SURvEILLANCE FOR BSE - fao.org fileSurveillance for BSE SURvEILLANCE FOR BSE The two major...
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Surveillance for BSE SURVEILLANCE FOR BSE The two major objectives for BSE surveillance are to determine whether BSE is present in a country, and, if present, to monitor the extent and evolution of the outbreak over time. In this way, the effectiveness of control measures in place can be monitored and evaluated. However, the reported number of BSE cases in a country can only be evalu- ated within the context of the quality of the national surveillance system. Governments must allocate and expend funds to develop and implement a national surveillance programme. These costs include personnel, testing and compensation for farmers, as well as disease awareness activities. The decision to implement such a system has both positive and negative economic and political effects. Therefore, gov- ernments must have scientific justification in order to make these decisions, normally available in the form of a risk assessment. The Terrestrial Animal Health Code OIE (considered the international standard), pro- vides general guidelines for disease surveillance (OIE, 2005a) and specific guidelines for an appropriate level of BSE surveillance (OIE, 2005b). The OIE code standards for BSE are updated frequently, often on a yearly basis, thus the most recent OIE guidelines, available at http://www.oie.int/eng/normes/mcode/en_sommaire.htm, should always be used. However, BSE risk can still exist in a country even if no cases are found with surveil- lance. Surveillance aims to supplement the more comprehensive data that are provided by a risk assessment (Heim and Mumford, 2005). 1. PASSIVE SURVEILLANCE In most countries, BSE is listed as a notifiable disease, which is a basic requirement for a functioning passive (as well as active) surveillance system. However, some countries have no national passive surveillance system for BSE, or only a weak system. Until 1999, BSE surveillance in all countries was limited to the notification of clinically suspected cases by farmers and veterinarians (and others involved in handling animals) to the veterinary authorities (passive surveillance), and it was assumed that this would allow early detection of an outbreak (Heim and Wilesmith, 2000). However, because passive surveillance relies solely on the reporting of clinical suspects and is dependent on many factors, including perceived consequences on the farm and diagnostic compe- tence, it is not necessarily consistent or reliable. Underreporting is the most important constraint of a passive surveillance system for BSE. To improve reporting and allow the overall functioning of the passive system, the following minimum factors must be in place (Doherr et al., 2001): Notification: The disease must be notifiable, meaning that there is a legal requirement to report the disease to an official authority when it is suspected. The procedure for notification should be simple, and it should be clear who is responsible for what. Veteri- narians, farmers and others involved in handling animals should know what they have to do if they identify a suspect case.
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SURvEILLANCE FOR BSE
ThetwomajorobjectivesforBSEsurveillancearetodeterminewhetherBSEispresentinacountry,and, ifpresent,tomonitortheextentandevolutionoftheoutbreakovertime.Inthisway,theeffectivenessofcontrolmeasuresinplacecanbemonitoredandevaluated.However,thereportednumberofBSEcasesinacountrycanonlybeevalu-atedwithinthecontextofthequalityofthenationalsurveillancesystem.
Governmentsmustallocateandexpendfundstodevelopandimplementanationalsurveillance programme. These costs include personnel, testing and compensationforfarmers,aswellasdiseaseawarenessactivities.Thedecisionto implementsuchasystemhasbothpositiveandnegativeeconomicandpoliticaleffects.Therefore,gov-ernmentsmusthavescientificjustificationinordertomakethesedecisions,normallyavailableintheformofariskassessment.
TheTerrestrialAnimalHealthCodeOIE(consideredtheinternationalstandard),pro-videsgeneralguidelinesfordiseasesurveillance(OIE,2005a)andspecificguidelinesforanappropriatelevelofBSEsurveillance(OIE,2005b).TheOIEcodestandardsforBSEareupdated frequently,oftenona yearlybasis, thus themost recentOIEguidelines,available at http://www.oie.int/eng/normes/mcode/en_sommaire.htm, should alwaysbeused.
However,BSEriskcanstillexistinacountryevenifnocasesarefoundwithsurveil-lance.Surveillanceaimstosupplementthemorecomprehensivedatathatareprovidedbyariskassessment(HeimandMumford,2005).
1. pASSIvE SURvEILLANCEInmostcountries,BSEislistedasanotifiabledisease,whichisabasicrequirementforafunctioningpassive(aswellasactive)surveillancesystem.However,somecountrieshavenonationalpassivesurveillancesystemforBSE,oronlyaweaksystem.
Until1999,BSEsurveillanceinallcountrieswaslimitedtothenotificationofclinicallysuspectedcasesbyfarmersandveterinarians(andothersinvolvedinhandlinganimals)totheveterinaryauthorities(passivesurveillance),anditwasassumedthatthiswouldallow early detection of an outbreak (Heim and Wilesmith, 2000). However, becausepassivesurveillancereliessolelyonthereportingofclinicalsuspectsandisdependentonmanyfactors,includingperceivedconsequencesonthefarmanddiagnosticcompe-tence,itisnotnecessarilyconsistentorreliable.UnderreportingisthemostimportantconstraintofapassivesurveillancesystemforBSE.Toimprovereportingandallowtheoverall functioning of the passive system, the following minimum factors must be inplace(Doherretal.,2001):
Notification:Thediseasemustbenotifiable,meaningthatthereisalegalrequirementto report thedisease toanofficial authoritywhen it is suspected.Theprocedure fornotificationshouldbesimple,anditshouldbeclearwhoisresponsibleforwhat.Veteri-narians,farmersandothersinvolvedinhandlinganimalsshouldknowwhattheyhavetodoiftheyidentifyasuspectcase.
