Toxoplasmagondiiinredmeatandmeatroducts（精编版）

1、institute of environmental science & research limitedchristchurch science centrelocation address : 27 creyke road, ilam, christchurchpostal address: p o box 29 181, christchurch, new zealandwebsite: www.esr.cri.nza crown researchinstituterisk profile:toxoplasma gondii in red meatand meat product

2、sprepared as part of a new zealand food safety authoritycontract for scientific servicesbydr rob lakedr andrew hudsonpeter cresseyaugust 2002client reportfw0138risk profile:toxoplasma gondii in red meatand meat productsprofessor ian shawfood safety programme managerdr rob lakerosemary whyteproject l

3、eaderpeer reviewerrisk profile: toxoplasma gondii in red meataugust 2002and meat productsdisclaimerthis report or document (“the report”) is given by the institute of environmental science andresearch limited (“esr ”) solely for the benefit of the new zealand food safety authority( “nzfsa ”), public

4、 health services providers and other third party beneficiaries as definedin the contract between esr and the new zealand food safety authority, and is strictlysubject to the conditions laid out in that contract.neither esr nor any of its employees makes any warranty, express or implied, or assumesan

5、y legal liability or responsibility for use of the report or its contents by any other person ororganisation.risk profile: toxoplasma gondii in red meataugust 2002and meat productsacknowledgmentsthe authors would like to thank roger poland, programme coordinator, animal healthand welfare, ministry o

6、f agriculture and forestry; peter davies, institute of veterinary,animal and biomedical sciences, massey university; and murray wilkins, agvax, forhelpful discussions.risk profile: toxoplasma gondii in red meataugust 2002and meat productscontents1introduction.12hazard identification: the organism.42

7、.1 toxoplasma gondii .42.1.1the organism.42.1.2growth and survival.42.1.3inactivation (ccps and hurdles).42.1.4sources.53hazard identification: the food.63.1 relevant characteristics of the food: red meat and meat products.63.2 the food supply in new zealand.73.2.1imported food.74hazard characterisa

8、tion: adverse health effects.94.1 symptoms .94.2 dose response.104.3 high risk groups in the new zealand population.104.3.1pregnant women.104.3.2immune compromised.105exposure assessment.125.1 the hazard in the new zealand food supply.125.1.1test methodology.125.1.2prevalence/incidence in animals in

9、 new zealand.125.2 food consumption: red meat and meat products.135.3 qualitative estimate of exposure.145.3.1number of servings and serving size.155.3.2frequency of contamination.155.3.3predicted contamination level at retail.165.3.4growth rate during storage and most likely storage time.165.3.5hea

10、t treatment.165.3.6exposure summary.165.4 overseas context.175.4.1seroprevalence in animals.175.4.2prevalence in animal tissue.186risk characterisation.196.1 adverse health effects in new zealand.196.2 adverse health effects overseas.206.2.1incidence.206.2.2contribution to outbreaks and incidents.22

11、6.3 qualitative estimate of risk.236.4 risk categorisation.246.5 summary.247risk management information.25risk profile: toxoplasma gondii in red meataugust 2002and meat products7.1 economic costs.258conclusions.278.1 description of risks to new zealand consumers.278.1.1risks associated with red meat

12、 and meat products.278.1.2risks associated with other foods.278.1.3quantitative risk assessment.278.2 commentary on risk management options.279references.29appendix 1: categories for risk profiles.33risk profile: toxoplasma gondii in red meataugust 2002and meat productslist of tablestable 1:livestoc

13、k numbers for new zealand in 2001.7table 2:new zealand domestic meat consumption per capita 1985, 1995, 1996 & 1999(kg/person/year).13table 3:international comparison of meat consumption, 1998 (kg/person/year).13table 4:mean estimates of new zealand domestic meat consumption (total populationove

14、r 15 years), 1997 and estimates of meat available for consumption, 1996(g/person/day).14table 5:reported prevalence of toxoplasma gondii antibodies in overseas animals. 17table 6:reported prevalence of toxoplasma gondii cysts in overseas animal tissue. 18table 7:reported prevalence of toxoplasma gon

