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Location: Warmwater Aquaculture Research Unit

Title: Efficacy of Florfenicol for Control of Mortality Caused by Flavobacterium columnare Infection in Channel Catfish, Ictalurus punctatus (Rafinesque)

item Gaunt, P - Mississippi State University
item Gao, D - Mississippi State University
item Sun, F - Mississippi State University
item Endris, R - Mississippi State University

Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2010
Publication Date: 6/23/2010
Publication URL:
Citation: Gaunt, P.S., Gao, D., Sun, F., Endris, R. 2010. Efficacy of Florfenicol for Control of Mortality Caused Bby Flavobacterium columnare Infection in Channel Catfish, Ictalurus punctatus (Rafinesque). Journal of Aquatic Animal Health. 22:115-122.

Interpretive Summary: Columnaris disease caused by the bacterium Flavobacterium columnare is a significant cause of mortality in catfish. This study evaluated the efficacy of florfenicol (FFC) to control mortality in catfish infected with F. columnare in aquaria. Thirty aquaria (with 20 fish/tank) were randomly assigned treatment one time a day for 10 days of either unmediated feed or feed medicated with 10 mg FFC /kg fish body weight. After the 10 day treatment period all fish were fed unmedicated feed for 14 days. Catfish treated with FFC medicated feed had significantly fewer deaths and positive cultures for F. columnare than fish treated with unmedicated feed. Lesions on dead fish were consistent with columnaris disease. There was no difference in either feed consumption or weight gain between the FFC medicated fish and the unmediated fish. Florfenicol medicated feed at a dose of 10 mg FFC/kg body weight was an efficacious control of mortality from F. columnare infection in catfish.

Technical Abstract: The efficacy of florfenicol against Flavobacterium columnare infection was studied in channel catfish (Ictalurus puntatus) fingerlings in 80L aquaria. Non-abraded fish were challenged by immersion on Day 0. Thirty 80 liter tanks were randomly assigned in equal number to two treatment groups, either treated with 0- mg florfenicol / kg body weight (unmedicated feed) or 10- mg florfenicol /kg body weight in medicated feed for ten consecutive days. Mortality was monitored during the 10-d treatment period and during a 14-d post-treatment observation period. At the end of the 14-d post-treatment observation period, all fish were euthanized, examined for gross lesions, and cultured for F. columnare. Significantly fewer (p < 0.001) florfenicol-medicated catfish (8.0%) died in comparison to unmedicated catfish (54.2%). F. columnare was cultured from 15.0% of FFC-medicated-fish compared with 68.9% of fish in the unmedicated group. The gross lesions in fish were consistent with columnaris disease and F. columnare was cultured from 99.5% of dead fish. No differences were observed in weight gain and appetence between the medicated and non-medicated groups. For the F. columnare strain used in this study, the minimal inhibitory concentration of florfenicol ranged from 0.5-1.0 mg/mL in 30 bacterial cultures obtained from infected fish, and the mean disk diffusion zone of inhibition was 40 mm. No adverse effects occurred in the florfenicol-medicated fish. Florfenicol at a dose rate of 10 mg/kg bw for 10 days was efficacious and safe for control of mortality from F. columnare infection in catfish.