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DefinitionofBSE:Inordertooptimizeidentificationofallclinicalcases,thelegaldefini-tionofaBSEsuspectshouldbebroad.InseveralcountriesthelegaldefinitionforaBSEsuspectrefersonlytocattlewithneurologicalsigns,whichistoonarrowadescription.TheOIEdescribesBSEsuspectsascattleover30months:
• affectedbyillnessesthatarerefractorytotreatment;• displayingprogressivebehaviouralchangessuchasexcitability,persistentkicking
whenmilked,changesinherdhierarchicalstatus,hesitationatdoors,gatesandbarriers;or
• displayingprogressiveneurologicalsignswithoutsignsofinfectiousillness.OftenfarmersandveterinariansknowaboutBSEonlyfrompicturesofextreme,late
stage clinical disease as portrayed by the media. They must be informed that theseextremeBSEsignsareoftennotseenandsignsareusuallyverysubtle. Itshouldberecognizedthatcattlemaydisplayonlysomeofthepossiblesigns,andthatsignsmayvary in severity. Since BSE causes no pathognomonic clinical signs, some individualanimalswithsignscompatiblewithBSEwillbeseeninallcountrieswithcattlepopula-tions.SuchanimalsshouldalwaysbeinvestigatedasBSEsuspectanimals.
Diseaseawareness:Allindividualshandlingcattle(farmers,veterinarians,personnelattheslaughterhouseandothers)mustbeabletorecognizeclinicalsignsofthedisease.Thisrequiresextensive,long-terminformationcampaignsandeducationprogrammestoimprovediseaseawareness,targetedtoeverylevelandeverysector.
Whendesigningadiseaseawarenessprogrammeforimprovingpassivesurveillance,thefollowingconsiderationsshouldbetakenintoaccount
• Messagetobeconveyed• Mediatobeused• Groupstobetargeted• Culturalaspects• Motivationfactors• Formatused
Developingeducationprogrammes isespeciallydifficult incountrieswithBSEriskbutnocases,asadministrationsandindividualsfirstmustbewillingtoconsiderthatthediseasemightbepresent.
Willingnesstoreport:Theremustbeminimalnegativeconsequencestotheidentifica-tionofapositivecaseatthefarmlevel.Themotivationofafarmertonotifyasuspectcaseiftheirwholeherd,i.e.“life-work”,couldbedestroyedwithoutreasonablejustifica-tionisminimal.Therefore,possibleconsequencesshouldbeunderstoodandacceptedas“reasonable”bythefarmers.
Compensationscheme:Thevalueofculledanimalsmustbereasonablycompensated.InmanycountriesananimalconfirmedtohaveBSEiscompensated,butnotanegativesuspectanimal.Becausemostanimalsnotifiedwillprobablybenegative,itiscrucialtoalsocompensatefarmersforthenegativesuspects.
Diagnosticcapacity:Theremustbeadequatelaboratorycompetencetoensureappro-priate handling and examination of brain tissue collected within the framework of asurveillancesystem.Theappropriatepeopleshouldbetrainedbyexperiencedlaborato-
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ries,andtheyshouldbeuptodatewithallsampling,handling,shippinganddiagnosticmethodsused.
Becauseallthefactorsdescribedabovevarygreatly,bothamongcountriesandwithincountries over time, the results of passive BSE surveillance systems are subjectiveandevaluationandcomparisonof reportedcasenumbersshouldbemadecarefully.ExperienceclearlyshowsthatmandatoryreportingofclinicallysuspectcasesaloneisnotsufficienttoderiveatruepictureoftheBSEsituation inacountry,becausesuchreportingistoodependentonthesesubjectivefactors.
2. ACTIvE SURvEILLANCETooptimize identificationofpositiveanimalsand improve thesurveillancedata, thosepopulationsofcattlethatareatincreasedriskofhavingBSEcanandshouldbeactivelytargetedwithinanationalsurveillancesystem.Cattlewithsignsofdiseasenon-specifictoBSEandcattlethatdiedorwerekilledforunknownreasonsmaybedefineddifferentlyindifferentcountries(e.g.sickslaughter,emergencyslaughter,killedcattle,fallenstock,downercows;Table1).TheprobabilityofdetectingBSE-infectedcattleishigherinthispopulation,asitmayhavebeenBSEthatledtothedebilitation,death,cullorslaugh-teroftheseanimals(SSC,2001).ManyofthesecattlemayhaveexhibitedsomeoftheclinicalsignscompatiblewithBSE,whichwerenotrecognized.Theexperienceofmanycountriesinthelastyearshasshownthat,afterclinicalsuspects,thisisthesecondmostappropriatepopulationtotargetinordertodetectBSE.
Theageofthepopulationtestedisalsoimportant,astheepidemiologicaldatashowthat cattle younger than 30 months rarely test positive for BSE. Therefore, targetedsurveillanceinmostcountriesaimstosamplecattleover30monthsofageselectivelyin the risk populations, which may be identified on the farm, at transport or at theslaughterhouse.TestingoftheseriskpopulationsisnowmandatoryinmostEuropeancountries.
Ideally,BSEsuspectcattleshouldbeseparatelyidentifiedandreported,andnotleavethepopulationthroughotherpossibleexitroutes(suchasburial).Inpractice,however,thesesuspectcasesareoftennot identifiedandareconsidered (in thebestcase)asfallenstock,andsometimesasemergencyslaughtercattle.Intheworstcase,theygointo the regular slaughter chain. This is not totally avoidable, but with good diseaseawarenessandagoodantemorteminspectionattheslaughterhouse,mostcasescanbeexcludedfromtheslaughterchain.
