Scientific Opinion on a Quantitative Microbiological Risk Assessment of Salmonella in slaughter and breeder pigs 1

Transcription

1 SCIENTIFIC OPINION Scientific Opinin n a Quantitative Micrbilgical Risk Assessment f Salmnella in slaughter and breeder pigs 1 ABSTRACT EFSA Panel n Bilgical Hazards (BIOHAZ) 2, 3 Eurpean Fd Safety Authrity (EFSA), Parma, Italy This Quantitative Micrbilgical Risk Assessment (QMRA) represents a majr step frward in terms f mdelling Salmnella in pigs frm farm t cnsumptin as it takes int accunt the variability between and within EU Member States (MSs). Arund 10-20% f human Salmnella infectins in EU may be attributable t the pig reservir as a whle. Frm the QMRA analysis it appears that an 80% r 90% reductin f lymph nde prevalence shuld result in a cmparable reductin in the number f human cases attributable t pig meat prducts. Theretically, accrding t the QMRA the fllwing scenaris appear pssible (a) by ensuring that breeder pigs are Salmnella-free a reductin f 70-80% in high prevalence MSs and 10-20% in lw prevalence MSs can be freseen; (b) by feeding nly Salmnella-free feedstuffs, a reductin f 10-20% in high prevalence MSs and 60-70% in lw prevalence MSs can be freseen; and (c) by preventing infectin frm external surces f Salmnella (i.e. rdents and birds) a reductin f 10-20% in slaughter pig lymph nde prevalence can be freseen in bth high and lw prevalence MSs. A hierarchy f cntrl measures is suggested - a high prevalence in breeder pigs needs t be addressed first, fllwed by cntrl f feed and then cntrl f envirnmental cntaminatin. Als accrding t the QMRA, fr each MS, a reductin f tw lgs (99%) f Salmnella numbers n cntaminated carcasses wuld result in a 60-80% reductin f the number f human salmnellsis cases attributable t pig meat cnsumptin. The cntrl f Salmnella in pig reservir in the EU is a reasnable bjective. The EU Salmnella cntrl strategy in pigs shuld be cntinuusly evaluated t identify pssible imprvements. KEY WORDS Salmnella, pigs, pig meat, QMRA, cntrl, preventin, risk assessment, epidemilgy 1 On request frm the Eurpean Cmmissin, Questin N EFSA-Q , adpted n 11 March Panel members: Olivier Andreletti, Herbert Budka, Sava Buncic, Jhn D Cllins, Jhn Griffin, Tine Hald, Arie Hendric Havelaar, James Hpe, Günter Klein, James McLauchlin, Winy Messens, Christine Müller-Graf, Christphe Nguyen-The, Birgit Nerrung, Luisa Peixe, Miguel Priet Maradna, Antnia Ricci, Jhn Sfs, Jhn Threlfall, Ivar Vågshlm, Emmanuel Vanpdenbsch. Crrespndence: bihaz@efsa.eurpa.eu 3 Acknwledgement: The Panel wishes t thank the members f the Wrking Grup n a Quantitative Micrbilgical Risk Assessment f Salmnella in slaughter and breeder pigs fr the preparatin f this pinin: Pierre Clin, Aline De Keijer, Françis Madec, Karsten Neckler, Mez Sanaa, Yves Van der Stede, Pirkk Tuminen, Ivar Vågshlm, and Martin Wierup and EFSA s staff member Michaela Hempen fr the supprt prvided t this EFSA scientific utput. Suggested citatin: EFSA Panel n Bilgical Hazards; Scientific Opinin n a Quantitative Micrbilgical Risk Assessment f Salmnella in slaughter and breeder pigs.. [80 pp.]. di: /j.efsa Available nline: Eurpean Fd Safety Authrity,

2 SUMMARY Fllwing a request frm the Eurpean Cmmissin, the Panel n Bilgical Hazards was asked t deliver a scientific pinin n a Quantitative Micrbilgical Risk Assessment (QMRA) f Salmnella in slaughter and breeder pigs. The assessment wuld prvide the input fr a future cst/benefit analysis f setting a target fr reductin in slaughter pigs at EU level. EFSA cmmissined a QMRA mdelling the pig meat fd chain frm farm t frk. The QMRA mdel was based n input data frm the baseline studies f Salmnella in breeder and slaughter pigs, and ther relevant data. The QMRA represents a majr step frward in terms f mdelling Salmnella in pigs frm farm t cnsumptin as it takes int accunt the variability between and within EU Member States (MSs). Transmissin f Salmnella was analysed using the individual pig as the unit f interest. There are data gaps and critical assumptins in the mdel, and these shuld be carefully cnsidered when interpreting the results f the mdel. The fractin f human salmnellsis cases attributable t Salmnella in pigs and pig meat will vary cnsiderably between MSs and will mainly depend n i) the Salmnella ccurrence (prevalence and numbers) in pigs and pig meat, ii) cnsumptin patterns and preferences and iii) the relative imprtance f ther Salmnella surces. Frm the descriptive and cmparable analysis f the servar distributin in animal surces and humans, a cautius assessment wuld be that arund 10-20% f human Salmnella infectins in EU may be attributable t the pig reservir as a whle. Hwever, the use f this estimate necessitates cautin due t the lack f MS-specific data n the distributin f servars in humans. Frm the QMRA analysis it appears that an 80% r 90% reductin f lymph nde prevalence shuld result in a cmparable reductin in the number f human cases attributable t pig meat prducts. Breeder pig herd prevalence is a majr determinant f slaughter pig lymph nde prevalence at EU level. The imprtance appears t be mre bvius in high prevalence cuntries as a 90% reductin f the breeder pig herd prevalence culd theretically result in a reductin in an rder f magnitude f tw thirds f slaughter pig lymph nde Salmnella prevalence. The majr surces f infectin fr breeder pigs are the same as fr slaughter pigs; infected incming pigs and Salmnella cntaminated feed, plus ther external and internal surces. Salmnella cntrl in breeder pig farms need t fcus n the fllwing key cntrl measures (1) cntrl f Salmnella in nucleus and multiplier herds; (2) cntrl f Salmnella in incming pigs (knwledge f Salmnella status); (3) cntrl f Salmnella in feed; and (4) bisecurity prgrams shuld include the cntrl f Salmnella. T achieve cntrl f Salmnella in slaughter pigs the tw majr surces shuld be cntrlled: Salmnella-infected breeder pig herds, and Salmnella-cntaminated feed. Theretically, accrding t the QMRA fllwing scenaris appear pssible (a) by ensuring that breeder pigs are Salmnella-free a reductin f 70-80% in high prevalence MSs and 10-20% in lw prevalence MSs can be freseen; (b) by feeding nly Salmnella-free feedstuffs, a reductin f 10-20% in high prevalence MSs and 60-70% in lw prevalence MSs can be freseen; and (c) by preventing infectin frm external surces f Salmnella (i.e. rdents and birds) a reductin f 10-20% in slaughter pig lymph nde prevalence can be freseen in bth high and lw prevalence MSs. A hierarchy f cntrl measures is suggested - a high prevalence in breeder pigs needs t be addressed first, fllwed by cntrl f feed and then cntrl f envirnmental cntaminatin. Als accrding t the QMRA, fr each MS, a reductin f tw lgs (99%) f Salmnella numbers n cntaminated carcasses wuld result in a 60-80% reductin f the number f human salmnellsis cases attributable t pig meat cnsumptin. A reductin f ne lg wuld result in a 0-40% reductin f human cases. This culd be achieved thrugh measures preventing direct and/r indirect faecal cntaminatin during transprt, lairage and, particularly, slaughter and dressing prcesses; and/r by effective carcass decntaminatin. 2

