Fishborne Zoonotic Parasites in South East Asian Freshwater Aquaculture: Detection and risk mitigation throughout the commercial production chain

Transcription

1 Fishborne Zoonotic Parasites in South East Asian Freshwater Aquaculture: Detection and risk mitigation throughout the commercial production chain

2 1. Asian aquaculture

3 Global aquaculture production by region = 52 million tonnes in By Quantity By Value Bostock J et al. Phil. Trans. R. Soc. B 2010;365: by The Royal Society

4 Mean freshwater aquaculture products as a function of land area (km -2 ). Red: kg Orange: kg Green: 0-50 kg

5 Major Fish Exports From Asia Catfish ( Pangasianodon hypothalmus): Tra, Sutchi, Basa Tilapia ( Orechromis niloticus, O. mossambicus) Red Tilapia

6 Value (2008) Species Tonnes 10 year increase Inrease in value Catfish 1,380, % 197 % Tilapia 2,334, % 28 % Bostock J et al. Phil. Trans. R. Soc. B 2010;365:

7 Exporters to EU Country/Spec ies Tilapia China ++ + Vietnam + ++ Thailand + + Bangladesh + + Pangasius catfish ++ Major export industry + Significant domestic industry

8 Vietnam Since 2005, the EU has imported 35-40% of all catfish from Vietnam.

9 2. Production and Processing Systems

10 Developmental stages of Tra catfish Hatchery: Fry (8-10 mm) Nursery: Juvenile Grow-Out (55-60 mm) g

11 River Cage Culture of Catfish

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13 Pond Grow-Out of Catfish

14 Feeding time.

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16 Tilapia stages Nursery: Juveniles g Grow-Out 600 g

17 Cage Grow-Out Of Tilapia

18 Pond Grow-Out of Tilapia

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20 Processing of catfish

21 Preparation of fillets Freezing for export.

22 3. Diversity, prevalence and biology of fishborne parasites (FBP) in SE Asia aquaculture

23 O. felineus O. viverrini Cl. sinensis Trematodes ( flukes ) are the important zoonotic parasites in SE Asia freshwater fish. Liver flukes ( Opisthorchiidae) Clonorchis sinensis Opisthorchis viverrini Adults from liver (7.4 x 1.5 mm) Metacercaria from fish ( mm)

24 2. Intestinal Flukes ( Heteropyhidae; Echinostomatidae) ( minute intestinal trematodes 1.5-x 0.5 mm) Most Common Asian Fishborne Zoonotic Trematodes Haplorchis taichui H. yokogawi H. pumilio Metacercaria ( mm)

25 Life Cycle Essentials?? Infect fish Vector snails E g g s CERCARIA Intestinal flukes only

26 Liver flukes Intestinal flukes

27 Greatest Risk Factor for Humans: Improperly Prepared Fish Dishes

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29 Liver flukes Disease and Public Health Impact liver and bile duct enlargement, chronic irritation, jaundice, anorexia, cholangitis, pancreatitis cholangiocarcinoma : in NE Thailand- 129/100,000 (vs 1-2/100,000 in western countries). Classified as a Group 1 Carcinogen by IARC. Intestinal flukes Villous atrophy, inflammation Malabsorption/weight loss Diarrhea, anorexia Occasionally egg induced inflammation of heart, brain and spinal cord

30 Summary of some recent prevalence surveys of cultured fish for zoonotic metacercaria in SE Asia* Country Fish species Range of prevalence Vietnam River catfish Pond catfish Tilapia Carps Number of surveys China Tilapia Thailand Carps Tilapia (pond) * Examined by pepsin digestion

31 Typical pond for household use to rear carps. Reservoir host

32 Farming practices: Small farms The VAC System: Fertilization with feces Fibozopa

33 3. Export controls for FBP: inspection and inactivation

34 List I Exporting Countries: EC Council Directive 91/493/EEC CHINA INDONESIA MALAYSIA PHILIPPINES SINGAPORE THAILAND VIET NAM The European Union (EU) delegates the control of food safety to a Competent Authority in each LIST I country, who in turn ensures that exporting farms, vessels and processors are producing safe food under a system equivalent to that in the European Union - the principle of equivalence.

35 Example: EU regulations on EXPORTS to the EU must be accompanied by certificates which confirm that the shipment complies with the conditions stipulated in the Decision ( EC ) 852/2004, Article 48 of Decision ( EC ) 882/2004 and Article 14 of Decision ( EC ) 854/2004 on the organization and regulation of inspection activities for food products of animal origin. Vietnamese Competent Authority requires Vietnam exporters to comply with these EC regulations, and requires exporters to submit samples for testing to ensure their products meet the EU and MARD regulations.