TABLE 1. populations of cattle to consider when planning a national BSE surveillance system.
population of cattle Category
Healthycattle Regularslaughter
Cattlewithnon-specificsigns Sickslaughter(e.g.weightloss,lossofproduction) EmergencyslaughterCattlethatdied/wereculledforunknownreasons Fallenstock(e.g.onthefarm,duringtransport) Downercows
CattlewithspecificsignsofBSE BSEsuspects
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However,despite the fact that correctly implementedsamplingof riskpopulationsandBSEsuspectswouldhypotheticallybesufficienttomeetthegoalsofBSEsurveil-lance,testingasubsampleofcattleatregularslaughtershouldbeconsideredinordertominimizediversionofquestionableanimalstoslaughter,i.e.toimprovecompliance.Iffarmersareawarethatrandomsamplingisoccurringintheslaughterhouse,andiftheprobabilityofbeingtestedislargeenough,theyarelesslikelytotrytosendsuspectanimalsdirectlytoslaughter.
Targetedsurveillancesystemsarebotheffectiveandefficient.Aftertheygainedmorewidespreadusein2001,manycountriesinEuropeandalsothefirstcountriesoutsideEuropedetectedtheirfirstBSEcases.FromtheexperiencesgainedinEurope,itisalsoclearthat it ismostcosteffectivetopromotetheeffective implementationofpassiveandtargetedsurveillanceinriskpopulationsratherthantofocusontestingoftheentireregularslaughterpopulation(Table2).
3. SURvEILLANCE SySTEmS IN DIFFERENT COUNTRIESBSE surveillance and testing programme approaches vary among countries. Somecountrieshavenosysteminplace,sometestonlyafewanimals,sometestcertainsub-populationsbutnotothers,sometestaccordingtoOIEguidelines,andsometestmanymoreanimalsthantheOIErequirements(butinsomecasesfrominappropriatepopula-tionsoragegroups).Therefore,conclusionsregardingtheextentoftheBSEprobleminacountrycannotbemadebysimplyexaminingthenumberofreportedcases,andcomparisonscannotbemadebetweencountrieswithoutconsidering implementationofthesurveillancesysteminplace.
Moreintensive,targetedsurveillanceincreasestheprobabilityoffindinganydiseasein any country (Calavas et al., 2001; Doherr et al., 2001). Therefore, when examiningacountry’sreportedBSEtestsandreportedBSEcases,thefollowingissuesmustbeconsidered
• Complianceandcapacity(i.e.inidentifyingsuspects,incollectingsamples).Thelegislationinplace,theinfrastructureavailableandtheabilitytoidentifyanddiag-nosecasesvarysubstantiallyamongcountries.
• Theproportionofthetotalcattlepopulationthatistested(orispositive).Becauseactualnumbersdonotprovideanadequaterelativepicture,theproportiontested(orpositive)mustbegiven.
• Theageof thepopulationsampled.Animalsunder30monthsofagearemuchlesslikelytotestpositive,soincludingthemintestingsystemsartificiallyraisestheproportionofnegativetests.
TABLE 2. Efficiency of testing risk and the regular slaughter populations in the European Union
Regular slaughter cattle Risk cattle
year 2003 2004 2003 2004
Numberofcattletested 8716481 9551469 1295770 1478650
NumberofBSEpositivecattle 265 166 783 520
Rateofpositives:numbertested 32892 57539 1655 2844
CosttofindonepositiveBSEcase(using€70/sample) €2.3million €4million €115841 €199094
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• Thetotalnumberofclinicalsuspectssampled.Thisreflectsthediseaseaware-nessandwillingnesstoreportinthecountry.
• The subpopulations sampled. Regular slaughter cattle have a much lower riskthanthe“riskpopulations”describedabove.
TheexamplesofSwitzerlandandtheEUarepresentedbelow.
3.1. SwitzerlandAfterimplementationoftargetedsamplinginSwitzerlandin1999(Doherretal.,1999;Doherretal.,2001),thenumberofidentifiedcasesincreased(Figure1).ThetargetedsurveillanceprogrammeinSwitzerlandcurrentlyincludes:
• passivesurveillance(clinicalsuspects);• alldiedorkilledonfarmorduringtransport,butnotcattleover30monthsofage
slaughteredforhumanconsumption(fallenstock);• allemergencyslaughtercattleover30monthsofage;• randomsampleofregularslaughtercattleover30monthsofage.
3.2. European UnionThe number of identified cases also increased in the original 15 EU member states(EU15)afterimplementationoftargetedsamplingin2001(EC,2002).IntheEU,theoffi-cialtargetedsamplingsystemisthesameforall25currentMembers.Thesurveillancesystemincludestestingallcattle:
• ofanyageandshowingclinicalsignsconsistentwithBSE;• over24monthsofageandsubjecttoemergencyslaughter(accidentorserious
physiologicalandfunctionalproblems);• over 24 months of age and died or killed on farm or during transport, but not
slaughteredforhumanconsumption(fallenstock);
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• over24monthsofageandfoundatantemorteminspectiontobesuspectedorsufferingfromadiseaseoradisorder;
• over30monthsofageandsubjecttoregularslaughterforhumanconsumption(onlySwedenisallowedtotakearandomsample).
ThenumbersoftestedandpositivecattleineachcategoryineachEUMemberStateare published and updated regularly. Although the number of cases in the EU wasincreasing in2001and2002,since2003thenumberofcases in theEUaltogether isdecreasing(EC,2003;2004).Atotalofover10millioncattleweretested intheEUin2004.Ofthese,686cattlewerepositive.SpainandPortugalweretheonlycountriesintheEU15MemberStateswithanincreaseofcasesin2003,andGermanyin2004.
