IMMUNOCOMPETENCE AND DURATION OF IMMUNITY AGAINST VIBRIO-SALMONICIDA AND AEROMONAS-SALMONICIDA AFTER VACCINATION OF ATLANTIC SALMON (SALMO-SALAR L) AT LOW AND HIGH-TEMPERATURES

The influence of the environmental temperature or, immunocompetence an d duration of immunity in Atlantic salmon was investigated. Immunity a nd antibody responses in fish acclimated and reared at 2 and 10 degree s C were examined 9, 18 and 27 weeks after vaccination with aqueous an d oil-emulsified vaccines. The results obtained show that both aqueous and oil-emulsified vaccines gave full protection against Vibrio salmo nicida independent of the rearing temperature. Vaccination against fur unculosis served to confirm this result. However, the antibody respons e was delayed or strongly suppressed by low temperature (2 degrees C). These results show that immunity can be fully established at temperat ures shown to be non-permissible for specific antibody responses in At lantic salmon. Duration of immunity appears to be strongly correlated to temperature and vaccine formulation. Protection obtained with the a cueous vaccine was severely reduced by 18 weeks after vaccination in f ish reared at 10 degrees C. This negative effect of high rearing tempe rature on the duration of protection was fully prevented by the oil em ulsification of the vaccine antigens. However, high temperature had no similar effect on the duration of antibody production. This may indic ate that duration of antibody production and immunity is not maintaine d by the same mechanisms. (C) 1997 Academic Press Limited.