Friday, August 27, 2010

How to reduce viral disease in shrimp culture?


Viral diseases have emerged a serious economic problem for shrimp farming in many country of the world. Many viruses were found negative effect on aquaculture shrimps, but have no effect in natural condition. In Indonesia and Asia in general IHHNV, TSV, and MNV have had a significant negative impact on aquaculture industries.
Even at the beginning of 2008 in Indonesia, MNV has invaded almost all the commercial farms. The attack causes the shrimp farming industry in Lampung, Indonesia almost collapse. In Asia the viral agent of WSSV and YHV have caused pandemics with catastrophic losses in culture shrimp. These problems have lead various countries in the world to close their borders or make stricter requirements for importing shrimp broadstock. Viruses are detected with deferent diagnostic techniques, such as bioassay, histology, electron microscopy, DNA probes, and immunology.

For viral diseases there are no known treatment or vaccine available. Numerous strategies have been used to try to control virus trough preventive measurement. Those measurement implemented in hatcheries for early detection of virus followed by emergency harvest and sterilization of infected area. The water treatment system, ultraviolet light, and high tank management are suggested as important elements for decreasing and controlling viral growth. Numerous virus forms have been reported as pathogenic agents when shrimp in under stress, high shrimp culture density, and inefficient shrimp larvae management.

The transmission of exotic pathogens can occur through different sources, including human migration, seabirds or other animal, and infected frozen food products. Practice that helps to decrease viral grow is removal of accumulated sediments and organic material after the shrimp harvest, followed by careful pond preparation. Closed culture system with non recirculates is another way to reduce entry of diseases into the pond.  Quarantine ponds must be treated before release in to the culture pond. Chlorine 20-30 ppm recommended for the treatment of pond water in pond preparation.

The following recommendations have been proposed to prevent the occurrence of virus diseases in pond shrimp culture in case full HDPE pond: (1) Pond preparation and water preparation: with include disinfection pond bottom prior to drying and disinfection of pond water when first filled ponds. (2) Fries Stoking: with include microscopic examination of the quality of shrimp fry, stress test, and direct observation of fries. (3) Water quality management, with include: measurement of water quality parameter on a regular basis. Control of water quality conducted to prevent the shrimp stress due to decreased water quality. (4) Feeding management, Feeding management is applied to prevent overfeeding that can cause water quality degradation.


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