Trichinellosis in Wild and Domestic Pigs and Public Health; a Serbian Perspective

Transcription

1 Trichinellosis in Wild and Domestic Pigs and Public Health; a Serbian Perspective Sava Buncic Professor in Meat Hygiene and Safety; Dipl. ECVPH University of Novi Sad (Serbia) Milorad Mirilovic Assistant in Veterinary Economics and Statistics University of Belgrade (Serbia)

2 Summary Trichinella background EU perspective Wildlife cases Domestic pigs cases Human cases Serbian perspective Wildlife cases Domestic pigs cases Human cases Source attribution common scenarios General control strategies

3 Trichinella background

4 Trichinellosis Foodborne parasitic zoonotic (nematode worms) All Trichinella species infect mammals: mostly carnivores; rodents; omnivores including pigs; occasionally herbivores (e.g. horses) humans T. pseudospiralis also can infect birds; T. papuae and T. zimbabwensis also can infect reptiles

5 Taxonomy of the Trichinella genus (EFSA, 2004) Trichinella species or genotypes T. spiralis T1 Main natural hosts pigs, carnivores, rats Distribution areas Temperate zone, world wide T. nativa T2 (including its genotype Trichinella T6) T. britovi T3 (including its genotypes Trichinella T8, T9) T. pseudospiralis T4 T. murrelli T5 T. nelsoni T7 T. papuae T10 carnivores carnivores, occasionally pigs and wild boars carnivores and omnivores, rats, marsupials, wild birds carnivores carnivores pigs and wild boars, reptiles Arctic and subarctic zones of the Holarctic region, Stn. Canada, Ntn. USA Temperate zone of the Palaearctic region, South Africa, Namibia, Japan World wide Temperate zone of the Nearctic region Subsaharan Africa Papua New Guinea T. zimbabwensis T11 reptiles, mammals (only as experimental infection) Zimbabwe

6 Life cycle of Trichinella

7 Infectivity variations in animals Trichinella species Domestic pigs Wild boars Rats Foxes Horses Birds T. spiralis T. nativa ? - T. britovi T. pseudospir alis Infectivity: +++ highest; + lowest; - negligible (Kapel & Gamble, 2000; Trichiporse, 2005) In pigs in Europe: T. spiralis highest concern; followed by T. britovi and T. pseudospiralis.

8 Trichinellosis larvae distribution Host species Infective dose Lower infected muscle Highest infected muscle Average burden per host Pig* 50, , Fox** * Olsen et al., 1964; ** Kapel et al., 1995

9 Trichinellosis the infection Infection source-route: ingestion of the muscle tissue containing the infective larvae Clinical signs: animals: usually none humans: serious disease (life-threatening) sporadic cases: may pass unnoticed (so undiagnosed) when low level exposure to Trichinella outbreaks: more likely to be detected, so reported

10 Human infection* Etiological agent Number larvae per g meat Number larvae ingested per patient (estimate) Incubation; days (from ingestion to first symptoms) T. spiralis 46 5,000-18, ** T. britovi , * Data from outbreaks (Pozio et al., 1993; Gari-Toussaint et al, 2004) ** Incubation shorter & symptoms more intense

11 Human infection Not all larvae in ingested meat are infective The larvae infectivity, so human dose-response, are affected by: duration and temperature of meat storage before consumption: chilled storage frozen storage salt concentration i.e. water activity (a w ) of meat/product cooking regime of meat/product temperature of cooking These factors are highly variable and inter-related; so are difficult to evaluate and/or quantify

12 The EU perspective

13 Trichinella in wildlife in EU in 2007 (EFSA, 2009)

14 Trichinella in wildlife in the EU in 2007 (EFSA, 2009) Wildlife species Wild boars (non-farmed) Foxes Bears Racoon dogs Lynxes Wolves Examined 443,890 6, Positive 0.1% 2.6% 4.5% 19.4% 19.6% 21.8%

15 Trichinella in pigs in the EU in 2007 (EFSA, 2009) Domestic pigs: <0.1% of 220,680,358 examined Farmed wild boar: 0.4% of 6,615 examined The highest number of Trichinella-positive slaughter pigs reported by Poland, Romania and Spain Denmark was assigned the status of negligible risk of Trichinella in domestic pigs (Regulation (EC) No 2075/2005)

16 Trichinella in humans in the EU in 2007 (EFSA, 2009) In total: 867 reported, of which 779 confirmed, cases of human trichinellosis 0.2 per 100,000 population approx % The highest number of human cases reported in Bulgaria, Poland and Romania Trichinella species not reported in 69.1% of confirmed human cases Where reported: Trichinella spiralis in 28.2% of all cases

17 The Serbian perspective

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19 Geographic distribution of Trichinella in wild boars in Serbia

20 Trichinella in wildlife in Serbia Year (number of hunted/total number of boars) 2005 (2,631/10,781) 2006 (2,638/10,647) 2007 (2,531/10,583) 2008 (2,749/10,839) Number of positive wild boars (% of hunted) 14 (0.53%) 12 (0.45%) 32 (1.26%) 27 (0.98%) Positive other wildlife????