15、dii antibodies in pregnant women inhamilton.19table 8:seroconversion rates for toxoplasma gondii infection.21table 9:reported prevalence of antibodies to toxoplasma gondii in various populations .21table 10:summary of information on outbreaks of infection with toxoplasma gondii . 22list of figuresfi

16、gure 1risk management framework.1risk profile: toxoplasma gondii in red meat1august 2002and meat products1introductionthe purpose of a risk profile is to provide contextual and background information relevant toa food/hazard combination so that risk managers can make decisions and, if necessary, tak

17、efurther action. the place of a risk profile in the risk management process is described in“food administration in new zealand: a risk management framework for food safety”(ministry of health/ministry of agriculture and forestry, 2000). figure 1 outlines the riskmanagement process.figure 1risk manag

18、ement frameworkfigure reproduced from “ food administration in new zealand. a risk management framework for food safety”(ministry of health/ministry of agriculture and forestry, 2000).in more detail, the four step process is:1. risk evaluation?identification of the food safety issue?establishment of

19、 a risk profile?ranking of the food safety issue for risk management?establishment of risk assessment policy?commissioning of a risk assessment?consideration of the results of risk assessmentrisk profile: toxoplasma gondii in red meat2august 2002and meat products2. risk management option assessment?

20、identification of available risk management options?selection of preferred risk management option?final risk management decision3. implementation of the risk management decision4. monitoring and review.the risk profile informs the overall process, and provides an input into ranking the foodsafety is

21、sue for risk management. risk profiles include elements of a qualitative riskassessment. however, in most cases a full exposure estimate will not be possible, due to datagaps, particularly regarding the level of hazard in individual foods. consequently the riskcharacterisation part of a risk assessm

22、ent will usually rely on surveillance data.risk profiles also provide information relevant to risk management. based on a risk profile,decisions are made regarding whether to conduct a quantitative risk assessment, or takeaction, in the form of gathering more data, or immediate risk management activ

23、ity.toxoplasma gondii was chosen as a topic for risk profiling as the significance of humaninfections in new zealand was identified as a knowledge gap in a review conducted in 1998(hasell, 1998).the sections in this risk profile are organised as much as possible as they would be for aconventional qu

24、alitative risk assessment, as defined by codex (1999).hazard identification, including:?a description of the organism?a description of the food grouphazard characterisation, including:?a description of the adverse health effects caused by the organism.?dose-response information for the organism in h

25、umans, where available.exposure assessment, including:?data on the consumption of the food group by new zealanders.?data on the occurrence of the hazard in the new zealand food supply.?qualitative estimate of exposure to the organism (if possible).?overseas data relevant to dietary exposure to the o

26、rganism.risk profile: toxoplasma gondii in red meat3august 2002and meat productsrisk characterisation:?information on the number of cases of adverse health effects resulting from exposure tothe organism with particular reference to the food (based on surveillance data)?qualitative estimate of risk,

27、including categorisation of the level of risk associated withthe organism in the food (categories are described in appendix 1).risk management information?a description of the food industry sector, and relevant food safety controls.?information about risk management options.conclusions and recommend

28、ations for further actionnote: earlier versions of this document were produced as part of a project undertaken by esrand jointly directed by the ministry of health and the ministry of agriculture and forestry.responsibilities for food safety were combined into the new zealand food safety authority(n

29、zfsa) in july 2002.the australia new zealand food authority (anzfa) became food standards australia newzealand (fsanz), also in july 2002.information and reports published by the older organisations have been referenced to thosenames.risk profile: toxoplasma gondii in red meat4august 2002and meat pr

30、oducts2hazard identification: the organismthe following information is taken from a data sheet prepared by esr under a contract forthe ministry of health in 2000-2001. the data sheet is intended for use by regional publichealth units.2.1toxoplasma gondii2.1.1the organismthis organism is an obligate

