toxic at doses higher than 25μL/fish (1.7±0.5g). The high level of protection, shot retention period and lack of toxicity indicate that a dose of 5μL of IMS-1311 or IMS-1312 combined with 5μL of FKB makes a promising vaccine against bacterial coldwater disease in ayu.