However,asdescribedabove,thesenumbersmustbeexaminedinthecontextofthequalityof thesurveillanceprogrammeimplemented ineachMemberState.AlthoughallEUMembershavethesamelegalrequirementsforsurveillance(excepttheUKandSweden,whichhavespecialregulations),thenumberstestedareverydifferent.SomeofthecountriesreportingveryfewBSEcaseshavealsoperformedfewerexaminations.Theriskpopulationtestedin2004rangedbetween0.81and4.78%,andthepopulationofregularslaughtercattlebetween7%and38.2%(excepttheUKandSweden)ofthelive adult cattle population. Also, the number of suspects tested varied enormouslyamongcountries.Althoughsomevariationsinthenumberoftestsperformedcouldbeexplainedbydifferentproductionsystems,thedeviationissosignificantthatitcanonlybeexplainedbyvariableimplementationofthesurveillance.
HismeansthenumbersmaynotbereliableinsomecountriesoftheEU(andothercountries worldwide), even those with few cases. The reported numbers from somecountriesmayoverrepresenttheoverallnumberstested(andthereforeunderrepresentthenumberofpositives),becausemanycattleyoungerthan30months–evenyoungerthan24months–aretestedandthereportednumbersarethennotadjustedforage.Therefore,country-to-countrycomparisonsneedtobetreatedcautiously.Thissituationalsoemphasizesthatlegalrequirementsalonearenotsufficient,andthesurveillancesystemmustalsobeeffectivelyimplementedandcontrolled.
4. pLANNING A SURvEILLANCE SySTEm FOR BSEIfacountrydecidestoinitiateasurveillanceprogrammeforBSE,enoughtimeforprep-arationmustbeallowedandsufficientfundsallocated.First,ascientificnationalBSEriskassessmentmustbecompleted.For this, countriesmustevaluatewhatspecificinformation theyhave,what theyneed,andwhere toobtain it (see the“Riskassess-ment” chapter in this course manual). Then they must decide what infrastructure isrequired(andwhatisavailableinthecountry)toimplementthesystemeffectively.
Formanyyears,theOIEhasrecommendedthatthelevelofBSEsurveillanceshouldbe commensurate with the risk. However, prior to 2005, guidelines for the numbersof samples to test had been given only for passive surveillance. Since 2005, detailedguidelinesforcountrieswithnegligibleandhigherBSEriskareavailable(OIE2005b),suchthat:
• Whentheriskassessmentdemonstratesnon-negligiblerisk,thecountryshouldconductsurveillancethatwillallowthedetectionofBSEaroundaprevalenceofatleastonecaseper100000animalsintheadultcattlepopulation(i.e.ahigherlevelofsurveillance).
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• Whentheriskassessmentdemonstratesnegligiblerisk,thecountryshouldcon-ductsurveillancethatwillallowthedetectionofBSEaroundaprevalenceofatleastonecaseper50000animalsintheadultcattlepopulation(i.e.alowerlevelofsurveillance).
Theguidelinesassignavaluetoeverytestbasedontheriskpopulationandageoftheanimalsampled,i.e.thelowestvalueisgivenfornormalslaughteredcattleofanagebelowtwoorabovenineyears;thehighestvalueisgivenforclinicalsuspectsbetweenfourandsevenyears.Thevaluesofallthesamplestestedarethenadded.Dependingonriskandcattlepopulationsize,aspecificnumberofpointsmusttobereachedwithinsevenyears.
�. REFERENCESCalavas D, Ducrot C, Baron T, morignat E, vinard JL, Biacabe AG, madec Jy, Bencsik A, Debeer
S, Eliazsewicz m. 2001. Prevalence of BSE in western France by screening cattle at risk:
preliminaryresultsofapilotstudy.VetRec149(2),55-56
Doherr mG, Oesch B, moser m, vandevelde m, Heim D. 1999. Targeted surveillance for bovine
spongiformencephalopathy(BSE).VetRec145,672
Doherr mG, Heim D, Fatzer R, Cohen CH, vandevelde m, Zurbriggen A.2001.Targetedscreening
of high-risk cattle populations for BSE to augment mandatory reporting of clinical suspects.
PrevVetMed51(1-2),3-16
EC (European Commission).2002.Reportonthemonitoringandtestingofbovineanimalsforthe
presenceofbovinespongiformencephalopathy(BSE)in2001.http://europa.eu.int/comm/food/
food/biosafety/bse/bse45_en.pdf
EC. 2003.Reporton themonitoringand testingof ruminants for thepresenceof transmissible
spongiform encephalopathy (TSE) in 2002. http://europa.eu.int/comm/food/food/biosafety/bse/
annual_report_2002_en.pdf
EC. 2004.Reporton themonitoringand testingof ruminants for thepresenceof transmissible
spongiformencephalopathy(TSE)intheEUin2003,includingtheresultsofthesurveyofprion
proteingenotypesinsheepbreeds.http://europa.eu.int/comm/food/food/biosafety/bse/annual_
report_tse2003_en.pdf
Heim D, mumford E.2005.ThefutureofBSEfromtheglobalperspective.MeatScience70,555-562
Heim D, wilesmith Jw.2000.SurveillanceofBSE.ArchVirolSuppl16,127-133
SSC (Scientific Steering Committee of the European Commission).2001.Opinionrequirementsfor
statistically authoritative BSE/TSE surveys. http://europa.eu.int/comm/food/fs/sc/ssc/out238_
en.pdf
OIE (world Organisation for Animal Health).2005a.Bovinespongiformencephalopathy.TerrestrialAnimalHealthCodeChapter2.3.13http://www.oie.int/eng/normes/MCode/en_chapitre_2.3.13.
