©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (3): 5704-5712 (2014) Outbreaks and genetic diversity of Francisella noatunensis subsp orientalis isolated from farm-raised Nile tilapia (Oreochromis niloticus) in Brazil C.A.G. Leal 1,2 , G.C. Tavares 1 and H.C.P. Figueiredo 1,2 1 AQUAVET, Laboratório de Doenças de Animais Aquáticos, Departamento de Medicina Veterinária Preventiva, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil 2 AQUACEN, Laboratório Nacional Oicial de Referência de Doenças de Animais Aquáticos, Universidade Federal de Minas Gerais, Ministério da Pesca e Aquicultura, Belo Horizonte, MG, Brasil Corresponding author: C.A.G. Leal E-mail: carlosleal@vet.ufmg.br Genet. Mol. Res. 13 (3): 5704-5712 (2014) Received May 28, 2014 Accepted June 6, 2014 Published July 25, 2014 DOI http://dx.doi.org/10.4238/2014.July.25.26 ABSTRACT. Francisella noatunensis subsp orientalis (FNO) is an emerging pathogen of warm water tilapia in a number of different countries. The disease caused by this bacterium in ish is characterized by a systemic granulomatous infection that causes high mortality rates during outbreaks. FNO has been previously described in Asia, Europe, and Central and North America. Its occurrence in South America has never been described. Since 2012, outbreaks of a granulomatous disease have been recorded in cage farms of Nile tilapia (Oreochromis niloticus L.) in Brazil. The current study aimed to identify the etiologic agent of recent francisellosis outbreaks at Brazilian tilapia farms, and to characterize the genetic diversity of the pathogen from farms with distinct geographic origins and without epidemiological connections. Bacteriological analysis