3 Cntrl f Salmnella in pig meat as a public health prblem shuld be based n the individual MSs situatins and include cmbinatins f fllwing interventins: Salmnella-free (lw risk) breeder pigs, Salmnella-free feed, cleaning-disinfectin between batches bth n-farm and during lairage, avidance f faecal cntaminatin during slaughter and decntaminatin f the carcasses. Efficient vaccinatin will als be useful t cntrl Salmnella n farm, but might interfere with the interpretatin f serlgical test results in mnitring/surveillance prgrammes. The QMRA results culd give sme guidance n apprpriate cmbinatins. Frm the current evidence, it wuld appear that specific slaughterhuse interventins are, at present, mre likely t prduce greater and mre reliable reductins in human illness, at least in a shrter timeframe, than can be achieved at the farm in high prevalence MSs. Hwever, the hypthetical reductins and multiple interventins investigated with the current risk assessment mdel suggest that MSs can achieve mre effective reductins in human cases by targeting bth farm and slaughterhuse. MSs shuld have the pssibility t assess their natinal pig meat fd chains using this QMRA mdel. The slaughterhuse remains a critical step f the pig meat chain in respect t pig and carcass cntaminatin and numerus aspects (e.g. airbrne transmissin f Salmnella in the abattir) still remain unknwn. Therefre studies need t be perfrmed t prperly assess the ways carcasses becme cntaminated. The cntrl f Salmnella in pig reservir in the EU is a reasnable bjective. The EU Salmnella cntrl strategy in pigs shuld be cntinuusly evaluated t identify pssible imprvements. 3

4 TABLE OF CONTENTS Abstract... 1 Summary... 2 Table f cntents... 4 Backgrund as prvided by the Eurpean Cmmissin... 6 Terms f reference as prvided by the Eurpean Cmmissin... 6 Assessment Intrductin Interpretatin f the terms f reference Rles f QMRA cnsrtium, BIOHAZ Panel and WG, and the benefit cst analysis cntractr General cnsideratin n Salmnella and salmnellsis Salmnella infectins in humans Slaughter f Salmnella infected pigs and impact n human health Pathgenesis and dynamics f Salmnella infectin in pigs Diagnstic aspects (bacterilgy, serlgy) Review f relevant risk assessments, surces attributin, interventin studies, and EFSA pinins Risk assessments Surce attributins Interventin studies EFSA pinins Summary f Cnsrtium Reprt Review f mdelling chices, assumptins and data gaps General remarks Impact f mdelling chices and assumptins Cluster analysis definitin f EU regins and selectin f representative MSs within each regin Parameterisatin fr the different mdules (farm transprt & lairage slaughterhuse preparatin & cnsumptin) Sensitivity Analysis and Uncertainty Analysis Interventin analysis Data gaps and assumptins The pre-harvest farm stage Transprt and lairage The slaughterhuse The cutting plant stage Preparatin and cnsumptin f pig meat Dse-respnse (hazard characterisatin) and human resistance t illness issues Imprt and exprt, and trade within EU f pigs and pig meat Cnclusin abut the data gaps and assumptins Answers t the terms f reference (TOR) Slaughter pigs Relative cntributin f Salmnella infectins in slaughter pigs n cases in humans The effect f reductin f Salmnella prevalence in pigs n human Salmnella risk Surces f infectin fr fattening pigs at farm level Reductin f prevalence in slaughter pigs by cntrl measures at farm level (pre-harvest stage) Impact f transprt, lairage and slaughter prcess n cntaminatin f carcasses Expected reductin f Salmnella cases in humans by cntrl measures during transprt, lairage and slaughter Cnsideratin f multiple interventins Breeder pigs

5 Relative cntributin f Salmnella infectins in breeder pigs n Salmnella prevalence in slaughter pigs Expected reductin f Salmnella prevalence in slaughter pigs by reductin f prevalence in breeder pigs Surces f infectin fr breeder pigs at farm level Reductin f prevalence in breeder pigs by cntrl measures References Appendices A. Suggestins fr cntrl measures B. Technical Mdel Glssary

6 BACKGROUND AS PROVIDED BY THE EUROPEAN COMMISSION A ttal f 192,703 human cases f salmnellsis were reprted in the EU in , fd being the main surce f infectin. It is estimated that several thusand peple die each year in the EU due t salmnellsis. Eggs, egg prducts, pultry meat and pig meat are the main surce f utbreaks in humans frm prducts f animal rigin. Regulatin N 2160/ lays dwn prvisins fr the cntrl f Salmnella and ther specified fd-brne agents. The scpe f the Regulatin is limited t agents which pse a public health cncern. The Regulatin requires the setting f Cmmunity targets fr the reductin f the prevalence f znses and zntic agents at the level f primary prductin and where apprpriate, at ther stages f the fd chain. Target setting in pultry ppulatins (breeding hens, laying hens, brilers and turkeys) is nging. Hwever, the current prvisins als require the setting f targets fr Salmnella in live pigs within a fixed time schedule. Befre defining a Cmmunity target, an analysis f its expected csts and benefits must be prvided. In view f this future cst/benefit analysis, it seems apprpriate t carry ut quantitative risk assessments n Salmnella in slaughter and breeder pigs. In accrdance with Article 15 f Regulatin (EC) N 2160/2003, EFSA shall be cnsulted befre a target fr reductin is set. Therefre, EFSA, in particular its Panel n Bilgical Hazards, is requested t carry ut this quantitative risk assessment. The cst/benefit analysis itself is nt part f this mandate. Infrmatin n Salmnella prevalence and its risk factrs in the pig ppulatins is needed t carry ut the risk assessment. In this regard, baseline studies have been scheduled in rder t btain cmparable data n the prevalence and risk factrs in pigs in all Member States (MSs). EFSA is invlved in the drafting f the technical specificatins f the baseline studies and in the assessment f the results. Data n epidemilgical trends may be cllected frm the annual reprts f the Member States, drafted in accrdance with the prvisins in Directives 92/117/EEC 6 and 2003/99/EC 7. At the request f the Cmmissin, risk factrs and cntrl ptins fr Salmnella in pigs were als addressed in the Opinin f the Scientific Panel n Bilgical Hazards related t Risk assessment and mitigatin ptins f Salmnella in pig prductin 4. Hwever, quantitative evaluatins are nly briefly cnsidered in this pinin. TERMS OF REFERENCE AS PROVIDED BY THE EUROPEAN COMMISSION The Eurpean Fd Safety Authrity is asked t carry ut a quantitative risk assessment n Salmnella in slaughter and breeder pigs. Slaughter pigs The bjective f this request is t carry ut a quantitative assessment f the public health risk f the presence f Salmnella in slaughter pigs, including a quantitative estimatin f the risk factrs and the effect f mitigatin ptins. The assessment shuld prvide the input fr a future cst/benefit analysis f setting a target fr reductin in slaughter pigs at EU level. A baseline study t cllect cmparable infrmatin n the prevalence f Salmnella in slaughter pigs in all Member States will be carried ut frm Octber 2006 until September 2007 in accrdance with Decisin 2006/668/EC 8. The technical specificatins were based n EFSA s prpsal in Annex III t the pinin f the BIOHAZ Panel n Salmnella in pigs and invlve bacterilgical analyses f ilecaecal lymph ndes at slaughter and serlgy n meat juice. The Cmmunity Reference Labratry 4 The EFSA Jurnal (2006), 341, The numbers have been updated in the fllwing reprts. 5 OJ L 325, , p. 1. Regulatin as amended by Cmmissin Regulatin (EC) N 1003/2005 (OJ L 170, , p. 12) 6 OJ L 62, , p. 38, Directive as last amended by Regulatin(EC) N 806/2003 (OJ L 122, , p. 1) 7 OJ L 325, , p OJ L 275, , p. 51 6

