| Summary: | In this study, the
humoral immune responses and host protection of rainbow trout, O. mykiss (Walbaum, 1792) against
Ichthyophthirius multifiliis (Ich)
were determined after vaccination with live theronts, sonicated trophonts,
adjuvant added heat inactived theronts. Immunizations with live theronts,
sonicated trophonts or adjuvant added heat inactive theronts by intraperitoneal
(I.P.) injection. Serum immobilization titres were determined 21 days
post-immunization. Four weeks after immunization, the number of trophonts were assessed in rainbow
trout skin four days after challenge. Mean of serum immobilization titres
levels were significantly higher (P<0.05) in fish immunized with live
theronts (1/67,4) and sonicated trophonts (1/29,7) by I.P. injection, than in
the fish immunized with adjuvant added heat inactivated theronts (1/11,4) and
PBS (1/9,42) by I.P. injection. Mean number of the trophonts that can
penetrated to skins were significantly lower (P<0.05) in fish administered
live theronts (21 trophonts/fish) and sonicated trophonts (29,13 tr/fish) by
i.p. injection, than in the fish immunized with adjuvant added heat inactivated
theronts (48,53 tr/fish) and PBS (54,07 tr/fish) by I.P. injection. Therefore, partial
protection was noted on those fish. There was found positive correlation
between higher levels of immobilization titres and partial protection in the
immunized fish.
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