Alternatives strategy to control the bacterial infection in aquaculture system
Aquaculture is the fastest growing food producing sector and also become one of the main income for millions of people around the world. A closer look at the statistics shows that the total global aquaculture production amounted to 90.4 million tonnes with an average rate of 8.6% per year and provide numerous jobs in the secondary sector (e.g. fish processing, trade and marketing) as well as in many ancillary services (FAO, 2014). However, diseases outbreak, especially caused by bacterial infection, are being increasingly reported as a significant challenge to the expansion of aquaculture production and affects the economic development of some countries. The annual economic losses associated with diseases worldwide are estimated to be in excess of US$9 billion per year and caused losses of over US$120 million in China during 1990 and 1992 (Wei 2002).
Among the bacterial pathogens, vibriosis is a well-known cause of serious problems in the aquaculture industry with a worldwide occurrence. This disease has been described as vibriosis or bacterial disease, penaeid bacterial septicemia, penaeid vibriosis, luminescent vibriosis or red leg disease (Aguirre-Guzman et al. 2004). Moreover, members of the genus Vibrio have gained attention because several species are associated with human and animal diseases and cause high losses and severe mortality of livestock in many countries, especially in shrimp aquaculture industry (Ruwandeepika 2010).
Conventional treatment of aquatic diseases caused by bacteria through the use of antibiotics are having limited value and has stimulated the emergence of bacterial resistance so that standard treatments become ineffective. Another problem created by unrestricted use of antibiotics is the presence of residual antibiotics in commercialized of aquaculture products and has led to allergy and toxicity in humans (Cabello 2006). The massive use of antibiotics for livestocks may result frequent rejections from destination exports countries due to the presence of residues from the use of prohibited antibiotics. Recently, data collected by EU, United States, Australian and Japanese authorities showed that 2,400 export consignment of Vietnamese fishery products have been rejected by Unites States authority (during 2002 – 2010), 422 shipments have been rejected by EU authorities, while Japanese and Australian authorities have refused market entry to 464 and 206 Vietnamese shipments (2003 – 2010), respectively (IDE-JETRO 2013). In view of the above circumstances, the use of antibiotics only caused severe decline in production and loses of competitiveness in export market.
Several experiments and the use of several prophylactic approach have been performed to control the bacterial diseases and have produced satisfactory results. Treatment of bacterial diseases with immunostimulant as one of the prophylactic approach have been safely used within the Aquaculture system. The word of ‘immunostimulant’ refers to any chemical compound that activates white blood cells (Leukocytes) and hence may render the animals more resistant to infection by a harmful micro-organisms in the culture environment, such as: viruses, bacteria, fungi and parasites (Raa 1996). However, there is still an urgent need for proper validation of the efficacy of immunostimulants through standardized trials to revealed the beneficial effect on the host organisms.
Parallel with the development of immunostimulants, collaborative research programs with government, researchers, and industry, are encouraged to overcome the bacterial diseases without the use of antibiotics within the aquaculture system. Based on the availability of genes information in the adaptive and innate immune system in other aquatic organisms, fish homologues can be readily identified and proper immunostimulant protocol can be developed. This mechanism is very important in order to support the sustainability of aquaculture production as the source of healthy food.
References
Aguirre-Guzmán G, Ruiz HM, Ascencio F. A review of extracellular virulence product of Vibrio species important in disease of cultivated shrimp. Aquaculture Res. 2004; 35 (1): 1395-1404
Cabello FC. Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment. Environ Microbiol. 2006; 8(7): 1137-1144
FAO. The state of world fisheries and aquaculture: opportunities and challenges. FAO Fisheries and Aquaculture Department. Food and Agriculture Organization of the United Nations. Rome. 2014
IDE-JETRO. Meeting Standards, Winning Markets: Regional Trade Standards Compliance Report East Asia 2013. e United Nations Industrial Development Organization (UNIDO); 2014 [cited 2015 July 18]. Available from http://www.unido.org/fileadmin/user_media_ upgrade/What_we_do/Topics/Quality_and_compliance/UNIDO-IDE-JETRO_Regional_ TSC_Report-East_Asia_2013_final_ebook.pdf
Raa, J. The Use of Immunostimulatory Substances in Fish and Shellfish Farming. Reviews in Fisheries Science. 1996; 4 (3): 229-288.
Ruwandeepika HAD. Expression of virulence genes of Vibrios belonging to the harveyi clade in the brine shrimp Artemia (dissertation). University of Ghent; 2010. 248 p.
Wei Q. Social and economic impacts of aquatic animal health problems in aquaculture in China. In: Arthur JR, Phillips MJ, Subasinghe RP, Reantaso MB, MacRae IH. (Eds.). Primary Aquatic Animal Health Care in Rural, Small-Scale, Aquaculture Development. FAO Fish Technical Paper No. 406. FAO. 2002.p. 55 - 61