7 intends t als make cmparative studies n different serlgical tests in Prevalence data frm all Member States based n these tw analyses seem therefre the mst apprpriate reference data if targets fr reductin are cnsidered. Using infrmatin frm the baseline study, the data mentined in sectin 1 and any ther infrmatin cnsidered relevant, a quantitative estimatin at Cmmunity level is requested f: the relative cntributin f Salmnella infectins in slaughter pigs n Salmnella cases in humans. If an estimatin f the influence f the prevalence f Salmnella in pigs at slaughter n human cases is nt pssible within the indicated time schedule, the influence n Salmnella prevalence in pig meat at retail shuld be estimated; the expected reductin f Salmnella cases in humans (r pig meat at retail) by a reductin (e.g. 5- r 10-fld) f Salmnella prevalence in slaughter pigs (based n bacterilgy in lymph ndes r serlgy at slaughter); the surces f infectin fr fattening pigs at farm level; the reductin f the prevalence in slaughter pigs by the mst imprtant ptential treatments r cntrl measures at farm level: the impact f transprt, lairage and slaughter prcesses n cntaminatin f carcasses; the expected reductin f Salmnella cases in humans (r pig meat) by the mst imprtant ptential cntrl ptins during transprt, at lairage r during the slaughter prcess. All sertypes in pigs that are f human health significance shuld be cnsidered tgether. Breeder pigs The bjective f this request is t carry ut a quantitative assessment n the risk f the presence f Salmnella in breeder pigs as a surce f infectin fr slaughter pigs, including a quantitative estimatin f risk factrs and the effect f mitigatin ptins. The assessment shuld prvide the input fr a future cst/benefit analysis f setting a target fr reductin in breeder pigs at EU level. A baseline study t cllect cmparable infrmatin n the prevalence f Salmnella in breeder pigs in all Member States is scheduled frm Octber 2007 until September EFSA has been requested t prpse technical specificatins fr such a baseline study. Using infrmatin frm the baseline study and any ther infrmatin cnsidered relevant, a quantitative estimatin at Cmmunity level is requested f: the relative cntributin f Salmnella infectins in breeder pigs n Salmnella prevalence in slaughter pigs (based n bacterilgy in lymph ndes r serlgy at slaughter); the expected reductin f Salmnella prevalence in slaughter pigs (based n bacterilgy in lymph ndes r serlgy at slaughter) by a reductin (e.g. 5- r10-fld) f Salmnella prevalence in breeder pigs; the surces f infectin fr breeder pigs and piglets at farm level; the reductin f the prevalence in breeder pigs and piglets by the mst imprtant ptential treatments r cntrl measures at farm level. All sertypes in pigs that are f human health significance shuld be cnsidered tgether. 7

8 The Cmmissin will frward the results f the baseline study befre the end f It is requested that the quantitative assessment is carried ut befre the end f June , allwing the Cmmissin t carry ut a cst/benefit analysis and set a target fr reductin within its legal cnstraints. 9 The Eurpean Cmmissin has agreed t pstpne the date fr delivery f the scientific pinin t 31 March

9 ASSESSMENT 1. Intrductin The data cllected by the Cmmunity system fr znses mnitring shw that salmnellsis remains a very imprtant zntic disease in humans with 131,468 cnfirmed cases in the EU in 2008 (ntificatin rate 26.4 per 100,000 ppulatin), tpped nly by campylbacterisis with 190,566 cnfirmed cases. The ttal number f reprted human salmnellsis cases in the EU has decreased steadily by several thusand cases annually since 2004, frm 195, cases in 2004 t 133,258 in The reprting f cnfirmed human salmnellsis cases in 2008 represents a 13.5% decrease frm 2007 in Member States (MSs) (EFSA, 2010). Salmnella was the mst cmmn reprted causative agent fr fd-brne utbreaks in the EU in 2008, being respnsible fr 35.4% f all reprted utbreaks. A ttal f 490 verified Salmnella utbreaks were reprted by MSs, crrespnding t 26.0% f the ttal reprted Salmnella utbreaks. 7.1% f human cases caused by Salmnella were attributed t pig meat and prducts (12.2% f human cases caused by S. Typhimurium and 2.2% f cases caused by S. Enteritidis were attributed t pig meat and prducts). In cntrast, Campylbacter caused 9.2% f all reprted utbreaks and 2.4% f verified utbreaks (EFSA, 2010). Table 1: Number f cnfirmed salmnellsis cases in humans (EFSA, 2010) Number f cnfirmed cases in the EU , , , ,468 EFSA and previusly the SANCO Scientific Cmmittee n Veterinary Measures relating t Public Health (SCMVPH) have issued several pinins n Salmnella during the last 15 years, such as the pinins n fd brne znses, Salmnella and its main surces, Salmnella in the pultry and pig meat fd chains. Salmnella-reducing cntrl measures early in the fd chain may nt always reduce the public health risks. This is because Salmnella can multiply and survive alng the fd chain, behaving as an infectius agent in the pre-harvest stage and as a fd cntaminant in the harvest and pst-harvest stages. T assess the impact f Salmnella targets and the public health risk measured as incidence f human salmnellsis, EFSA cmmissined a quantitative micrbial risk assessment (QMRA) frm a cnsrtium cnsisting f RIVM, Fd DTU and VLA, mdelling the pig meat fd chain frm farm t frk. The QMRA mdel shuld be based n input data frm the baseline studies f Salmnella in breeder and slaughter pigs, and ther relevant data. This is ne f the first cmprehensive farm-t-frk mdels where the cnsumer risk fr Salmnella in pig meat has been explicitly mdelled at the EU level. This QMRA represents a majr step frward in terms f mdelling Salmnella in the pig meat fd chain. The challenge has been t derive a relevant mdel, i.e. a set f equatins given current knwledge f the pig meat fd chain, and thereafter t use the mdel equatins t make valid inferences n the effects f Salmnella cntrl measures within the EU pig meat fd chain. 10 This number (195,946 cases f human salmnellsis) is higher than given in the backgrund in this pinin (192,703 cases) since the number f human cases is cntinuusly updated as mre infrmatin becmes available. 9

