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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>

Nourollahi-Fard, Saeid Reza
Acta veterinaria Hungarica 2008 v.56 no.2 pp. 197-206
Aeromonas salmonicida, Cryptobia, Oncorhynchus mykiss, anemia, antibody formation, body weight, enzyme-linked immunosorbent assay, fish, food deprivation, neutrophils, nitroblue tetrazolium, parasitemia, parasites, satiety, vaccination, vaccines, virulence
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.