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Last Update: 21 Oct 2018
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Jln. Tun Abdul Rahman Yakub, Petra Jaya, 93050 Kuching, Sarawak
Tel. No.: 082-441000   Fax No.: 082-447821
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Department of Agriculture Sarawak, 7th, 12-14, 16-17th Floor, Menara Pelita, Jln. Tun Abdul Rahman Yakub, Petra Jaya, 93050 Kuching, Sarawak

Tel. No.:  082-441000  
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White Spot Shrimp DiseaseWhite Spot Shrimp Disease
WHITE SPOT SHRIMP DISEASE

Background

The White Spot Disease of shrimps is caused by a type of virus called the "Systemic Ectodermal and Mesodermal Baculovirus (SEMBV) which was first detected in 1993 attacking white shrimps (Penaeus chinensis) in China.  The same virus infection was also detected to have infected white shrimps (Penaeus merguiensis, P Indicus) and Tiger Prawn (Penaeus monodon) in India in 1994.  Similar disease infection was reported in Taiwan, Japan, Indonesia and Thailand.

In Malaysia, the disease was detected at the end of 1995 in Kedah.  In early 1996, the disease spread to Perak, Selangor, Johore and Terengganu which had resulted in the National outbreak.  However, shrimp farmers in Sarawak and Sabah should not be complacent as they are not spared from getting the disease.  This had caused a great loss to the farmers and it is feared that his will threaten the National aquaculture development.

Mode of Infection

This is a water-borne disease spread by host found in the water or ponds, such as zooplankton, crabs and fish.  Birds can also be a carrier through its faeces.

Early Signs of Infection

  • Shrimps appear weak and not active.
  • The shrimps will appear on the water surface, swimming and gathering around the pond which makes it easy to collect or be attacked by predators.
  • Loss of appetite.
Clinical Symptoms
  • Its colour turns pale or reddish.
  • Appearance of white spots of 0.5mm - 2.0mm diameter, especially at the inner surface of the shell on its head (carapace) and at the end of the tail.  Finally, the whole body will be covered by white spots.
  • Death will occur when the whole body is infected by white spots.
  • Death will occur gradually until it reaches 100% within: 
            2-3 days as in the young shrimps/juveniles, 
            3-10 days for adult shrimps
  • Serious infection will cause the stomach to shrink and damage to the gills.


Treatment

So far there is no effective treatment for the disease.

Control of the Disease

Infected Shrimps and Their Disposal

  • Farmers arerequired to follow the advice given by relevant officers from the Department of Agriculture with regards to the movement and disposal of the infected shrimps.  The infected shrimps should never be thrown back into open waters.
     

Infected Pond

Farmers should carry out total cleaning up according to the following procedures:

  • No water must be discharged from infected pond into the open waters.
  • Apply chlorine (Calcium hypochlorite with 60% active ingredient) at the rate of 300 kg/hectare and leave at least 72 hours before the ponds are dried.
  • Dry up the ponds and leave them exposed to the sunlight for two weeks until the bottom of the pond is dried up .  The dried sediments are then collected and suitably disposed off.
  • Farmers are advised to stop production (break cycle) for at least one season if their ponds are infected by the disease to avoid further infection.  Seek advice from the Inland Fisheries Branch of the Department of Agriculture before starting a new cycle.

Good Culture Practices For Disease Prevention

  • Treat the culture water with Chlorine (Calcium hypochlorite with 60% active ingredient) at the rate of 300 kg/hectare for at least 72 hours before use.
  • Water should be changed at the rate of at least 10% per day.
  • The Secchi-disc reading must be between 30cm - 40cm.
  • Dissolved oxygen content should not be less than 4 mg/l.
  • High stocking rate will encourage disease infection.  The recommended stocking rate by the Department is NOT MORE THAN 30 pieces/m2.
  • Use quality feed and do not use old stocks and mouldy feed.  Avoid fresh food of fish meals.
  • Biosecurity (e.g. having dogs freely running around in the farm is not compatible with good management practice.)

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