Dr. Celia R. Lavilla-Pitogo

Transcription

1 Current situation of emerging shrimp diseases in Asia and some recommendations to prevent their arrival and spread Hilton Hotel, Guayaquil, Ecuador September 25-28, 2017 Dr. Celia R. Lavilla-Pitogo

2 Penaeus vannamei is native to the Western Pacific coast of Latin America from Peru in the south to Mexico in the north s It s a vannamei world! s

3 Dangerous exchanges P. monodon YHV WSSV P. vannamei IHHNV MOV? LOVV? TSV BP? Reo? Slide from Dr Tim Flegel

4 Lessons from the hypothetical exotic shrimp transfer network Rapid and widespread distribution of shrimps and their hitch-hikers! Can we stop it? When?

5 It s a risky and fast-changing world! Our shrimp world is full of acronyms! It was EMS before it became AHPNS, then AHPND.

6 The Many Faces and Phases of Biosecurity Has this been effective? Requirements for successful implementation: knowledge of the enemy where and how to find it

7 The Many Faces and Phases of Biosecurity

8 Does this help?

9 What are the shrimp s enemies? 1. Acute hepatopancreatic necrosis disease (AHPND) 2. Hepatopancreatic microsporidiosis (HPM) due to EHP 1. Hepatopancreatic haplosporidiosis (HPH) 2. Aggregated transformed microvilli (ATM) 1. Covert mortality disease (CMD) 2. White spot disease (WSD) 3. Yellow head disease (YHD) 4. Infectious myonecrosis (IMN) 5. Taura syndrome virus (TSV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV) have become innocuous due to the widespread use of highly tolerant specific pathogen free (SPF) stocks of Penaeus vannamei that dominate production. We can only detect what we know.

10 Symposium on Diseases in Asian Aquaculture August 28 - September 1, 2017 in Bali, Indonesia WSSV = 7 oral presentations APHND = 7 oral presentations EHP = 4 oral presentations

11 Biosecurity Levels: National What to keep out? 1. IMNV? 2. EMS/ AHPND? 3. EHP? Be aware of what is already at home. Agreement on disease list is important.

12 Biosecurity Levels: Regional or Ecological

13 Biosecurity Level: Farms Which diseases are potential hazards? Identify and prioritize How much risk it is to the farm? Evaluate disease impact How and where can disease enter? Identify control points

14 Biosecurity Level: Farms How much will exclusion cost? Know the economic impact of disease occurrence, diagnosis and prevention Is it practical? Evaluate farm location vis-à-vis planned actions

15 Pathogen Jumps : IMNV IMNV in Indonesia (2006) IMNV in Brazil (2004) How did IMNV travel from Brazil to Indonesia?

16 Pathogen Jumps : EHP EHP in Asia (2014) EHP in South America (2017) How did EHP travel from Asia to Latin America?

17 Pathogen Jumps or pathogens in flight? Givens: 1. A virus like IMNV is an obligate pathogen and ALWAYS travels WITH SHRIMP or other hosts 2. An obligate parasite like EHP ALWAYS travels WITH SHRIMP or other hosts

18 Traditional BIOSECURITY in Shrimp Focused on viruses Systems were not prepared for bacteria or parasites AHPND is not a case of simple vibriosis, but some traditional control measures could work

19 Biosecurity for vibrios Unheard of before the advent of AHPND because vibrios are ubiquitous in the environment Difficult because vibrios: form biofilms and adhere to particles have positive affinity to chitin, an abundant material ON and IN shrimps grow on organic material, including feeds exchange genetic material with other vibrios or bacteria Microbial ecological management is key to control of vibriosis

20 Sources of Vibrio harveyi in Penaeus monodon hatcheries: Spawners release fecal material in spawning water; adherence resulted to biofilm formation on egg surface Penaeus monodon egg with bacterial plaques on the surface The bacterial plaques are composed of actively dividing cells similar to Vibrio harveyi This proves that eggs are colonized by V. harveyi before hatching and this pathogen route can be disrupted by spawner removal and egg rinsing.