10 The Salmnella risk resulting frm the slaughtering f breeder pigs (sws, bars) was nt cnsidered in the mdel. Furthermre, the QMRA did nt lk at the prductin system f breeder pigs. The breeder pig prevalence is nly used as a variable fr surce f infectin f slaughter pigs. The QMRA mdel was develped as a generic mdel. It is flexible enugh t be adpted and used by any MS, using their specificatins and data, if available. A further refinement f the mdel wuld be t mdel the impact f the breeding pyramid in pig prductin. At the tp in this pyramid (Figure 1) are elite breeding, r nucleus, herds that fllw special selectin prcedures, deliver bars fr prductin f semen at bar statins. These herds can als deliver purebred bars and gilts t all ther prductin hldings (farrw-t-finish, farrw-tweaner and farrw-t-grwer hldings). Beneath this elite breeding there are multiplier herds. These herds deliver replacement animals t all prductin herds. The latter herds, ften referred t as cmmercial, r piglet-prducing herds, prduce piglets and keep them until weaning (farrw-t-weaner), until the first stage f fattening (farrw-grwer hldings) r cvering the whle prductin phase (farrw-t-finish). The latter and the weaner-t-finish hldings as well as the finisher hldings prduce pigs that are called in this reprt slaughter pigs and are sent t slaughter at the end f the grwing/finishing perid. Sme f the pigletprducing herds, can als have units fr slaughter pigs, and are usually called integrated herds r farrw-t-finish herds. Overview f the pig breeding and prductin hldings included in the EU MRSA baseline survey in breeder pigs, Weaner-t-finish and finisher hldings are nt cvered by the survey (EFSA, 2009a) 11 The gains frm cntrlling Salmnella in pig meat alne might be lwer cmpared t cntrlling Salmnella all alng the fd chain, i.e. pre-harvest and pst-harvest. 11 Please refer t Glssary at end f reprt fr definitins. 10

11 1.1. Interpretatin f the terms f reference The current pinin is based n the QMRA cnsrtium s reprt, findings in previus EFSA/EU pinins, ther risk assessments, the scientific literature, and expert pinins. In this pinin slaughter pigs are synnymus with fattening pigs, and breeder pigs with breeding pigs. Furthermre, the terms Salmnella servars and sertypes are used synnymusly in this pinin. The issue f antimicrbial resistance in Salmnella was nt dealt with in this pinin, as it was utside the terms f reference (TOR). It shuld be nted that lymph nde prevalence f Salmnella des nt tell the same stry as prevalence f antibdies t Salmnella. Lymph nde prevalence represents the current status f infectin amngst pigs while prevalence f antibdies (serlgy) represents the histry f infectins amngst pigs. The fcus f this pinin is n the incidence f human Salmnella infectins. Other health parameters such as disease burden (disability adjusted life years - DALY) and mrtality are assumed t be prprtinal t the incidence. Therefre the public health risk is measured as the number f Salmnella cases and relative changes in such number. This assumptin seems reasnable and is supprted by findings f Haagsma et al. (2008). In this pinin it is assumed that all relevant EU legislatin fr animal health, welfare and fd safety are cmplied with. This pinin des nt cnsider the ecnmical benefits and csts as they are utside the EFSA remit and are cnsidered separately, as the DG Health and Cnsumers has cmmissined a benefit cst analysis. The QMRA mdel did nt cnsider the effect f trade f pig meat, pig meat prducts and live pigs within the EU r with third cuntries Rles f QMRA cnsrtium, BIOHAZ Panel and WG, and the benefit cst analysis cntractr EFSA received the request frm the Eurpean Cmmissin (EC) t carry ut a quantitative risk assessment n Salmnella in breeder and slaughter pigs. The task was given t EFSA s Scientific Panel n Bilgical Hazards. A wrking grup (WG) was established t draft the scientific pinin fr cnsideratin by the Bilgical Hazards Panel. In rder t supprt the WG, an Article 36 call was launched and this led t the grant being awarded t a cnsrtium (VLA, RIVM, Fd-DTU), hereafter referred t as the QMRA cnsrtium. The QMRA cnsrtium s task was t carry ut a quantitative micrbial risk assessment as specified in the grant agreement based n the results f the baseline studies f slaughter and breeder pigs. In additin, DG Health and Cnsumers has cmmissined a benefit cst analysis f pssible cntrl measures in the pig meat fd chain as a separate exercise t be undertaken by anther cntractr. Due t delays in cmpleting the baseline study n Salmnella in breeder pigs it has been necessary t wrk in parallel instead f sequentially. Therefre with a view t facilitate the wrk prgress and respect the deadlines there has been an pen exchange f infrmatin between thse ding baseline studies, the EC representatives, EFSA secretariat, Panel n Bilgical Hazards and its wrking grup, the QMRA cnsrtium, and the EC cntractr ding the benefit cst analysis. 11

12 2. General cnsideratin n Salmnella and salmnellsis 2.1. Salmnella infectins in humans Salmnella infectins in humans may result in distinct clinical syndrmes, including acute gastrenteritis, fever, and bacteraemia with r withut fcal extra-intestinal infectins and reactive arthritis (Chen et al., 1987). Haagsma et al. (2008) investigated the disease burden f salmnellsis in the Netherlands, f which 697, 17 and 33 Disability Adjusted Life Years (DALYs) were attributed t gastrintestinal disease, reactive arthritis and inflammatry bwel syndrme, respectively. The crrespnding number f cases f gastrintestinal disease, reactive arthritis and inflammatry bwel disease was 35,400, 460 and 7 cases, respectively. In line with previus EFSA pinins all Salmnella servars are cnsidered as representing a ptential public health hazard. Currently there is n way f predicting in the labratry whether a Salmnella servar represents a public health hazard r nt. Nevertheless, there is evidence that sme Salmnella servars are mre invasive (Wllin, 2007) and that sme are mre persistent thrughut the fd chain. The frequency rankings f Salmnella servars fund in feed, live pigs, pig carcasses and humans are nt the same. This culd reflect the pssibility that different servars have a different virulence r different ability t survive and multiply alng the fd chain. There is a need t develp science-based criteria befre attempting t differentiate between Salmnella servars. When mre knwledge f differences in virulence f Salmnella servars and their ability t survive and multiply in the fd chain is available, pssibilities fr further refinements f the current mdel will arise Slaughter f Salmnella infected pigs and impact n human health Finisher pigs may harbur Salmnella in several tissues, especially the digestive tract including assciated lymph ndes and als n the cntaminated skin. Subclinically infected carriers may be a risk factr fr hrizntal transmissin via cntaminated faeces, e.g. during transprtatin t the abattir r while waiting in the lairage befre slaughter (Vieira-Pint et al., 2005). Several studies have attributed stress factrs induced by transprt and feed withdrawal t an increased shedding f Salmnella frm Salmnella-infected pigs (Isaacsn et al., 1999; Mrgan et al., 1987). A translcatin f Salmnella t muscular tissue was bserved in slaughtered pigs after expsure t severe stress (Fehlhaber, 2003; Fehlhaber and Alter, 1999). On the ther hand, accrding t ther experimental studies, transprtatin f pigs had n influence n the distributin patterns and numbers f Salmnella Typhimurium in rgans r faecal samples in infected pigs (Marg et al., 2001; Scherer et al., 2008). The rle f sub-clinically infected pigs fr hrizntal transmissin via cntaminated faeces during transprtatin t the abattir r while waiting in the lairage is highlighted in all these studies. Variatins in the number f Salmnella carriers related t the transprt stress may be explained by differences in the experimental design applied fr the study (e.g. number f pigs examined, use f Salmnella strain, transprt time and cnditins). At slaughter the tnsils are frequently fund t cntain high numbers f S. Typhimurium and may play an imprtant rle in the invasin and disseminatin f Salmnella (Fedrka-Cray et al., 1994). A significant crrelatin was bserved between prevalence f Salmnella in the tnsils and psitive carcasses during slaughter (Swanenburg et al., 1999). In a lngitudinal study n experimental infectin with S. Typhimurium definitive phage type (DT) 104 in fattening pigs, the highest level f Salmnella clnisatin was detected in tnsils, jejunal and ilecaecal lymph ndes at slaughter (Scherer et al., 2008). The presence f S. Typhimurium in mandibular lymph ndes may als pse a risk f crsscntaminatin due t incisin during sanitary inspectin and prcessing. Once a prcessing line is cntaminated, Salmnella can be islated frm the machinery, hands f wrkers, knives and carcasses (Berends et al., 1996; Small et al., 2006). Frm 1990 t arund 2000, the multiresistant S. Typhimurium DT 104 was, in sme MSs, ne f the mst frequently islated sertypes frm pig meat (Pppe et al., 2002) which des nt usually cause 12

