RENOVATE WHITE SPOT SHRIMP POND INFECTED BY WSSV (WHITE SPOT SYNDROME VIRUS)

Viral white spot disease is one of the causes of shrimp death, with up to 90-100% mortality after only 3-10 days of infection. White spot disease has a very fast spreading speed and can spread into a large epidemic causing great losses to people as well as seriously affecting the industrial shrimp farming industry.

Therefore, it is vital to incubate pathogens on white-spot diseased shrimp ponds. Farmers need to know how to reclaim their water ponds, kill pathogens spread as well as prevent pathogens from returning in the next crop.

Pathogenesis of white spot disease:

White spot disease caused by wssv virus infects many crustaceans (fresh, brackish, and saltwater) horizontally (through the aquatic environment and infected animals in ponds) and vertically (from infected adult shrimp to juvenile shrimp in hatcheries). Viruses exist in hosts, most of which are wild crustaceans, … . Therefore, the discharge of infected pond water into the natural environment not only harms the environment and neighboring ponds but also greatly affects the owner of the farming household when they take back the water carrying the disease.

Besides, the common use of tools such as fishing nets, racquets, etc., or farmers moving from one pond to another might also spread pathogens and affect the farming system. Therefore, when the appearance of ponds is contaminated with white spots caused by the WSSV virus, the treatment and improvement of the ponds should be carefully carried out to thoroughly handle the white spot pathogens that exist in the environment.

Treatment and improvement of ponds:

• When the pond shows signs of infection with white spot virus:
  • Remove the dead shrimp from the pond and destroy the dead shrimp with biocides, then collect the shrimp within 1-2 days if the shrimp reach the harvest size.
  • When the shrimp have not reached the harvest size, it is necessary to destroy the shrimp to avoid spreading into an epidemic.
• Treat dead shrimp, destroy shrimp, disinfect water, and WSSV-contaminated equipment with Chlorine 40 ppm, potassium permanganate KMnO4 10 ppm, or Formalin 70 ppm. Keep water after chlorine treatment for at least 7 days before discharging into the environment.
• Pond bottom treatment:
  • For earthen ponds (Need to pay attention to alum ponds):
    • Dry cleaning: Dredge bottom mud, plow the pond bottom, lime the pond bottom and banks, and dry the pond under the sun for 15-20 days to ensure that the bottom is dry and there is no moisture left for pathogens to hide.
    • Wet cleaning: In case it is not possible to dredge all the sludge and there are no conditions to dry the pond, it should be carried out according to the wet cleaning method. First, drain the pond as much as possible. Next, use the above-mentioned biocides with appropriate doses to treat pond sludge. (Note that during wet cleaning, do not discharge sludge into the environment, it is necessary to seal the holes and water pipes). Then proceed to use water pressure to pump the bottom of the pond and rinse it many times to clear the waste and sludge from the pond bottom. Finally, liming the pond bottom and banks, the amount of lime used for the pond depends on the pH of the pond. If conditions permit, the pond bottom should be dried for a few days and then prepared for stocking shrimp.
  • For tarpaulin pond:
    • After destroying the shrimp and disinfecting the water with bactericidal chemicals after 7 days, then drain all the water, clean it and dry it in the sun for 1-2 days. At the same time, disassemble, clean, and dry the equipment in the water such as the fan, bottom oxygen system, etc.

• After drying the pond, supply water to the pond for about 5-10 cm; use bactericidal drugs and chemicals such as potassium permanganate, Chlorine, and Formalin to soak the pond bottom and spray both banks and walkways. Treating both the bottom and the pond edge, including the way in and out of the shrimp pond, must be treated to completely eliminate white spot pathogens. Besides, repair the pond bank, cover the pond with plastic tarpaulin if possible. Build net fences and barriers to prevent crustaceans, storks, etc. from bringing disease into the pond.
• After soaking the bottom 2-3 days; drain all the water and supply water to the pond with a water level of 1m. Use Chlorine 25kg/1,000 m2 and run a fan, aerate to let Chlorine dissolve evenly and kill bacteria and pathogens that stick to the fan, aeration equipment … then drain all the water to conduct a new crop.

Preparing the water for the new crop

• Prepare water fan, install oxygen supply system, water fan suitable for pond area and shrimp stocking density.
• Pumping water into the pond through a filter bag to limit organic matter and prevent fish and other armor from being an intermediate host of white spot pathogens into the pond.
• The water is taken into the pond through the filter mesh for 2-3 days for all kinds of eggs to hatch in the pond and then proceed to kill impurities with saponin at a concentration of 15-20 ppm (15-20 g/m3 of pond water) or use other types of water. other insecticides.
• Next, disinfect the water with bactericidal chemicals such as KmnO4 10ppm, Chlorine 30ppm, and Virkon 0.6 ppm. It is recommended to use a water fan during the disinfection period.
• After disinfecting the water for 2-3 days, when checking the residual chemical content in the pond at a safe level and making sure there are no white spot pathogens, farmers can start to colorize the pond. farm and start a new crop.