ARS | Publication request: Effectiveness of early intervention with florfenicol on a Streptococcus iniae infection in blue tilapia

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 27, 2010
Publication Date: May 9, 2010
Citation: Darwish, A.M. 2010. Effectiveness of early intervention with florfenicol on a Streptococcus iniae infection in blue tilapia. North American Journal of Aquaculture. 72(4):354-360.

Interpretive Summary: Streptococcosis infection is a serious threat to the aquaculture industry. Estimated annual losses due to the infection totaled $ 10 million in the United States aquaculture alone and $100 million globally. The disease represents a real threat to intensively cultured tilapia. The current study investigated the effectiveness of florfenicol to control the mortalities caused by the disease. The results demonstrated significant mortality reduction of infected fish treated with florfenicol compared to non-treated fish. Florfenicol will provide the U.S. aquaculture industry with effective tool to curb the costly mortalities of streptococcosis.

Technical Abstract: An experimental feeding trial was performed to assess the efficacy of florfenicol (FFC) in controlling Streptococcus iniae infection in blue tilapia, Oreochromis aureus. Doses of FFC tested were 0, 5, 10, 15 and 30 mg active ingredient per kilogram of fish body weight (BW) per day. Administration of medicated feed started 6 h post challenge, by waterborne exposure to S. iniae after skin scraping, and continued for 10 consecutive days followed by a 12 d post treatment observation. Administration of FFC medicated feed for 10 d significantly increased (P<0.05) the survival of S. iniae infected tilapia from 19% in the challenged non-medicated positive control to 94, 96, 99 and 98% in the 5, 10, 15 and 30 mg FFC medicated treatments, respectively. The survival rates of the different FFC medicated treatments were not significantly different. At the conclusion of the experiment no carriers were detected in any challenged group receiving FFC medicated diet while the bacterium was recovered from the non-medicated challenged survivors of the infection. The study suggests using 10 mg/kg BW/d for 10 d is an effective treatment against S. iniae infection in blue tilapia.