htm
OIE. 2005b, Surveillance for bovine spongiform encephalopathy. Terrestrial Animal Health CodeAppendix3.8.4.http://www.oie.int/eng/normes/MCode/en_chapitre_3.8.4.htm
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Risk assessmentRISk ASSESSmENT
1. BASIC CONCEpTS OF RISk ANALySIS AND ImpORT RISkRiskhastwocomponents:
• thelikelihoodofaneventoccurring(e.g.adiseaseoutbreak);• thelikelymagnitudeoftheconsequences(e.g.scaleofanoutbreak,costsofcon-
trol/eradication,tradelosses);Riskanalysisisastructuredprocessdesignedtodetermine:• whatcangowrong;• howlikelyitistogowrong;• howseriousitwouldbeifitwentwrong;• whatcanbedonetoreducethelikelihoodand/orseriousnessofitgoingwrong.
Riskanalysis isa tool thatusesdata, informationandopinions fromvariousdisci-plinessuchasepidemiology,pathology,microbiology,virologyandeconomics.Itblendsinductiveanddeductivereasoningand judgement,and itmustbeableto incorporateincomplete information. It can be qualitative or quantitative, and can address a widevarietyofquestions,bothgenerallyandspecifically.
Allriskanalyses,bydefinition,aremadeupoffourcomponents:hazardidentification,riskassessment,riskmanagementandriskcommunication.Thesecomponentswillbedescribedindetailinsection1.4ofthischapter.
Becausetransmissiblespongiformencephalopathies(TSEs)canbespreadthroughmovementofanimalsandanimalproducts,riskanalysiscanbeusedtoevaluatetherisksinvolvedininternationaltrade.Thisbecomesimportantin:
• identifyingandexaminingtherisksoftransferringtheTSEagentbetweencoun-tries;
• developingconditionsthatallowtradetoproceed“safely”.• fulfillingdomesticresponsibilities(e.g.biosecurityandquarantinelegislation);• fulfillinginternationalresponsibilities(e.g.theSanitaryandPhytosanitaryAgree-
ment of the World Trade Organization (WTO) and code standards of the WorldOrganisationforAnimalHealth(OIE);detailedinsection1.4ofthischapter)
Riskanalysescanalsobeusedbycountriesinitiallytoassesstheirownnationalriskof having a TSE. In addition, the assessments can be used to develop, compare andevaluate domestic strategies for control, eradication, surveillance and monitoring ofTSEs.
ResultscanbeusedtoguideTSE-relatedpolicydecisionsthroughassessmentofthesignificanceofrisks.Policymakersmustconsidermanyfactors,includingtheassump-tionsmadeintheanalysisandtheperceptionoftherisks,andthenevaluatewhatriskwillbeconsideredacceptableandwhatpoliciestoimplement.
Theprinciplesofriskanalysisaredescribedgenerallyinthissectiononimportriskanalysis.Insections2and3ofthischapter,theconceptswillbeappliedtoassessmentofBSErisk.
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1.1. International trade conceptsTheWTOSanitaryandPhytosanitary(SPS)Agreementdefinestheconceptoffreetradeinanimalandanimalproducts.Itspecifiesthat,forWTOmembercountries,nosanitarymeasures (i.e. trade restrictions) shouldbe inplaceunless there isa likelihood thata disease may enter and lead to unacceptable biological or economic consequences(WTO,1994).
According to the SPS Agreement sanitary measures are implemented to protecthumanand/oranimalhealthfromtherisksarisingfromdiseasesentering,establish-ingorspreading.Theymayincludetesting,inspectionand/orcertificationprogrammes,andmustonlybeappliedtotheextentnecessarytoprotecthumanoranimalhealth.Theymaynotbeappliedarbitrarily,maynotallowtradediscriminationamongcountrieswheresimilardiseaseconditionsexist,andmaynotbeusedtodisguisetraderestric-tions.Althoughthemeasuresofcountriesmaydiffer,theymaybeacceptedasequiva-lentiftheyachievethesameobjective.
BecauseWTOrecognizestheOIEastherelevantinternationalorganizationrespon-sible fordeveloping international standardsonanimalhealthand zoonoses, sanitarymeasuresshouldbebasedonOIEstandardswhentheyexist.AnymeasuresexceedingOIEstandards,however,mustbesupportedbyariskassessment.
Ifscientificevidenceisinsufficienttoconductsuchariskassessment(e.g.foranewlyemerging disease), countries may adopt interim measures, which are based on theamountof informationavailable.However,additional informationneeds tobesoughtandassessedinareasonableamountoftime.
1.2. principles of import risk analysisImportriskanalysesareusedtoevaluatediseaserisksobjectivelyandtransparently,sothatspreadofhumanandanimaldiseaseagentscanbeavoidedandimportrestrictions(sanitarymeasures)canbejustified.ThebasicSPSriskassessmentprocessincludesthefollowingsteps:
• identifydiseasestobeprevented fromentering,establishing,orspreading,andtheirassociatedpotentialbiologicalandeconomicconsequences;
• evaluatethelikelihoodofdiseaseentry,establishmentorspread,andtheassoci-atedpotentialbiologicalandeconomicconsequences;
• evaluatethelikelihoodofdiseaseentry,establishmentorspreadaccordingtothemeasuresthatmightbeapplied.
