Contribution of food deprivation to the immune response in rainbow trout ( <i>Oncorhynchus mykiss</i> ) vaccinated against <i>Cryptobia salmositica</i> and <i>Aeromonas salmonicida</i>
2008
Nourollahi-Fard, Saeid Reza
The aims of the present study were to determine (a) the effectiveness of an attenuated live <i>Cryptobia salmositica</i> vaccine; (b) the effects of food deprivation on the immune response and its duration in rainbow trout (<i>Oncorhynchus mykiss</i>) immunised with a live <i>C. salmositica</i> vaccine or with a killed <i>Aeromonas salmonicida</i> vaccine. The fish were divided into three groups (I, II and III; 14 fish per group), those in Groups I and II were under food deprivation (0.40% of body weight), while Group III fish were fed to satiety. The study showed that the attenuated strain of <i>C. salmositica</i> did not cause anaemia and disease, and the fish were protected from clinical disease when they were challenged with virulent parasites. Parasitaemia in all fish vaccinated and challenged with virulent <i>C. salmositica</i> fluctuated and was relatively low; however, fish in Group III had higher parasitaemia than those in Groups I and II between weeks 8 and 14. The numbers of activated neutrophils increased [nitroblue tetrazolium (NBT) assay] after immunisation with both <i>Cryptobia</i> and <i>Aeromonas</i> vaccines and they remained high throughout the experiment. Antibody production (ELISA values) increased after vaccination and were slightly higher in Group III. ELISA titres against <i>A. salmonicida</i> increased after vaccination and decreased after 5 weeks. The titres increased again after the vaccinated fish were given booster, and they were higher than those in the first vaccinated fish.
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