How to prevent and control viral diseases in shrimp culture

Transcription

1 How to prevent and control viral diseases in shrimp culture

2 Shrimp Farming in Thailand Farming Area: 80,000 Hectares No. of Farms: 35,000 Geographical Spreading: Eastern (20%) Southern (40%) Central (40%, Near Bangkok) # # # # # # # # # # # # # x x x x x x x x * # * *

3 1000 Metric tonne What caused this drastic drop? '00 1) White spot 2) Yellow head 3) Vibriosis 4) Poor management

4 1000 Metric tonne What contributed to the recovery? 1) SPF (PCR), healthy PL 2) Exclusion of virus carriers 3) Low salinity culture 4) Good management '00

5 Major viruses and the losses 1) White spot virus (WSV) 2) Yellow-head virus (YHV) 3) Monodon baculovirus (MBV) 4) Hepatopancreatic parvo-like virus (HPPV) ❷ > ❷ < 90% of mortality 10% of mortality

6 The most serious virus disease in shrimp culture --- White Spot Virus Disease (WSV) Different names, but same disease WSV (named by D. Lightner, USA) WSSV (Taiwanese) SEMBV (Thailand) Red body disease (Thailand)

7 White Spot White Spot Disease Symptoms: White spots or patches under carapace, Some with red discoloration, Feed intake heavily reduced, Massive mortality 3-7 days, PCR test positive. I Screen WSSV test kit

8 White Spot White Spot Disease Occurrence: PL to 40g shrimp; Extensive, semi-intensive, intensive farms; All salinity (including freshwater) farms; Sudden change of temperature, salinity (heavy rain) Low Temperature (22-28 celcius) in

9 White Spot

10 White Spot

11 White Spot WSV Normal E.M. photo

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13 The 2nd most serious virus disease in shrimp culture --- Yellow Head Virus Disease (YHV)

14 Yellow Head Yellow Head Disease Symptoms: Pale body color, yellowish gills & hepatopancreas Feed intake heavily reduced Severe mortality, up to 100% in 3-5 days

15 Yellow Head Yellow Head Disease Occurrence: From 20 days after stocking High stocking density farms Normal salinity Environmental deterioration

16 Yellow Head

17 Prevention and control of viral diseases Stock only virus free PL 1. PCR screening; 2. Formalin stress test Kill all the virus carriers.

18 Bio-security Viral disease transmission (pathways) From parents to larvae (Vertical transmission) x x x x x x x x From non-cultivated crustacean, insects, birds (Horizontal transmission) x x x x x x

19 Bio-security Who can be virus carriers? Species Carrier of WSV Carrier of YHV P. monodon P. merguieusis? P. chinensis? P. indicus? P. japonicus? P. styliferus? Acetes sp Metapeneus ensis Swimming crab (Portunus pelagicus) - Mud crab Small crab

20 Bio-security Who can be virus carriers? Species Carrier of WSV Carrier of YHV P. monodon P. merguieusis? P. chinensis? P. indicus? P. japonicus? P. styliferus? Acetes sp Metapeneus ensis Swimming crab (Portunus pelagicus) - Mud crab Small crab

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25 How to kill these Virus Carriers?

26 Several methods Calcium hypochlorite Formalin KMnO4 Bayer recommends

27 Dipterex95SP

28 Bio-security Which one is better? Dipterex Calcium hypochlorite Dosage 0.65ppm 20-30ppm Efficacy Kill only crustacean (virus carriers, no effect on plankton) Almost everything (plankton, beneficial bacteria) Cost 1.7 million Dong/Ht 4-6 million Dong/Ht Quantity 6.5 kg/ht 200kg-300kg/Ht

29 Bio-security Which one is better? Dipterex Formalin Dosage 0.65ppm 50ppm Efficacy Kill only crustacean (virus carriers, no effect on plankton) Almost everything (plankton, bacteria, but can't kill shrimp/crabs) Cost 1.7 million Dong/Ht 3 million Dong/Ht Quantity 6.5 kg/ht 500L/Ht Toxicity Not harmful Carcinogen

30 Bio-security Which one is better? Dosage Efficacy Cost Quantity Toxicity Dipterex 0.65ppm Kill only crustacean (virus carriers, no effect on plankton) 1.7 million/ht 6.5 kg/ht Not harmful KMnO4 Difficult to re-boom plankton and build good water color

31 Bio-security Dipterex is the product of choice for total exclusion of virus carriers x x x

32 Bio-security Dipterex Product information A.I.: trichlorfon 95% Supplied by Bayer AG ISO 9002 certified

33 Bio-security Dipterex Effectiveness Achieve high killing effect to all stages of shrimp LC50 of Acetes sp. 24hr: 0.08ppm (ph8.0, lab test) Reach total eradication of wild shrimp within 4 days at 0.65ppm.

34 Bio-security Dipterex Usage in preventing White Spot disease Fill pond with filtered water, apply Bayer Dipterex after 2 days; Dosage: 6.5 kg/ht (water depth 1.0m) 10 kg/ht (water depth 1.5m) Full aeration for 3-7 days; Introduce micro-organisms at day 4; At days, stock shrimp PL; No water exchange for the first 2 months, or reservoir water needs to be treated with Dipterex.

35 Pond Preparation schedule Day 0: Fill pond with water Day 2: Apply Dipterex, aeration Day 4: Introduce good micro-organisms, lime, fertilizer Day 10-12: Stock PL

36 How to use Dipterex in semi-intensive farms when there are no aerators/paddlewheels Add Dipterex at the water gate when water is pumped in, let the natural water current carry Dipterex all over pond; Increase dosage by 30%, at 10 kg/ht (pond depth 1.0m); When ph >8.0, wait for 8-10 days before stocking, When ph <7.5, wait for days.

37 How to kill crabs with Dipterex? Unlike shrimp, crabs can walk away when Dipterex is applied. Method: Prepare bait contains Dipterex as follows: Mix Dipterex with minced trash fish, at g/kg, Place the bait at different sites along the pond bank Collect dead crabs the next day. Apply the bait at the same time when Dipterex is used in water.

38 How to kill crabs with Dipterex? Method: Use netting (30-50cm high) around pond bank With plastic linings

39 Why Bayer Dipterex? A.I. not less than 95% ISO 9002 Cost effective No caking Registered to use in aquaculture No strange odor Guarantee! full eradication of virus carriers