Theanalysisshould:• bebasedontheOIEframework(Figure1)(OIE,2005a,b);• fulfiltheobligationsoftheSPSAgreement;• bebasedonthebestavailablescientificinformation;• onlyconsiderdisease-associatedeffects;• only evaluate the likelihood of disease entry, establishment or spread and its
potentialconsequences,notthepossibilityoftheseevents;• evaluatetherisksaccordingtothemeasuresthatmightbeapplied;• betransparent.
Toconductariskanalysiscomprehensively,ateamisgenerallyrequired.Theteamshould be made up of individuals skilled in epidemiology, critical thinking, domesticquarantine law, the SPS Agreement, statistics, probability modelling and economics.Thislikelyincludesepidemiologists(animalandhuman),governmentregulators,stat-
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isticians,mathematicalmodellers,economists,etc.Althoughalltheseindividualsmaynotbeavailableinmanysmallercountries,thereareoftenopportunitiesforcollabora-tionamongcountrieswithcommonconcernsandrisks.
An important concept in the risk analysis process is transparency. Transparencymeans comprehensive documentation of data, information, assumptions and uncer-tainties, methods, results, discussion and conclusions, and should be supported bya reasoned and logical discussion. All conclusions should be fully referenced. Theserequirementshelptoensure:
• fairnessandrationality;• consistencyindecisionmaking;• easeofunderstandingbyalltheinterestedparties;• thatassumptionsaredocumented;• thatuncertaintiesaredealtwithappropriately;• thatreasonsforconclusionsandrecommendationsareobvious;• thatinterestedpartiesareprovidedwithclearreasonsfortheimpositionofsani-
tarymeasuresorrefusaltoimport.Ariskanalysis inevitably includesadegreeofsubjectivityduetopersonalopinions
andperceptionsofanalysts,expertsanddecisionmakers.Onewaytopromoteobjectiv-ityistoensuretransparency.Anotherwayistohavetheanalysisundergoapeerreview.Itmustberecognized,however,thatthepeerreviewprocessrequiresasignificanttimecommitment.Aswell,reviewersshouldbechosenstrictlyonthebasisoftheirstatusasacknowledgedauthoritiesintheirfield,andgivenspecifictermsofreferenceforthereview.
Finally, it is important to remember that even the best and most complete riskanalysis does not provide definitive answers, but only provides information for thoseindividuals who must then make decisions (e.g. quarantine officers, chief veterinaryofficers,politicians).Theinformationoftenstronglysuggestscertainrecommendations.However,decisionsmustoftenalsoconsiderotherfactors.
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1.3. Defining the scope of the risk analysisThefirststepinanyriskanalysisisspecificallydefiningthescopeintermsofthefol-lowingvariables:
• Commodity:aparticularcommodity(e.g.beefmeat)oracategoryofcommodities(e.g.liveviralvaccines)
• Animal: a single animal species (e.g. cattle) or a group of similar species (e.g.ruminants)
• Disease:aparticulardisease(e.g.BSE)oragroupofdiseaseswithsimilarepide-miologicalcharacteristics(e.g.TSEs)
• Exportingcountry:asinglecountry/bilateral (e.g.USA)oragroupofcountries/multilateral(e.g.EuropeanUnion)oranycountry(generic)
Scientificnamesshouldbeusedtodescribeanimalspeciesanddiseaseagents,e.g.domestic cow = Bovis bovis, porcine reproductive and respiratory syndrome (PRRS)virus=OrderNidoviralesFamilyAteriviridaeGenusAterivirus.
Thenature,sourceandintendeduseofthecommoditymustbefullydescribed(e.g.“chilledorfrozenbonelessbeefmeatfromtheUKforhumanconsumption”).Also,therelevantmethodsofproduction,manufacturing,processingortestingthatarenormallyapplied (e.g.chilling, freezing,cooking,curing, irradiating)andanyqualityassuranceprogrammesthatmayapply(e.g.HACCPprogrammesfortheproductionofbeefmeat)andhowtheyareverifiedshouldbedescribed.Thelikelyannualvolumeoftrademaynotbereadilyavailable,butshouldbeatleastestimated.
Finally, thepurposemustbeclearlystated,e.g. “toassess the likelihoodofPRRSvirusspreadingorbecomingestablishedinNewZealandanditslikelyconsequencesasaresultofimportingchilledorfrozenpigmeatforhumanconsumptionfromtheUSA”.Itshouldalsobestatedifrecommendationsaretobeincluded.
1.4. OIE risk analysis frameworkBecauseimportriskanalysesshouldbebasedontheOIEframework(Figure1) (OIE,2005a,b),theymustthereforeincludetheaspectsofriskcommunication,hazardiden-tification,riskassessmentandriskmanagement,asdescribedbelow(Figure2).
Risk communicationRiskcommunicationistheprocessbywhichinformationandopinionsregardinghaz-ardsandrisksaregatheredfrompotentiallyaffectedandinterestedparties(thestake-holders)duringa riskanalysis,andbywhich theresultsof the riskassessmentandproposedriskmanagementmeasuresarecommunicatedtothedecisionmakersandallotherinterestedpartiesinboththeimportingandexportingcountries.Riskcommu-nicationshouldbeopen,interactive,iterative,transparentandtimely,andbetargetedtotheaudiencethatwillbereceivingtheinformation.Effectiveriskcommunicationwillleadtoabetterunderstandingoftherationaleforaparticulardecisionevenifalldiffer-encesandconflictsamongstakeholdersarenotresolved.
