Abstract:

Global production of shrimp is falling down, due to potential economic losses from disease outbreaks and is going to affect the survival of industry. This article is written in reference to avoid the fall of shrimp industry by implementing biosecurity measures in shrimp farming by two-pronged approach: excluding pathogens and elimating pathogens.

Background:

            Biosecurity, or "hazard reduction through environmental manipulation" (Plumb, 1992), is often defined as practices that reduce the number of pathogens that enter a facility. Biosecurity is the concept of protecting culture animals from contamination by diseases and of preventing the spread of diseases across boundaries, has become increasingly important with the intensification of aquaculture production systems. A significant challenge to the expansion of aquaculture production is the outbreak of disease. Potential economic losses from disease outbreaks are significant, and can affect the survival of the industry. The occurrence of disease is a combination of the health of the animal, the condition of the environment, and the presence of a pathogen. The shrimp industry has to implement a biosecure production system to prevent the spread of infectious disease among farms. By implementing biosecurity, the risk of pathological events will be reduced.

Biosecurity in shrimp farming

            In general, biosecurity is more easily implemented in small, intensive, and controlled farming systems than in outdoor and large-scale operations. Biosecurity measures in the shrimp industry can be seen as a two-pronged approach: excluding pathogens and eliminating pathogens when they are present. Lightner (2003) discussed ways of excluding pathogens from stock (i.e., post larvae and broodstock), especially through the use of quarantine and specific pathogen-free (SPF) certified stocks, and restricting imports of live and frozen shrimp. Excluding vectors and external sources of contamination and preventing internal cross contamination were suggested methods for excluding pathogens from hatcheries and farms.

            Horowitz and Horowitz (2003) described physical, chemical, and biological precautionary measures to be taken as well as a second line of defense against potential disease outbreaks. Physical measures are those that aim at preventing the intrusion of disease-carrying vectors to the farm site, and include physical barriers, water treatment, and quarantine. Chemical measures are those used to treat materials before they enter the facility. Chlorination and ozonisation are often used to treat incoming water, and iodine and chlorine are used to treat other potential vectors such as tools, footwear, and clothing. Biological measures include the use of SPF shrimp, which are readily available commercially. A second line of defense for the shrimp industry is to use specific pathogen-resistant shrimp, which, in addition to being disease-free, are resistant to specific diseases. Since shrimp do not develop a specific immune response, common immunostimulants, such as β-1-3 glucan, lipopolysaccharides, and peptidoglycans are used to improve the ability of the shrimp to prevent infection.

Horowitz and Horowitz (2003) suggested that providing better environmental and biological conditions to the infected population will increase its ability to resist diseases. They discussed the following steps: a) effect of physical measures (increase aeration, control temperature, improve the feeding regime, remove sludge and organic matter, and treat wastewater) to improve the environmental conditions, b) effect of chemical measures, including control of pH and salinity, reduction of ammonia and nitrite, and application of antibiotics, and c) to use effective biological measures, containing a mix of bacterial species to establish beneficial microbial communities under culture conditions.

Specific pathogen-free (SPF) shrimp

            In the 1990s shrimp farms around the world experienced severe economic losses due to low yields and high mortalities. The problems cut across national boundaries, species, culture system and environmental conditions. The principal disease vector appeared to be the diseased or disease carrying shrimp seed, both wild and hatchery-reared. However, the export market get great set back due to severe crop loss. The point had been made that bringing diseased or disease carrying shrimp onto farms was an invitation to disaster.

            Wyban (1993), differentiated between high-health and SPF broodstock and seed, commonly used terms that are poorly understood and often misused. It was explained that reference to high-health stock, rather than SPF, reflects a loss of control over the health status of the stock. Once stocks leave the breeding center, they are considered high-health, which means they are free from certain pathogens to the best of our ability and understanding. The process of establishing SPF stocks is shown in Fig. 1.

Fig. 1. Development of SPF shrimp.

(By Pruder, 2004)

Water exchange

            Using of raw or untreated make up water is responsible for continued disease problems when ponds are stocked with high-health shrimp seed. Fill and exchange water needs to be disinfected. Biosecure shrimp production systems stocked with high-health seed represent an emerging technology with an environmentally sustainable and economically viable alternative to conventional shrimp culture.