21 Geographic distribution of Trichinella positive pigs in Serbia

22 Geographic distribution of Trichinella negative pigs in Serbia

23 Trichinella in domestic pigs in Serbia Year Positive pigs Positive pigs (%) Positive pigs per 100,000 pig pop , , , , ,

24 Factors contributing to Trichinella in domestic pigs in Serbia Industrial pig farms with good-controlled farming practices extremely rarely involved in trichinellosis A number of extensive farms exist ( backyard ; often with access to outdoor) In 2004, the mean number of pigs on Trichinella-positive farms was 13.2, with 40.4% of the positive farms having only 1-7 pigs Slaughtering of pigs on-farm and for own consumption Such meat often not post-mortem inspected, and used for home-preparation of meat products The pig farm-level epidemiological situation could be more relevant for the Trichinella prevalence than the geographically defined region itself

25 General trend of Trichinella in pigs in Serbia: the effects of socio-economic factors? Broj svinja Y = 639, ,79x rxy = 0,20 Y = - 603, ,58x - 56,53x 2 rxy = 0, G o d i n e

26 Trichinella in humans in Serbia Year Human cases (total) Human cases per 100,000 population

27 Age and gender of human cases Age (years) >60 Total Males Fema les Total % ,00

28 Source attribution for the human Trichinellosis cases in Serbia? The published data is limited/incomplete - does not allow detailed source analysis No confirmed human cases linked to meat/pork from industrial slaughterhouses Anecdotal evidence points to home-made traditional raw meat products (fermented sausages and/or cured-anddried meat products) as important infection source Common scenario: the incriminated meat typically: From domestic pigs slaughtered under home-made arrangements Not subjected to post-mortem veterinary inspection To such meat, also meat from hunted wild boar is added where available

29 Raw, dry country ham With home-making, the production parameters vary and are largely unknown, but in industrially produced dry hams they are: Rapid-chilled pork (0 o C after 24 h; ph 5.8) Salting at 5 o C (until a w 0.96 i.e. salt in meat 4.5%) Cold smoking ( 22 o C) Drying ( 15 o C) Maturation (12-18 o C) Relative air humidity (70-78%) Final product stable at room temperature, if a w 0.90 i.e. salt in meat >4.5%, otherwise to be chill-stored In some home-made hams - viable larvae found

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31 Raw, fermented sausages (salami) With home-making, the production parameters vary and are largely unknown, but with industrially produced fermented sausages they are: Ingredients 55-70% lean pork 25-40% fatty tissue 3% curing salts (NaCl, nitrate and nitrite) 0.5% spices and flavouring Chopping and stuffing into casings Fermentation (15-40 o C; 2-5 days) and smoking Drying (semidry sausages 1-4 weeks; dry sausages12-14 weeks) In some home-made sausages - viable larvae found

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35 Principles of Trichinella controls

36 Global preventative strategies Controlling and monitoring Trichinella in wildlife On-farm biosecurity measures to prevent: a pig eating a Trichinella-infected wildlife carcass a pig eating feed contaminated with remains of infected meat or wildlife (e.g. rodents) Post-farm measures to prevent: Trichinella-infected pigs slaughtered but not tested Non-tested meat consumption without previous freezing and/or cooking

37 Testing of animals and/or meat The ielisa method for pigs: able to detect all positive pigs irrespective of their parasite burden (Gamble, 1996) - but delay between infection and seropositivity Trichinoscopy method for meat - not recommended due to lower sensitivity The most commonly used digestion method for meat (the magnetic stirrer method) for meat: 40% sensitivity at a larval concentration of larvae/gram of meat (Forbes & Gajadhar, 1999)

38 Inactivation of Trichinella spiralis by freezing (EFSA, 2004) Freezer temperature Pork group 1 ( 15 mm thickness) Pork group 2 (15-68 mm thickness) C Days Days

39 Inactivation of Trichinella spiralis by cooking Heat treatment of meat (to core temp. o C) Conventional oven References Kotula et al., 1982 Hird & Pullen, 1979; Lötzsch & Leistner, 1979 Van Sprang, 1983 Microwave oven 77 Kotula et al., 1983

40 Conclusions

41 Very grateful to colleagues from: - EFSA s BIOHAZARD Scientific Panel - EFSA s Zoonoses Unit - Serbian Veterinary Directorate - Serbian Public Health Institute for the used information and data

42 Thank you for your attention!