13 clinical disease in pigs (van der Wlf et al., 1999). Nevertheless, sub-clinically infected carriers pse a reservir f infectin that is f cnsiderable imprtance in human health (Olsen et al., 2001) Pathgenesis and dynamics f Salmnella infectin in pigs Results f clinical studies in pigs demnstrate that S. Chleraesuis infectin can result in septicaemia and t enterclitis, pneumnia and/r hepatitis as a cnsequence f bacteremia whereas infectin with S. Typhimurium may smetimes cause enterclitis and diarrhea (Reed et al., 1986; Schwartz, 1999; Wd and Rse, 1992). Other experimental investigatins in weaning piglets using an ral dse f 10 9 clny-frming units (cfu) S. Typhimurium led t clinical signs such as fever and vmiting at the early stage f infectin (Scherer et al., 2008; Szab et al., 2009) but als the absence f clinical signs (Kampelmacher et al., 1969). Differences in the clinical utcme after expsure may be due t servar r strain specific differences (Huehn et al., 2009) in virulence and/r cnstitutin f pigs such as susceptibility and predispsitin. In tw studies (Osterberg et al., 2009; Osterberg and Wallgren, 2008) pigs were inculated with the fllwing servars: Typhimurium, Derby, Yruba r Cubana, at dses f 0.65*10 9, 10 6 and 10 3 cfu, respectively. The results indicated large differences in serlgical respnses and the status f Salmnella infectin. Bth servar and number f Salmnella inculated were cnsidered t be imprtant factrs. Fllwing Salmnella infectin in pigs, pathgenesis is characterized by three phases: (1) clnisatin f intestines, (2) invasin f entercytes, and (3) bacterial disseminatin t lymph ndes and rgans (Berends et al., 1996). Sme Salmnella servars are able t invade the tnsils 30 minutes after ral uptake/cntact with the cntaminatin surce and within few hurs (2h t 3h) they can clnize the mandibular lymph ndes, cln, caecum, and ilecaecal lymph ndes (Hurd et al., 2001a). After experimental infectin with Salmnella Typhimurium DT104, pigs excreted Salmnella during tw weeks pst infectin, thereafter shedding rate in faeces declined and became intermittent until the end f the five mnths fattening perid (Scherer et al., 2008). Several rgans including the tnsils serve as imprtant sites fr persistence f Salmnella (Fedrka-Cray et al., 1994; Lynachan et al., 2004). Since Salmnella is able t survive and prliferate in phagcytes and leuccytes, translcatin t gut assciated lymphid tissue is pssible (Reed et al., 1986; Wells, 1990). The immune respnse in the intestine f the hst is determined by a number f cmplex mechanisms including factrs such as immune cell interactins with bacteria and their prducts (Bailey et al., 2001). In several studies with pigs challenged with Salmnella, the develpment f the humral immune respnse in serum was investigated. After experimental infectin with S. Typhimurium DT 104, Salmnella-specific IgG antibdies are detected in the majrity f pig sera between day 22 and 39 pst infectin (Szab et al., 2008). Mst publicatins n pathgenesis in pigs are n servars knwn t be pathgenic t pigs, like S. Chleraesuis, while fr utbreaks (human cases) attributed t pig meat the servar Typhimurium is mst frequently islated. Generalizing frm data based n utbreaks f S. Typhimurium may lead t a biased estimatin f human health risk (verestimatin), since S. Typhimurium and in particular, the utbreak islates, are thught t be mre virulent (see discussin in sectin 5.3.6) Diagnstic aspects (bacterilgy, serlgy) In an earlier EFSA pinin (EFSA, 2006), the principles, advantages, disadvantages, and relevance f bacterilgical and immunlgical analysis methds have been described. The bjectives f the tw appraches are very different and the chice f diagnstic methd t be used will depend n the actual situatin and the questins that are required t be answered. The actual presence f Salmnella in pigs can be directly diagnsed at the abattir r at the farm level by islating Salmnella with varius established bacterilgical methds (Christensen et al., 2002). Since cnventinal culture methds are labrius, time cnsuming and cstly, serlgical techniques 13

14 using ELISA based n lipplysaccharide antigens have prven t be practical and cst effective methds and therefre mre suitable fr rutine testing f herd status at slaughter (Nielsen et al., 1995; Prux et al., 2000). Serlgical methds indicate previus expsure t Salmnella but cannt differentiate between acute r chrnic/sub-clinical infectin f an individual pig r if ser-psitive pigs are currently carrying r shedding Salmnella r have eliminated the infectin. Recently-infected pigs are als nt identified befre sercnversin. Therefre, serlgical testing is less suitable fr individual animals but apprpriate fr screening purpses at herd level (Nllet et al., 2005; Wng et al., 2003). The mnitring systems applied in Salmnella surveillance prgrams fr fattening pigs are usually based n serlgical examinatin by means f ELISA. The results are ften used t classify herds int e.g. three categries, herds with lw, mderate r high prevalence f antibdy-psitive pigs (Musing et al., 1997). The criteria fr the classificatin rules (risk farm versus nn r lw risk farm) as well as the sampling schemes can differ significantly between MSs. Fllwing infectin with Salmnella, there is a high faecal excretin in pigs within tw weeks pst infectin and the peak f bacterial excretin in faeces is fllwed by an immune respnse after a further 1-2 weeks (Nielsen et al., 1995). Thus, when pig sera are tested fr specific antibdies in the early stage f infectin, negative results can ccur due t delayed sercnversin. Cnversely, during the chrnic stage f infectin which cvers the main part f the life span f a fattening pig, animals shw a higher rate f ser-psitive animals cmpared t a lwer rate f pigs shedding Salmnella in faeces (Scherer et al., 2008). The intrductin f Salmnella-infected pigs (e.g. gilts r bars fr breeding herds, piglets fr grwt-finishing farms) is an imprtant external surce. Hwever the challenge t implement cntrl measures is t ensure that incming pigs are Salmnella-free. The reliable detectin f infected pigs (individual level r grup/herd level) by the use f bacterilgical methds remains labrius and is time cnsuming. Available methds, when nt used in repeated testing, have a lw sensitivity when used n individual animals, but are mre apprpriate when used n a herd r grup level/herd f rigin. The sle use f serlgy is nt accurate and ther tests (e.g., n faeces) are needed (Davies et al., 2003). Hwever judicius use f testing at herd level ver extended perids (mnths, years) cmbined with knwledge abut bisecurity level in the herd and its disease histry might allw cnclusins abut the Salmnella status f pigs. Quality assurance has t be applied in rder t prduce results that can be cmpared with cnfidence between labratries/cuntries. Results btained using bacterilgical methds and immunlgical methds cannt be cmpared directly. Since the same labratry was analysing results frm baseline studies f breeder pigs and slaughter pigs, it is pssible that a part f the crrelatin bserved between slaughter pig and breeder pig prevalence in a MS may be attributable t the sampling and prcessing f samples in the natinal labratry. The magnitude f this effect cannt be assessed at this pint in time. The purpse f the design f baseline surveys was t minimize this srt f crrelatin. In cnclusin, it is imprtant t cnsider the dynamics f Salmnella infectins in pigs and the characteristics and bjectives f bacterilgical and/r serlgical tests, when designing surveillance r mnitring prgrams, e.g. baseline studies, and interpreting the results f these. 3. Review f relevant risk assessments, surces attributin, interventin studies, and EFSA pinins 3.1. Risk assessments Human health is usually the end-pint f zntic micrbilgical risk assessments, as fd safety and public health prtectin are the verall bjectives f micrbilgical risk analysis (Cdex Alimentarius, 1999). 14