Ariskcommunicationstrategytoidentifyinterestedpartiesanddeterminethemostappropriatemeansofcommunicatingwiththemshouldbeestablishedatthebeginningofeachriskanalysis.Communicationshouldcontinuethroughouttheanalysis.
Riskcommunicatorsdescribean importantcomponentof risk, termed“outrage”,whichaffectsdifferencesinperceptionofrisk(Sandman,2006).Thepublicestimatesariskashighwhenoutrageishigheventhoughtheactualhazardmaybelow(whereas
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riskassessors,ignoringoutrage,presenttheriskaslowwhenthehazardisestimatedtobelow).“Outrage” isaffectedbytheperceptionofrisks, forexampleasbeingvol-untaryvscoerced,fairlyvsunfairlydistributed,naturalvsartificial,non-memorablevsmemorable, chronic vs catastrophic, knowable vs unknowable, individually controlledvscontrolledbyothers,morally irrelevantvsmorallyrelevant,andgivenlessvsmoremediaattention.
FigurE 2
Flowchart of the import risk analysis process
Project initiatione.g. market access request from a potential importer or trading partner
Establish a Project TeamEstablish the risk analysis scope and risk communication strategy
Hazard identification
Risk analysis
Peer review of a draft risk analysis
Publish the risk analysis for stakeholder consultation
Announce the final decision
Draft an Import Health Standard
Stakeholder consultation including WTO notification
Import Health Standard approved
Publish a review of stakeholder submissions and recommended
modifications
Com
munication w
ith interested parties
Source:adaptedfromMurray(2001)
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Hazard identificationPotentialhazardsmustbeclearlyidentifiedbeforetheycanbeassessedormanaged.Hazard identification isusedfirst to identifypathogensthatcouldpotentiallyproduceadversebiological,environmentaloreconomicconsequences.
Asafirststep,acomprehensivelistofallthepathogensassociatedwiththeimportedanimalorcommodityshouldbemade,startingwiththediseasesnotifiabletotheOIE(OIE,2005c)andincludingothersasappropriate.
Inordertobeclassifiedasahazardandbesubjecttofurtherconsiderationinariskassessment,thesepathogensmustmeetspecificcriteria.First,thepathogensmustbeknowntoaffecttheanimalsbeingimported.Forimportedcommodities,thepathogenmustaffecttheanimalsfromwhichthecommodityisderivedandthecommoditymustbeapotentialvehicleforthepathogen.
It must be determined whether the pathogen is likely to be present in the export-ingcountry.Forthis,therelevantzoning/regionalizationparameters,surveillanceandmonitoringsystems,andveterinaryservicesintheexportingcountrymustbeevaluated.Thepathogenmustalsobeconsideredexotictotheimportingcountryorregion.Finally,thepathogenmusteitherbeunderofficialcontrolintheimportingcountryorbeshowntobelessvirulentthanstrainspresentintheexportingcountry.
Sources of information about the pathogens and the countries include the OIE,ProMED(ProMEDMail,2006),directliaisonwiththeveterinaryserviceinaparticularcountry,veterinaryliteratureoranimalhealthstatusinformationpublishedbyindividualcountries.
Ariskanalysismaynotberequiredeitherifhazardsarenotidentified(i.e.thepatho-gensdonotmeettheabovecriteria,inwhichcasesrestrictionsarenotjustified)orifmeasuresrecommendedintheOIECode(OIE,2005d)areappliedtoeachhazard.
Risk assessment Risk assessment evaluates the likelihood of entry, establishment or spread of apotentialhazardaswellasitspotentialbiological,environmentalandeconomicconse-quences.Assessmentsshouldbebasedonthebestavailablescientificinformation,betransparentandbereviewedasnewinformationbecomesavailable(e.g.asthevolumeoftradeincreases,ifthediseasestatusofatradingpartnerchanges).
Riskcanbeevaluatedbyeitherqualitativeandquantitativemethods,orboth.Qualita-tiveriskassessmentisareasonedandlogicaldiscussionwherelikelihoodisexpressedinsubjectiveterms(e.g.high,medium,low,negligible).Aqualitativeassessmentisthemostcommontypeofriskassessment,particularlyforroutinedecisionmaking,andisappropriate inmostsituations.Aquantitativeriskassessmentshouldalwaysbepre-cededbyaqualitativeassessment.
Quantitative riskassessment requirescomputers,dataspreadsheets, riskanalysissoftware,andmathematicalmodellingskillsandtraining.Itinvolvesdevelopingamath-ematicalmodeltolinkvariousaspectsoftheepidemiologyofadisease,whereboththeinputsandoutputs(results)areexpressednumerically.Quantitativeassessmentsmaybeusefuladjunctstoqualitativeassessmentsinordertogainfurtherinsights,identifycriticalsteps,assesstheimpactofuncertaintyandcomparemanagementstrategies.However,itisveryimportanttorecognizethatalthoughquantitativeassessmentsgen-erateanumericalresult,thisdoesnotmeanaquantitativeassessmentismoreobjec-tiveor that theresultsaremoreprecise. Insomecases,dataare lackingandexpert
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Risk assessmentopinionmustbeincorporated,addingsubjectivity.However,aquantitativeassessmentmayallowexpertopiniontobemodelledtransparently.
Both qualitative and quantitative risk assessments inevitably include a degree ofsubjectivity.Twosourcesofsubjectivityare thepersonalperceptionsof riskanalysts,expertsanddecisionmakersandtheselectionofanappropriatemodelstructure(e.g.whichpathwaystoincludeorexcludeandthetypeofdistributionschosentorepresentavariable).Transparencyandpeerreviewhelptoensureareasonablelevelofobjectivity.
