Edwardsiella tarda, Aeromonas spp., Vibrio spp., Francisella spp., Streptococcus agalactiae and S. iniae. Some of these pathogens are distributed throughout tropical and temperate regions where warmwater species, such as Nile tilapia, are commonly cultured. Merck Sharp and Dohme Corp. (MSD Animal Health) [2] mentions that mortalities increase with density (number of fish m-3) [3], and James et al. [4] and Bondad-Reantaso et al. [5] indicate that aquacultural health problems and the introduction of species promote the emergence of diseases. According to Snieszko [6], disease is related to the interaction between fish, pathogens and their waterways. When an organism is exposed to a bacterial pathogen in an unfavorable environment (e.g. poor water quality or excess of organic matter), disease incidence is higher because the balance between the pathogen, host and aquatic environment destabilizes. However, fish contain a high bacterial diversity, which results from a symbiotic effect among bacteria and tolerance by fish that protect them when adapting to nutritional changes and assimilation of food in the digestive tract [7].