Fig. 2. Growout and system management.

(By Pruder, 2004)

Feed, Nutrition and Probiotics

            The restricted use of water exchange rippled through shrimp growout technologies causing major changes in feeds and feeding and the maintenance of mixed microbial populations. These matters are complex and cannot be adequately covered in this manuscript. There are unresolved challenges in designing and operating an economical biosecure shrimp production system Fig. 2. More clearly stated, biosecurity protocols is having an indirect but substantial impact on traits selected for genetic selection as well as feeds and feeding and water quality.

Management practices:

            Management practices that may be implemented to reduce the risk of introduction of pathogens include:

- Wash hands with anti-bacterial soap upon entering the facility or keep hand dip at the entrance of each and every section, so it will help us to reduce the pathogenic load to transfer it from one section to another.

- Disinfect footwear before entering the facility otherwise foot dips should be prefer mixed with bleaching powder/chlorine with appropriate level to avoid the contamination

- Access to culture area and reservoir pond should be restricted to a minimum number of well trained individuals.

- Reduce the number of visitors to a minimum and/or only people working on the farm should be allowed into the facility

- Check tray should be cleaned on after use.

- Disinfect wheels of delivery vehicles when they come onto the facility and when they leave. Establish a visitor parking area on the periphery of the facility grounds.

- Culling dead and weak shrimp is a very important strategy that can reduce the spread of pathogens from shrimp to shrimp.

- The feeding schedule should be such that the shrimp receive the best nutrition possible.

- Bird fencing and crab fencing should be checked daily, if any errors that should be corrected in time to protect the crop. Bird fencing is necessary, because birds negatively affect shrimp production by transmitting or transporting diseases, weed seeds, and parasites from pond to pond or from one facility to another. Crab fencing is also necessary, because as we know they are voracious feeder once they enter into pond they will voraciously feed on the PL or the shrimps present in pond and it consequences will be low-yield, low survival and heavy economic loss.

Conclusion

Biosecurity can be applied to shrimp aquaculture production systems through a variety of management strategies. In addition, there are a variety of risk assessments that can be used in shrimp farming. The key elements of biosecurity can be summarized as reliable sources of stock, adequate diagnostic and detection methods for excludable diseases, disinfection and pathogen eradication methods, best management practices, and practical and acceptable legislation. Nevertheless, it is almost impossible to determine the economic benefits of a biosecurity program if there is no disease outbreak, and aquaculture producers may be reluctant to adopt biosecurity measures that appear to be an additional cost. A disease outbreak in one area, however, in addition to its economic consequences in that area, may cause unintended consequences in other parts of the world.

References:

Horowitz, A. and Horowitz, S. 2003. Alleviation and prevention of disease in shrimp farms in Central and South America: A microbiological approach. Pages 117-138 in C.-S. Lee & J. O'Bryen, editors. Biosecurity in Aquaculture Production Systems: Exclusion of Pathogens and Other Undesirables. The World Aquaculture Society, Baton Rouge, Louisiana, USA.

Plumb, J. A. (1992). Disease control in aquaculture. In Diseases in Asian Aquaculture I, M.Shariff, R. P. Subasinghe and J. R. Arthur, eds. (Manila, Philippines: Fish Health Section, Asian Fisheries Society), pp. 3-17.

Pruder.G.B, 2004. Biosecurity: application in aquaculture, Aquacultural Engineering 32 (2004) 3-10.

Lightner, D.V. 2003. Exclusion of specific pathogens fro disease prevention in a penaeid shrimp biosecurity program 1-116 in C.-S. Lee and P.J. O'Bryen, editors. Biosecurity in Aquaculture Production Systems: Exclusion of Pathogens and Other Undesirables. The World Aquaculture Society, Baton Rouge, Louisiana, USA, 1-116.

Wyban, J.A., Swingle, J.S., Sweeney, J.N., Pruder, D.G., 1993. Specific pathogen free Penaeus vannamei. J.World Aquacult. Soc 24 (1) 39-45.