31、intracellular protozoan parasite that is able to infect warm-blooded animals and birds. the results of infection can range from being asymptomatic inhealthy adults to miscarriages with death of the foetus.the organism has a complicated life cycle with numerous stages. infected cats are the onlyspeci

32、es to shed oocysts in their faeces which subsequently sporulate in the environment.these can be ingested by humans or animals, and the sporozoites released enter the body. theinvasive tachyzoites, which are derived from the sporozoites, then invade body tissues.meat animals that have been infected e

33、ventually produce cysts (which contain large numbersof bradyzoites) in muscle tissue. if eaten by humans the digestive juices break down the cystto release the bradyzoites, which transform to tachyzoites and cause infection.note that in microbiological terms “d” refers to a 90% (or decimal or 1 log

34、cycle) reductionin the number of organisms.2.1.2growth and survivalgrowth: the organism does not grow in foods or in other environments outside of a suitablehost.survival: the resting stage, or oocysts, can survive outside of susceptible hosts.temperature: oocysts in faeces or suspended in water ret

35、ained infectivity for up to 400 daysat temperatures ranging from 4 to 37oc. sporulated oocysts are killed to some extent byfreezing at -21oc, but unsporulated oocysts are killed within 1-7 days at this temperature.water activity: sporulated oocysts are gradually inactivated by drying. encysted t. go

36、ndiimay survive for 4 days in 8% nacl.2.1.3inactivation (ccps and hurdles)temperature: cysts in pork were killed in 336 seconds at 49oc, 44 seconds at 55oc, 6seconds at 61oc. microwave heating to 65oc gave variable results for the inactivation ofcysts in mutton.d times for bradyzoites are reported t

37、o be; 53.5 minutes at 49oc, 5.8 minutes at 55oc, 3.8minutes at 61oc and 3.6 minutes at 67oc.risk profile: toxoplasma gondii in red meat5august 2002and meat productscysts present in pork and mutton are inactivated by freezing at temperatures of -9.4oc orlower.preservatives: the organism is thought to

38、 be susceptible to curing agents used in meatproducts.radiation: exposure of tachyzoites to 70 j m-2 ultraviolet light renders the organism non-infectious. a dose of 1 kgy ionising radiation would ensure that pork is free of the organism.2.1.4sourceshuman: person-to-person spread has not been descri

39、bed, but sub-clinical human infection canbe chronic and become activated if the immune system becomes weakened.animal: the significance of beef cattle in the epidemiology of toxoplasmosis is unclear andpigs are considered to be a more significant source of infection. piglets can be killed bytoxoplas

40、mosis, but older infected pigs are asymptomatic.sheep and goats can be infected by the organism, and the major clinical effect is abortion.other animals that can be infected include birds, horses, game animals (e.g. deer), mice andrats, marsupials and dogs. cats are the only animals known to shed oo

41、cysts. animals such asflies that have come into contact with infected faeces may harbour the organism.food: meat containing toxoplasma cysts may act as a source of human toxoplasmosis.infected meat and milk from cattle is not considered to be important, but undercooked pigmeat is considered to be si

42、gnificant. sheep and goat meats are also a potential source ofinfection for humans. goat milk has also been implicated as a source of disease.poultry could be a source of infection if it is insufficiently cooked.other meats that may be sources of infection include rabbit, horse, and game (e.g. deer)

43、. it hasbeen detected in one of 67 ready-to-eat cured meat samples (ham).vegetables, which may be contaminated with soil, are another potential source, particularlyfrom gardens where there may be cats. unpasteurised goat milk has been implicated in someoutbreaks (smith, 1993).environment: it is poss

44、ible that the consumption of infected water can result in infection, andoutbreaks have been attributed to this. the source of contamination is thought to be membersof the cat family. oocysts have been isolated from soils, and soils may be importantintermediates in the transmission from cats to human

45、s via buried faeces.transmission routes: potentially by contact with soil, consumption of contaminated water,contact with cat faeces, or by consumption of contaminated meats (and possibly foods thathave been in contact with contaminated soil).risk profile: toxoplasma gondii in red meat6august 2002an

