Abstract
Oreochromis niloticus (Nile tilapia) is a species having tolerance to low water quality and disease, yet in recent years its cultivation has been faced with problems related to infections with bacteria such as Aeromonas spp., Streptococcus spp., Edwardsiella spp. and Francisella spp., each characterized by mortality between 15% and 90% of aquaculture production. These economic losses are associated with poor management practices, minimal producer knowledge of disease control, and the maintenance of overly high densities; which they are directly related to electricity consumption, land use and water management, inputs of raw materials, and manpower for operating links in the value-chain. Mortalities are measured according to the degree of pathogenicity, which depends on the alteration and progression of physiological conditions of the host under the influence of environmental factors, health status and pathogen virulence. There is currently a need to confront and diminish the degree of pathogenicity, and researchers are seeking alternatives that allow the use and application of probiotic bacteria, plant extracts and vaccines. Here, we review the main pathogenic bacteria found in Oreochromis niloticus culture operations and options for controlling the appearance of bacterial pathogens in aquaculture production.
Highlights
Tilapia are a group of fish having economic, commercial and nutritional importance
A. hydrophila has been challenged by using immunostimulants such as glucan (1%) and Lactobacillus rhamnosus (1x1010 CFU g-1) in experimental tilapia cultures, where both treatments were shown to be capable of reducing intestinal damage by bacteria, the application of lactic acid bacteria can maintain the balance of intestinal microflora [50]
Bergey's Manual of Determinative Bacteriology is commonly used to identify bacterial colonies [58]. This manual was used by Evans et al [59], bacterial detection is currently performed with PCR (Polymerase Chain Reaction) which provides amplification of the 16SrRNA gene in S. agalactiae [11], A. hydrophila [47] and Francisella spp. [24], a gene unique to bacteria
Summary
Tilapia are a group of fish having economic, commercial and nutritional importance. Among the commercial species are O. niloticus, O. mossambicus, O. aureus, O. urolepis hornorum, Tilapia rendalli and T. zilli [1]. Among the disease organisms that cause mortality in tilapia are bacteria such as Flavobacterium columnare, 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. The genera Aeromonas, Streptococcus, Edwardsiella and Francisella are the leading causes of mortality of cultured Oreochromis spp., and their presence in freshwater and marine culture is related to the progression of the disease through environmental factors, host health and pathogen virulence.
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