36 Primary inspection for fish: Candling

37 Distribution of zoonotic metacercariae in catfish and tilapia Fish species Section % of total MC recovered Catfish Head 8 Catfish Fins 24 catfish Muscle 68 Tilapia Head/Fins Muscle 47 53

38 Defect levels by candling examination EFSA * ( Codex Alimentarius): 2 or more metacercariae/ kg, or if parasite infection causes tissue change in 5% or more of sample by weight. US FDA: Allows up to 50 metacercariae/100 lbs of fish- if less than 20% of fish are infected.(marine whitefish) * Annex II, Chapter IX, EC Regualtion 852/2004.

39 The inactivation of parasites in fish. Freezing Cooking (70 o C for 30 min). Pasteurizing Brining or pickling (not a complete control) Physical removal at candling (not a complete control) Irradiation (0.5 kgy)- effective but not yet utilized.

40 CONTROL BY FREEZING* Metacercariae are killed by freezing and storing at: -10 o C for 10 days. -20 C or below for 3-4 days (total time) -28 o C for 28 hrs. storing at -18 C for duration of transit and distribution or by freezing at -35 C or below until solid and storing at - 35 C or below for 15 hours. * EFSA: Annex III, Section VII, Chapter III of Regulation 852/2004

41 Chilled Fillets Tilapia exports to USA in 2013 Demand for high value fresh/chilled (air-flown) tilapia fillets continued to rise despite increasing prices. During the first six months of 2013 imports of fresh/chilled tilapia fillet shot up 65%. Globefish FAO Jan 2014 Tilapia

42 Laboratory Methods Confirming fish infections with metacercariae. Compression Technique Press tissue between glass slides and examine under a microscope. Fast, economical. Exact location of infection site can be determined.

43 Metagonimus Mc. in the scale of fish Centrocestus Mc. in the viscera of fish Echinochasmus Mc. in the gill of fish Metacercariae as seen by compression of fish tissue. Sohn and Chai 2004)

44 Digestion Method - pepsin enzymatic digestion of fish flesh to liberate parasites.! "#$%&%! " # " $%&'()*'" &+ Quantiative, useful for taxonomic determination! "#$%8 % 7&082)*'" &%+=>, 5%?@; %8% A@B; (<% ' #$()* % +, -. %/%$#$()* %0%, -1%2 3%4 56%)* %78% 2 3%9 : "#; <%! "#$%=%, ) -. +) &/+-01%%& ! "#$%C% 7-" 9)*'" &+" :+ # %*)0%10) 1') %+ %

45 Zoonotic metacercariae isolated by pepsin digestion. Heterophyid Intestinal Flukes Liver Flukes Echinostome Intestinal Flukes

46 Excretory Vesicle Key characters in identification of trematode metacercariae. 1 Size and shape of cyst: Spherical or elliptical-spherical in most cases, and thickness of wall. 2 Size and placement of suckers, reproductive structures, presence of hooks and spines, etc. Hooks

47 Murrell, Chai and Sohn 2006 (unpublished).

48 Molecular methods

49 4. Prevention of infection during production of fish Most important risk factor for fish: exposure to cercariae. Fibozopa

50 Critical Control Intervention Points Fibozopa

51 Clausen et al PLoS NTD 6: e1945 Clausen, J.H. et al. (2013. Aquaculture 416.

52 BEFORE intervention AFTER intervention

53 Intensity of infection Intensity of infection ( No. Zoonotic metacerciae/fish) 14 Intervention Non-intervention Fry 3 w 6 w 9 w Fry 3 w 6 w 9 w Age of fingerlings (weeks)

54 Interesting, but I prefer mine fried.

55 Specialty products: Eels Gnathostoma spinigerum Advanced third stage larva

56 Prevalence in swamp eels in US ethnic markets ) Location Prevalence (%) New York, NY 30 Orlando, Fla 20 Atlanta, Ga 42

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60 FIBOZOPA LABORATORY MANUAL IDENTIFICATION OF ZOONOTIC METACERCARIAE FROM FISH Prepared for FIBOZOPA Project by Professor K. Darwin Murrell, WHO/FAO Collaborating Centre for Emerging Parasitic Zoonoses, Department of Veterinary Pathobiolgy, Royal Veterinary and Agricultural University,Denmark Professor Jong-Yil Chai, Department of Parasitology, Seoul National University College of Medicine, Seoul, Korea Professor Woon-Mok Sohn, Department of Parasitology, College of Medicine, Gyeonsang National University, Chinju, Korea