Susceptibility of three different strains of juvenile Atlantic halibut (Hippoglossus hippoglossus L.) cultured at two different temperatures to Vibrio anguillarum and temperature effect on antibody response

Abstract

Three geographically distinct-reared strains (Canadian, Icelandic, Norwegian) of juvenile Atlantic halibut (Hippoglossus hippoglossus L.) cultured at optimal and super-optimal growth temperatures (12 and 18° C respectively), were challenged with a virulent isolate of Vibrio anguillarum by injection. The halibut were injected intraperitoneally with 100 μl of the bacterial suspension (1×106 cells per fish). After challenge, temperature and strain-related differences in survival were observed. Canadian and Icelandic halibut cultured at the super-optimal temperature of 18° C were significantly more susceptible to infection than those strains cultured at 12° C. Total mortality at 18° C for the Canadian and Icelandic strains was 56·4 and 61·85% respectively, compared to 32 and 26·6% respectively at 12° C. Norwegian halibut were significantly more resistant to infection with V. anguillarum at 18° C compared to the other strains, with total mortality of 13·3%. There was no significant difference in total mortality of Norwegian halibut at 18 or 12° C (13·3, 25% respectively). The specificity of the antibodies in sera from challenged halibut cultured at 18° C was primarily to LPS. Immunoblots showed the presence of antibodies against O-side chain antigens. This reaction was strongest in sera from the Norwegian halibut strain compared with the Canadian and Icelandic halibut, which suggests that the difference in resistance to challenge may be ascribable to the presence of antibodies to LPS. Specific antibody levels, as measured by ELISA, increased with increasing temperature and strain differences were apparent, however these did not relate to disease resistance.