Submitted to: Journal of Fish Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/18/2003
Publication Date: 3/1/2004
Citation: Xu, D., Klesius, P.H., Shelby, R.A. 2004. Immune response and host protection of channel catfish, Ictalurus punctatus (Rafinesque) against Ichthyophthirius multifiliis after immunization with live theronts and sonicated trophonts.Journal of Fish Diseases. 27:135-141. Interpretive Summary: This study determined immune responses and host protection of channel catfish against parasite Ichthyophthirius (Ich) after immunization with live theronts and sonicated trophonts. Ichthyophthirius causes high mortalities of fish and leads to heavy economic loss in aquaculture in the tens of million dollars annually. Currently, the control of parasite depends largely on the use of chemicals, but it is not effective after the parasite penetrates into fish skin and gills. Channel catfish immunized with live theronts by both immersion and injection acquired complete protection against Ich. The immunized fish showed higher levels of anti-Ich antibodies in skin and serum than non-immunized fish. No parasite infection and mortality occurred in these fish immunized with live theronts. Fish immunized with sonicated trophonts by injection had a low (10%) infection and mortality compared to the near 100 % infection and mortality in non-immunized fish. The results of this study show the vaccination against Ich is an alternative to chemical treatments since the surviving fish from an Ich infection develop immunity against reinfection by the parasite.
Technical Abstract: This study determined humoral immune responses and host protection of channel catfish Ictalurus punctatus (Rafinesque) against Ichthyophthirius multifiliis (Ich) after immunization with live theronts and sonicated trophonts. Immunizations with live theronts or sonicated trophonts were done by both bath immersion and intraperitoneal (IP) injection. Cutaneous and serum immunoglobulin (Ig) levels and anti-Ich antibodies were measured 12 and 21 days post immunization. The level of Ich infection and survival of catfish were determined after theront challenge. Cutaneous and serum anti-Ich antibodies were significantly higher (p<0.05) in fish immunized with live theronts by immersion and IP injection and with sonicated trophonts by IP injection than in fish immunized with sonicated trophonts by immersion, with bovine serum albumin by IP injection, or non-immunized controls. Host protection was noted only in fish immunized with live theronts by immersion and IP injection and with sonicated trophonts by IP injection. There was a positive correlation between higher levels of anti-Ich antibodies and host survival in the immunized fish. In summary, channel catfish immunized with live theronts by immersion and IP injection and with sonicated trophonts by IP injection acquired protective humoral immune responses against Ich that appears to be related to an antibody response to Ich.