15 Quantitative risk assessments cncerning the whle fd chain r part(s) f it have typically been mdelled as mdules, fllwing the apprach develped fr QMRAs n Salmnella in pultry (FAO/WHO, 2002; USDA, 1998). In the mdular apprach, the results f ne mdule are explited as inputs in the fllwing mdule. Bth deterministic and stchastic methds have been used. Only a few farm-t-frk QMRAs have been published n Salmnella in pig meat prductin. As with all risk assessments, they have als been targeted at addressing risk management issue(s) and may therefre be limited frm ther pints f view (Bllaerts et al., 2009). In Belgium, a QMRA mdel called METZOON assessed the risk n human salmnellsis thrugh husehld cnsumptin f fresh minced Belgian pig meat, bth pure and mixed with ther meat. This assessment started frm primary prductin (fattening herds) and ended at the pint f human illness (Bllaerts et al., 2009). It used the dse-illness mdel that was fitted by Bllaerts et al., (2008) t utbreak data f human salmnellsis taking int accunt hst susceptibility (susceptible versus nrmal ppulatin), servar and fd matrix. The authrs included this infrmatin int the farm-tfrk risk assessment in rder t estimate the annual number f Salmnella cases. The human cases were estimated mainly t be a cnsequence f undercking and t a lesser extent, crsscntaminatin in the kitchen. Delhalle et al. (2008) evaluated the ptential risk factrs f Salmnella cntaminatin f pig carcasses assciated with prductin parameters, technical facilities and methds used fr cleaning/disinfectin in the ten largest Belgian slaughterhuses. The study indicated that wrking practices such as scalding with steam, a secnd flaming after plishing, and cleaning/disinfectin f the splitter machine several times a day, were beneficial in reducing cntaminatin by Salmnella. Prductin stages after the slaughterhuse were als studied in seven cutting plants, fur minced meat plants f the fur largest retailers in Belgium using data frm the fficial Fd Agency as well as frm self-mnitring (aut-cntrl) prgrams (Delhalle et al., 2009a). Anther Belgian QMRA n human salmnellsis fllwing cnsumptin f fresh minced pig meat was cnducted by Delhalle et al. (2009b). Its main gal was t give practical ptins t reduce effectively the risk f human salmnellsis thrugh the cnsumptin f minced pig meat. In Finland, Ranta et al., (2004) assessed the cnsumer risk due t all pig meat-derived fds available t cnsumers and Salmnella prevalence in the pig meat fd chain frm slaughter pigs t cnsumptin in rder t evaluate the efficacy and ecnmics f the natinal Salmnella cntrl prgramme, as well as the influence f special guarantees 12 n cnsumer risk. In the UK, cnsumer risk regarding S. Typhimurium acquired frm pig meat, mixed meat prducts and bacn was als assessed with a farm t frk mdel by Hill et al. (2003). In Denmark, Alban et al. (2002) cmpared the number f prtins cnsumed and salmnellsis risk t cnsumers acquired frm dry-cured sausages prduced frm dmestic and imprted pig meat, and reprted that the imprted sausages were cntaminated mre than 37 times mre ften cmpared t dmestic sausages. Accrding t the Finnish QMRA, imprted pig meat and pig meat-derived fds caused as many salmnellsis cases as dmestic prducts, althugh imprts accunted fr nly 8% f the verall cnsumptin (Ranta et al., 2004). The cnsumer risk due t Salmnella-cntaminated pig meat prducts was assessed in the Abruzzi regin f Italy, revealing fresh pig meat t be an imprtant surce f human salmnellsis (Givannini et al., 2004). The study revealed that the Salmnella prevalence in fresh sausages was significantly higher than in fresh meat, indicating cntaminatin during preparatin r bacterial grwth during the manufacture and/r strage f sausages. 12 Special guarantees ( additinal guarantees until ) cncerning certain animal-derived fd prducts including fresh and minced meat frm prcine animals were admitted t Finland and Sweden at the time f their accessin t the Eurpean Unin (Cuncil Directive 94/65/EC; Cuncil Decisin 95/409/EC; Cmmissin Regulatin (EC) N 1688/2005) because f their lw Salmnella prevalence and nging natinal Salmnella prgrammes. Accrding t the regulatin, all such cnsignments have t be tested Salmnella-negative befre exprted them t these cuntries. 15

16 3.2. Surce attributins In Denmark, dmestically prduced pig meat was estimated t be the mst imprtant surce f human salmnellsis in 2008 (9%), fllwed by imprted chicken (5%) and table eggs (3%). The estimated number f cases attributed t the cnsumptin f pig meat increased three-fld cmpared t 2007 (Annymus, 2009). This increase is partly explained by the ccurrence f an unusual number f pig meat-related utbreaks in 2008 (Ethelberg et al., 2008). In recent attributin studies dne by Pires et al. (Pires, 2009; Pires et al., 2008) the prprtin f pig meat-assciated cases acquired dmestically was estimated fr fur EU cuntries: Denmark ( %), the Netherlands ( %), Sweden ( %) and UK ( %). In Finland, a mdel based n a similar type f cmparisn and initially develped fr the estimatin f salmnellsis cases due t briler meat (Maijala et al., 2005) was incrprated in the QMRA n Salmnella in the pig meat prductin chain (Ranta et al., 2004). When cmpared t ther Salmnella QMRAs, cnducted at the same time fr briler, egg and beef prductin chains, it appeared that pig meat and pig meat-derived fds were the secnd largest grup f fd prducts causing salmnellsis in cnsumers in Finland, while beef and beef-derived fds were the mst imprtant Interventin studies Mst risk assessments f the effect f different risk management ptins d nt fcus n the whle prductin chain but instead cncentrate n certain stages f the fd chain and mre clsely investigate interventins r prcessing techniques used. Assessments n the effect f different risk management ptins have been cnducted at varius levels f the fd prductin chain. A lw prevalence f Salmnella in the raw material, imprvements in singeing efficiency, and a reductin f crss-cntaminatin during degutting and handling at slaughter were cnsidered as imprtant riskreductin factrs in the slaughter prcess (Alban and Stark, 2005). The results f the Belgian QMRA shwed Salmnella reductin during plishing, evisceratin and chilling wuld be the mst effective strategies f the slaughter prcess while prcesses at the beginning f the slaughter prcess seem t have nly a limited effect (Bllaerts et al., 2010). The implementatin f gd hygiene practices (GHP) frm the transprt phase up t the cutting r retail phase cupled with a decntaminatin step at the end f the slaughter line, might reduce the prevalence f cntaminated carcasses and pig meat by as much as 50-60% (Berends et al., 1998a). Mnitring f critical pints, the cnditin and cleanliness f equipment, gd slaughtering practices, and effective cleaning and disinfectin f equipment were cnsidered as the key elements cntributing t fd safety during the slaughter prcess (Delhalle et al., 2008). In meat cutting plants and butchers shps, imprper cleaning and disinfectin, manipulatin f cntaminated materials and (re)cntaminated surfaces were evaluated as the mst imprtant risk factrs, hwever implementatin f GHP did nt reduce daily crss-cntaminatin by mre than abut 10% (Berends et al., 1998b). In additin, GHP in abattirs and meat cutting plants was als cnsidered t have nly marginal effects n the ccurrence f Salmnella in final prducts, accrding t the studies f Gnzales Barrn et al.(2009). In that study final rinsing and chilling f carcasses was fund t have a cnsiderable influence. Accrding t sme risk assessments, the mst effective measures t reduce the cnsumer risk take place at slaughterhuse level and can be implemented by means f decntaminatin prcedures (Berends et al., 1998b; Bllaerts et al., 2010; Hurd et al., 2008; Smmer et al., 2003). In sme cuntries with lw Salmnella prevalence, such as Finland, Nrway and Sweden, the applicatin f pre-harvest cntrl measures has been an essential part f their Salmnella cntrl prgrammes, and is regarded as the majr reasn fr their lw prevalence status bth at the pre-harvest and pst-harvest level including pig meat (Hpp et al., 1999). An analysis f the pre-harvest fcus and 16

