Location: Warmwater Aquaculture Research UnitTitle: Efficacy of florfenicol for control of mortality with Francisella noatunensis subsp. orientalis in Nile tilapia, oreochromis niloticus (L.)) Author
Submitted to: Journal of Fish Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/29/2012
Publication Date: 11/8/2012
Citation: Soto, E., Kidd, S., Gaunt, P.S., Endris, R. 2012. Efficacy of florfenicol for control of mortality with Francisella noatunensis subsp. orientalis in Nile tilapia, oreochromis niloticus (L.). Journal of Fish Diseases. 36:411-418. Interpretive Summary: The project was to determine the dose of florfenicol fed orally for 10 days as a means to control infection caused by Francisella noatunensis subsp. orientalis. It was determined that a dose of 15-20 mg of FFC kg-1 bw per day for 10 days could reduce the mortality cause by this organism.
Technical Abstract: Francisella noatunensis subsp. orientalis (Fno) (syn. F. asiatica) is an emergent Gram-negative facultative intracellular bacterium. Although it is considered one of the most pathogenic bacteria in fish, there are no commercially available treatments of vaccines. The objective of this project was to determine the most efficacious concentration of florfenicol (FFC) [10, 15, or 20 mg FFC kg-1 body weight 9bw) per days for 10 days] administered in feed to control experimentally induced infections of Fno in Nile tilapia, Oreochromis niloticus ( L.) reared in a recirculating aquaculture system. The cumulative mortality of fish that recied 0, 10, 15 or 20 mg FFC kg-1 bw per day was 60, 37, 14 and 16%, respectively. Francisella noatunensis subsp. orientalis genome equivalents were detected in water from all challenged groups with a slight reduction in the concentration in the florfenicol-treated groups 4 days after treatment. The mean LOG of CFU Fno mg-1 spleen was 3-5 and was present in all challenged groups at necropsy 11 days after treatment (21 days after challenge). Results show that florfenicol administered at dose of 15 and 20 mg FFC kg-1 bw per day for 10 days significantly reduced mortality associated with francisellosis in Nile tilapia.