46、d meat products3hazard identification: the food3.1relevant characteristics of the food: red meat and meat productsmeat containing toxoplasma cysts is regarded as the major source of infection for humantoxoplasmosis (the organism is not considered to be transmitted from person to person). asthe organ

47、ism does not grow outside a live host, the characteristics of the food group are lessrelevant in terms of contributing to risk. specific meats which have been found to containcysts include (smith, 1991):?beef and veal?small game animals (including rabbits)?fowl (chicken and pigeons)?horse meat?deer

48、and elk (wapiti) meat?mutton, lamb and goat meat?porkbeef and veal are generally considered as less likely to be contaminated; clinical disease israre in cattle and the organism is rapidly eliminated from tissues (smith, 1991). however, theorganism has been found in surveys of cattle tissue, and cro

49、ss contamination from othermeats during processing is a potential source of contamination (smith 1991; 1992).these meats all fall into the risk profile category of red meat, apart from chicken and pigeons.while raw meats have been most commonly implicated, cured meats such as ham have alsobeen shown

50、 to occasionally contain cysts (warnekulasuriya et al., 1998).although visual or serological testing can be utilised in the field or slaughterhouses to preventother parasites (taenia solium and trichinella spiralis) from entering the food supply, this isnot an option for toxoplasma gondii due to the

51、 length of time and complexity of theextraction procedures and assays (gamble, 1997). consequently control mechanisms mustfocus on destruction of cysts via cooking or other mechanisms.as indicated in section 2 above, cooking to an internal temperature of 50c or above rapidlydestroys toxoplasma cysts

52、. an investigation into alternative cooking procedures, usingmostly infected mutton as the model has been conducted (lundn and uggla, 1992). thestudy used the mouse bioassay as the end point, examining brain tissue microscopically andserum for antibodies. after freezing (-20c for 54 hours), curing w

53、ith salt and sugar, orsmoking (24 hours at less than 50c following salt injection) all samples were found to benon-infective. however, two of four samples of microwaved steak remained infectivealthough a thermometer inserted into the meat registered 65c or more. this was ascribed touneven heating of

54、 the meat in a microwave oven.another study has shown that freezing at -12c or below inactivates toxoplasma gondiitissue cysts, although cysts could survive freezing at higher temperatures for several days(kotula et al., 1991).in new zealand, meat cuts presented for retail sale (butchers, supermarke

55、ts) will not usuallyrisk profile: toxoplasma gondii in red meat7august 2002and meat productshave been frozen. however, wholesale meat used in the production of sausages, meat pies,etc. is likely to have undergone freezing at some stage (graeme keeley, technical manager,ppcs, personal communication).

56、 only a small proportion of meat for domestic consumptionwill have been frozen prior to sale (clyde daly, agresearch, personal communication). thecurrent chilling regime used for “quality mark” meat production requires a temperature of7c or less prior to shipping, with 4c achieved by retail sale.3.2

57、the food supply in new zealandthere are 17,000 commercial sheep and beef cattle farms in new zealand, most of which areowned and operated by farming families. livestock numbers for new zealand in 2001 areshown in table 1 (maf, 2001).table 1:livestock numbers for new zealand in 2001main classes of li

58、vestock (millions) in 2001total sheep43.99total beef4.98total dairy4.73total pigs0.37total deer2.66for the year ending september 2001 new zealand produced 596,300 tonnes of beef and vealmeat (1% of world production). over 80% of this production was exported, representing10% of the world trade in bee

59、f (maf, 2001).approximately 80% of new zealands sheep meat production is exported. the majority isfrozen, but chilled meat exports now represent 12% of the total. according to the 2001situation and outlook for new zealand agriculture and forestry (maf, 2001) totalproduction for the year ending septe

60、mber 2001 was approximately 440,100 tonnes of lamband 126,800 tonnes of mutton. from this production, 360,600 tonnes of lamb and 100,000tonnes of mutton were exported.new zealand venison production is expected to reach 32,000 tonnes in 2001-2002.approximately 80% of production is exported to europe.new zeal