21 Vibriosis in shrimp grow-out culture The shrimp pond is like a bank! A lot is deposited; very little is withdrawn. Thousands of postlarvae with + vibrios associated bacteria S h r i m p Feces, metabolites, old exoskeleton, mortalities + vibrios Feeds Rearing pond Fertilizers Vitamins, additives, binders, uneaten pellets + vibrios Algae and zooplankton grow and die Organic matter builds-up Water quality changes Microorganisms grow Biofilms form Probiotics, lime and other chemicals + vibrios + vibrios? Fertilizers

22 Avoiding too much deposits in the shrimp farm bank through Best Management Practices Reference: INFOTIP by ASEAN-SEAFDEC Shrimp toilet!!!

23 Then came EHP! EHP Disease Card: - a 5-page document that can be downloaded from the NACA website at

24 EHP Advisory from Thailand We have data indicating that most SPF stocks of P. vannamei imported to Thailand are negative for EHP, but they often become contaminated in recipient maturation facilities and hatcheries because of poor biosecurity.

25 What kind of biosecurity works for a pathogen than came in unnoticed? Although EHP does not appear to cause mortality, it is associated with severe growth retardation in P. vannamei. Management options are available. Diagnostic Methods: PCR = limited information! Wet mount of fresh samples Histopathology

26 Let s befriend that microscope once again.

27 EHP spores form clusters in the cytoplasm of infected cells (arrows)

28 Smear of shrimp hepatopancreas heavily-infected with EHP; spores form clusters in the cytoplasm (arrows)

29 EHP spores in histo slides (arrows)

30 SEVERITY GRADE TABLE FOR VARIOUS CLINICAL FINDINGS IN SHRIMP TISSUES from Dr. Lightner

31 Pcs Effect of EHP: Wide size variation during harvest Size distribution during harvest grams Size distribution of shrimps during harvest can be a reflection of the effect of high Coefficient of Variation in postlarvae during stocking

32 Uniform size of postlarvae is important Size distribution during harvest

33 EHP and biosecurity Reduction of infectious spores in the environment Very challenging because spores are RESISTANT to routine chlorine levels used by the farm Spores are not deactivated by drying Billions of spores may have been released in the environment through hundreds of pond growout activities with EHP-infected shrimp PL selection Use PCR Where EHP is present, compare production and profit data of EHP-negative and positive PLs during stocking What management strategies will improve it?

34 Prevention of EHP in Hatcheries Nauplii mouths are closed; transfer to tanks with minimum water from spawning tank Zoeae produce large amount of feces; hygiene, feeding strategy and stocking density should be reviewed Use spawning tanks; avoid straight hatchery runs

35 Prevention of EHP in growout ponds

36 Why should we use extremely high or low ph for clean up?

37 Microsporidian Spore Structure The polar tube acts like a harpoon or missile that perforates host cells. Chitin surrounding the spore wall makes it resistant to harsh environments.

38 What will make the spore eject its polar tubule, a single-use ammunition?

39 There is more to slow growth than EHP Strangulated HP tubules Granulomas in HP tubules

40 What are meaningful strategies for biosecurity? WSSV Carrier-eradication through filtration, application of crustacicide, disinfection of water, bird-nets, control of staff and equipment movement, etc. Stock SPF/SPR PL selection EMS/AHPND Disinfection of water by chlorination, microbially-mature water via ageing or application of probiotics, control of feeding and prevention of sludge accumulation, etc. Stock SPF PL selection EHP Disinfection of pond bottom by use of lime or acid; prevention of sludge accumulation, etc. Stock SPF PL selection Biosecurity strategies should match pathogen biology. How about unknown pathogens?

41 We can only detect what we know. Let s take care of shrimps we have. Thank you for your attention!