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Title: PROTECTIVE EFFECT OF CUTANEOUS ANTIBODY PRODUCED BY CHANNEL CATFISH IMMUNE TO ICHTHYOPHTHIRIUS ON COHABITED NON-IMMUNE CATFISH

Author
item Xu, Dehai
item Klesius, Phillip

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2003
Publication Date: 5/1/2003
Citation: XU, D., KLESIUS, P.H. PROTECTIVE EFFECT OF CUTANEOUS ANTIBODY PRODUCED BY CHANNEL CATFISH IMMUNE TO ICHTHYOPHTHIRIUS ON COHABITED NON-IMMUNE CATFISH. JOURNAL OF FISH DISEASES. 2003.

Interpretive Summary: Ichthyophthirius multifiliis (Ich) is one of the most severe fish parasites and attacks almost all species of freshwater fish at every growth stages. The Ich infections cause high mortalities and heavy economic loss in both farmed and ornamental fish. Ich infections are difficult to control with chemicals. There is a need for a biological method to control this fish parasite. Fish recovered from Ich infection develop immune response against the parasite. From previous study, we found that cutaneous antibody secreted from Ich immune fish immobilized theronts in vitroand reduced their chance to infect fish. This study evaluated if Ich immune fish secrete antibody into water and protect non-immune catfish in the same tank after exposure to 15,000 theronts/fish. Ich infection level was assessed by scoring 0, <50, 50-100 and >100 Ich/fish at 5 days post-infection. The antibody against Ich was determined by the enzyme-linked immunosorbent assay (ELISA) for water samples collected from tanks containing Ich immune fish. The study results showed that fish cohabited with immune fish had none or less Ich infection per fish than those cohabited with non-immune fish. Anti-Ich antibody was detected in water samples taken from tanks containing immune fish. The study results showed that immune fish partially protected the cohabited non-immune fish against Ich infection.

Technical Abstract: Fish recovered from sublethal ichthyophthiriasis acquire protective immunity against Ichthyophthirius (Ich). This study evaluated the protective effect of cutaneous antibody excreted by channel catfish immune to Ich on cohabited non-immune catfish. Non-immune and immune fish controls were separately maintained and infected with theronts. Ich infection was assessed by scoring 0, <50, 50-100, and >100 trophonts/fish at 5 days post-infection. The results of infection showed that cohabited fish at the ratio of 15 non-immune to 2 immune fish had <50 trophonts/fish. Eighty percent of the cohabited fish at the ratio of 10 non-immune to 2 immune fish showed 0 or <50 trophonts/fish. The 76% of control non-immune fish had more than 100 trophonts per fish. The infection score of the control immune fish was 0 trophonts/fish. Anti-Ich antibody was detected in water samples taken from tanks containing immune fish by ELISA after the water samples were concentrated 40x. Immunoadsorption of these water samples with theronts reduced the level of anti-Ich antibody. The results of the study showed that immune fish cohabited with non-immune fish partially protected non-immune fish against Ich infection.