17 the nn acceptance f Salmnella 13 as applied in Sweden has demnstrated its advantages in public health terms, in relatin t a mre cnservative apprach (Engvall A., 1993). The Finnish cst-benefit analysis, based n the Salmnella QMRA cnducted, gave similar results (Kangas et al., 2007). The calculatins based n the Finnish risk assessments n pultry, beef, table egg and pig meat prductin chains suggest that cntrls in primary prductin play the majr rle in Salmnella risk caused t the cnsumer. In general, the cnclusins frm risk assessments will be determined by the lcal cnditins (current prevalences), bjectives f the assessment, mdel/study design and the input data used EFSA pinins The Bilgical Hazards Panel has already adpted an pinin n risk mitigatin ptins fr Salmnella in pig prductin (EFSA, 2006). The cnclusins f this pinin remain valid in general. Furthermre, the Panel adpted an pinin n surce attributin fr human salmnellsis frm meat (EFSA, 2008a). 4. Summary f Cnsrtium Reprt Under Article 36 f the Eurpean Parliament and Cuncil Regulatin (EC) N 178/2002 (EC, 2002), the Eurpean Fd Safety Authrity (EFSA) published a call fr a Quantitative Micrbilgical Risk Assessment (QMRA) n Salmnella in slaughter and breeder pigs. As a cnsequence f the bjectives prvided in this call the VLA/RIVM/Fd-DTU cnsrtium have wrked twards a full farm-t-cnsumptin QMRA. After slaughter and dressing, the QMRA fcuses n three different prducts: prk cuts, minced meat and fermented sausages. At every stage pssible the pprtunity f crss-cntaminatin is cnsidered. T describe the crss-cntaminatin the mdel needed t be highly mechanistic, which althugh it leads t a mre cmplex mdel will allw a better examinatin f interventins fr Salmnella in pigs. The aims f the QMRA were t assess: the expected reductin f Salmnella cases in humans (r pig meat at retail) by a reductin (e.g. 5- r 10-fld) f Salmnella prevalence in slaughter pigs (based n bacterilgy r serlgy at slaughter); the surces f infectin fr fattening pigs at farm level; the reductin f the prevalence in slaughter pigs by the mst imprtant ptential treatments r cntrl measures at farm level; the impact f transprt, lairage and slaughter prcesses n cntaminatin f carcasses; the expected reductin f Salmnella cases in humans (r pig meat) by the mst imprtant cntrl measures during transprt, at lairage r during the slaughter prcess. The full reprt is published n EFSA s website The nn acceptance strategy means that crrective actins shuld always be taken whenever Salmnella is fund in the fd chain

18 5. Review f mdelling chices, assumptins and data gaps Salmnella in slaughter and breeder pigs 5.1. General remarks The cnsrtium s discussin n the data gaps and assumptins used within the mdel can be fund in the QMRA reprt chapter A summary f the technical mdel appears in Appendix B t this pinin. In the prbabilistic risk assessment apprach, a first step is t identify the variables f interest and t assign a prbability distributin t each (Hamed and Bedient, 1997). The prbability distributins fr the variables are ften selected in an empirical way (Hattis and Burmaster, 1994). The degree f cnfidence in the final QMRA utputs will depend n the way the variability, uncertainty and assumptins are handled at the different risk assessment steps. The assessment f pssible ptins fr cntrl measures has t cnsider that in the pre-harvest phase the ccurrence and spread f Salmnella is the result f infected pigs, while during the harvest and pst-harvest phase the ccurrence and spread f Salmnella is the result f the influence f crss cntaminatin and pathgen grwth/reductin r disseminatin that might ccur at different links f the fd chain. During the pre-harvest phase f the pig meat prductin, there are in principle three main surces f Salmnella intrductin in slaughter pig farms. One is ingestin f cntaminated feed, the ther is expsure t Salmnella shed by Salmnella-infected pigs alng the breeding pyramid and the third is expsure t Salmnella frm ther surces f the envirnment (EFSA, 2006). During the harvest and pst-harvest phases f the fd chain the main rute f transmissin f Salmnella is crss-cntaminatin frm the carcasses f the primarily infected slaughter pigs. The QMRA assumed that all Salmnella servars equally represent a ptential public health risk as requested in the terms f reference withut any attempt at differentiating them. In a similar way, the assumptin f similar prbability f pigs acquiring Salmnella infectin frm an expsure regardless f servar was applied. Hwever Osterberg et al (Osterberg et al., 2009; Osterberg and Wallgren, 2008) fund that the dse-respnse in newly weaned pigs expsed t Salmnella may vary cnsiderably between servars Impact f mdelling chices and assumptins Accrding t the Cdex Alimentarius Cmmissin (1999) a QMRA shuld include fur steps: hazard identificatin, expsure assessment, hazard characterizatin and risk characterisatin. Originally, risk assessment techniques evlved frm txiclgical risk assessment (estimatin f N Observed Adverse Effect, Acceptable Daily intake and Tlerable Daily intake). Micrbial risk assessments are different as the amunt f expsure t micrbial pathgens is much harder t quantify as a result f ptential micrbial grwth and inactivatin. In additin, and in particular fr Salmnella, hst behaviur and hst resistance (immunity) strngly interacts with the final risk. This is what makes QMRA f infectius diseases very cmplex. In the QMRA, presented by the cnsrtium, a prbabilistic mdular risk mdel (Mdular Prcess Risk Mdel, r MPRM) as prpsed by Nauta et al. (2005) was develped, in which the fd prductin pathway fr pig meat is split up in cnsecutive mdules (farm, transprt & lairage, slaughterhuse, cutting plant, preparatin plus cnsumptin & dse respnse mdule) with the utput f ne mdule serving as input fr the next mdule. This apprach allws and facilitates building pathgen transmissin mdels, evaluatin f changes and variability in prevalence and bacterilgical cncentratins. In additin, in a MPRM, interventin analysis is pssible (and subsequently cstbenefit analysis) as changes in prevalence, cncentratin f Salmnella and unit size can be mdelled by means f the basic prcesses in micrbial (grwth and inactivatin) and fd/carcass/pig meat handling prcesses (crss cntaminatin, cutting, partitining and mixing). 18

19 In the fllwing thse mdelling chices (methdlgies) and assumptins that may influence the utcme/utput f the QMRA will be discussed and are imprtant issues will be highlighted that shuld always be kept in mind, when analysing and using the results f the QMRA and deriving related cnclusins frm them Cluster analysis definitin f EU regins and selectin f representative MSs within each regin. Fur cuntries (MS1-MS4) were selected as cases t capture the variability in the EU wide situatin. The selectin was based n a cluster analysis, (determining clusters f cuntries with similarities in pig prductin and slaughter data) using bjective criteria (rati big/small hldings, rati utput frm big/small slaughterhuses, pig meat cnsumed and relative cnsumptin f sausages) where the weight f cnsumptin was duble cmpared t the ther criteria. The methdlgy fr the cluster analysis (k-means clustering) is very gd and intended fr situatins in which all the variables are f the quantitative type. The k-means clustering (hard clustering methds) will, inevitably, lead t misclassificatins and this is especially true fr MSs near the bundaries. Therefre, different initial partitins can result in different final clusters. Other variables that culd nt be included, due t lack f data, culd have resulted in anther classificatin. The inclusin f the data n prevalence f infected carcasses and/r lymph ndes (input farm mdule) frm the baseline studies (slaughter pigs and breeder pigs) was excluded by the cnsrtium because that data was intended fr validatin f the mdel. Inclusin f baseline data was fund nt t have a large bearing n the result f the clustering. Fr these reasns, ne shuld be careful with the interpretatin f the mdel utput fr each MS separately. This is particularly imprtant if e.g., this clustering is used in rder t set targets fr prevalence reductin. Hence, setting Salmnella prevalence targets based n this clustering is neither recmmended nr intended Parameterisatin fr the different mdules (farm transprt & lairage slaughterhuse preparatin & cnsumptin) In each mdule, parameter estimatin was dne by using data, if these were available. Significant data gaps were identified fr sme case study MSs. Therefre, input parameters (distributins) frm ther cuntries were used and these estimates were kept identical fr the thers. This apprach might intrduce a bias fr sme MSs classified in ne f the fur clusters. This was especially imprtant fr the farm mdule, which served as input fr the subsequent mdules in the mdular QMRA. In the farm mdule the estimates fr large farm/small farm management parameters, thse fr the surces f infectin fr Salmnella as well as the parameters used in the transmissin mdel were derived frm limited surces (main surces used are frm ne MS nly (MS2)) and/r assumed. Thrughut the mdel, sme distributins were assumed and/r derived frm expert pinin. In this case it wuld be mre precise t include uncertainty in the defined distributins as neglecting the uncertainty arund a variable parameter might result in a t precise utput fr sme MSs and makes extraplatin and generalisatin difficult. This is especially relevant fr risk managers during target setting and/r recmmendatins fr Salmnella reductin at the different stages alng the pig meat prductin chain. Fr the transprt mdule it is clear that reducing stress (time f transprt and stcking density) wuld significantly lead t a lwer prevalence f excreting and/r cntaminated pigs. These issues are addressed in the uncertainty analysis (QMRA reprt chapter 15). In the slaughterhuse mdule, cnsiderable effrts were made t mdel the crss-cntaminatin dwn t the last detail. Due t the cmplexity f this mdule, several (hidden) assumptins had t be made and the quantitative impact f specific assumptins is nt always bvius. Fr this mdule, the same cautin must be taken regarding the parameterisatin, as estimates were derived frm limited surces and r derived frm ther than Salmnella parameters (e.g. use f the increase in Enterbacteriaceae during plishing and transfer (transmissin) parameters btained frm chicken fr the belly pening 19

20 phase in the slaughterhuse). In additin, the estimates fr the parameters fr small slaughterhuses are derived frm ne small slaughterhuse in the Netherlands and the used parameterisatins may lead t biased results fr thse cuntries having many small slaughterhuses with a different prevalence as input fr the slaughterhuse mdule. Sme f these issues are addressed in the uncertainty analysis (QMRA reprt chapter 15). Within the slaughterhuse mdule, the crss cntaminatin - the cntaminatin f a carcass (r ther unit under investigatin) by means f a secnd agent (e.g. a cutting knife, r the scalding tank), which has previusly been cntaminated by anther carcass, is mdeled and assumed t take place in discrete time. At these different slaughterhuse stages, machinery parameters are mdeled using data frm scientific literature. It is clear hwever, that the slaughterhuse envirnment varies thrughut the EU and within slaughter stages and that specific equipment and settings f the machinery is nt cnstant as such. Therefre, the variability and the uncertainty in the utcme f the slaughterhuse mdule is expected t be much larger and subsequently impact f the estimated number f human cases. The meat prduct selectin (pig meat cuts, minced meat and fermented sausages) and mdelling the crss-cntaminatin transfer parameters during the cnsumer and preparatin phase is based n the existing diversity and their differences in risk in the harvest and pst-harvest prcessing stages. Again, sme parameters were derived frm a few limited surces and may nt be applicable in all MSs Sensitivity Analysis and Uncertainty Analysis A sensitivity analysis is perfrmed t assess hw the variatin f the utput is affected by changes in the mdel inputs. The sensitivity analysis was cnducted by a ne-way analysis f variance (ANOVA) test. In cntrast, the uncertainty assciated with the parameter values was investigated in the uncertainty analysis. This ANOVA tests the parameters f the mdel that incrprate variability - the parameterized estimates, by using a statistical distributin t describe the variability against a respnse variable and nly cnsiders the variability f the parameter values which are part f the baseline mdel. In the QMRA mdel, an independent sensitivity analysis fr the farm, transprt, lairage, slaughterhuse, cutting plant and ne fr each prduct type during the preparatin and cnsumptin mdule was perfrmed. The dse-respnse mdule was nt cnsidered fr sensitivity analysis. Therefre, the results f the sensitivity analysis shuld nly be interpreted as a ne-t-ne relatinship which means that thse parameters that were fund t imprtant in the sensitivity analysis (e.g. within-batch prevalence, prbability f pigs being stressed during transprt, minced meat strage time in fridge and prbability f pigs being stressed during transprt) are imprtant nly fr the mdule in which they were implemented. Depending n the scpe and the desired level fr uncertainty assessment in a QMRA prcess, a tiered apprach (Tier 1, 2 and 3) is recmmended by EFSA (2006) and FAO/WHO (2008). The tier level shuld be prprtinate t the needs f the QMRA mdel in rder t effectively respnd t the risk management questins. Tier 1 analysis starts by treating all uncertainties qualitatively and is the simplest frm f uncertainty analysis. Tier 2 and Tier 3 are quantitative uncertainty assessment appraches. Tier 2 cnsists f the deterministic analysis f uncertainties. Different alternative pint estimates are filled in fr uncertain inputs in the assessment and their impact n the assessment utcme is calculated. The mst detailed level and resurce intensive type f uncertainty analysis is btained via a prbabilistic analysis f uncertainties (Tier 3). In this QMRA mdel the uncertainty assciated with the parameter values was analyzed by changing certain parameters t a minimum and a maximum value. The chice f the parameters and the alternative values was dne in a subjective way and the resulting prbability f illness (fr the three prducts) was cmpared with the baseline results. Therefre, the result may be biased and, in sme cases, unrealistic. In additin, the uncertainty analysis did nt allw a distinctin between the variability and uncertainty and hw this prpagates thrugh the mdel (secnd rder distributins). By identifying qualitatively, deterministically r prbabilistically uncertainties and separately frm variability, infrmatin n data gaps can be btained. In rder t take decisins, risk managers can ask 20