Semi-quantitative methods are not necessarily more objective than strictly quali-tative techniques because the quantitative aspects are not as critically applied andtheremaybeaconsiderable lackof transparency. Insemi-quantitativeassessments,numbersmaybearbitrarilyappliedtoqualitativeestimatesandthenmaybearbitrarilycombined,oftengivingamisleading impressionofobjectivityandperhaps leading toinconsistentoutcomes.Semi-quantitativemethodsmaybeusefultoprioritizerisksinanon-contentiousenvironment;however,theyoffernoadvantagesoverawellresearched,transparentandpeerreviewedqualitativeassessment.
Uncertaintyandvariability(thissectionexcerptedfromMurray,2001)Thewayuncer-taintyhasbeendescribedbyriskanalystsfromvariousdisciplineshasledtoadegreeofconfusion.Riskanalysisisessentiallyatoolaimedatpredictingthefuture.Forexample,wemightwanttopredicttheweightofaweanerpigchosenatrandom.Weknowfromourownobservationsthatthereisagreatdealofnaturalvariationbetweenindividualpigsofthisage.Suchvariabilityisabiologicalreality.Whilewemighthaveagood“feel”fortherangeandwhatanaveragemightbe,itisonlybyweighingseveralpigsthatwecanbegintomakesomeaccuratepredictions.Asmoredataarecollected,moreknowl-edgeisacquired,andwecandescribethevariationintheweightsofweanerpigswithincreasingcertainty,enablingustobe increasinglyconfidentofourpredictions. Ifweweighedallpigsinthepopulationwewouldhaveaperfectunderstandingoftheaverageweightandhowmuchvariationexistsandtherewouldbenouncertainty.Obviously,thisisimpracticalandweneedtoachieveabalancebetweenacquiringperfectknowledgeand obtaining reasonable estimates upon which we can base our predictions with areasonablelevelofconfidence.Uncertainty, then,maybethoughtofasameasureofthe incompletenessofone’sknowledgeor informationaboutanunknownquantity. Itisimportanttorememberthatevenwithcompleteknowledge(thatis,nouncertainty)variabilitystillexists.
Theseideascanbeextendedtoimportriskanalysiswhere,forexample,wewanttopredictthelikelihoodofanoutbreakoffoot-and-mouthdisease(FMD) in“CountryA”followingtheimportationofgoatcheesefrom“CountryB”.Foranoutbreaktooccur,acomplexchainofeventsneedstotakeplacebeginningwith:
i) anoutbreakofFMDin“CountryB”thatresultsinatleastoneinfectedgoatshed-dingFMDvirusinitsmilk;
ii) thevirussurvivingpasteurization,thecheesemanufacturingprocess,storageandtransportationto“CountryA”;
iii)asusceptibleanimalingestingdiscardedcheesein“CountryA”,becominginfect-edandtransmittingthevirustootheranimals
TheremaybesomeverygoodinformationonthesurvivalofFMDvirusinpasteurizedmilk,somelimitedinformationontheoccurrenceofFMDin“CountryB”andvirtuallynoinformationonthelikelihoodofsusceptibleanimalsingestingcheesescrapsin“Coun-tryA”.Apredictioninthesecircumstanceswillbebasedoninformationrangingfrom
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poortoexcellent.Asaresult,wecouldconcludethatthereissignificantuncertaintyintheestimatesfortheoccurrenceofFMDin“CountryB”andtheexposureofsusceptibleanimalsin“CountryA”.Theimpactoftheseuncertaintiesontheoverallestimateofriskneedstobecarefullyconsidered.Forinstance,theimpactislikelytobeinsignificantifpasteurizationispredictedtokillFMDviruseffectively.Ontheotherhand,ifpasteuri-zationcannotberelieduponbecausetheFMDvirusiseitherheattolerantorthereissignificant variability in its effectiveness, the impact of these uncertainties becomesmuchmoreimportant.
Wherethereissignificantuncertaintyintheestimatedrisk,aprecautionaryapproachtomanagingriskmaybeadopted.However,themeasuresselectedmustneverthelessbebasedonariskassessmentthattakesaccountoftheavailablescientific informa-tion. In thesecircumstances themeasuresshouldbereviewedassoonasadditionalinformationbecomesavailableandbeconsistentwithothermeasureswhereequivalentuncertaintiesexist.Itisnotacceptabletoconcludesimplythat,becausethereissignifi-cantuncertainty,measureswillbebasedonaprecautionaryapproach.Therationaleforselectingmeasuresmustbemadeapparent.
ScenariotreesDevelopmentofscenariotreescanassistinidentifyinganddescribingbiologicalpathways,whichhelptoensurealogicalchainofeventsisassessed,aswellastofacilitateeffectiveriskcommunication.Theyassistinidentifyingdatarequiredandincommunicatingthemodelstructure.Scenariotreesareanessentialcomponentofquantitativeriskanalyses.
To develop a scenario tree (Figure 3), first the initiating event and the end point(outcomeofinterest)mustbedefined.Thestepsinthemiddlearethenidentified,andlikelihoodstatementsareassignedtoeachstep.
ComponentsofariskassessmentAriskassessmenthasfourcomponents:releaseassessment, exposure assessment, consequence assessment and risk estimation(Figure4).
Areleaseassessmentdescribesthebiologicalpathway(s)necessaryforacommoditytobecomeinfectedorcontaminatedintheexportingcountry,andestimatesthelikeli-hoodofthecommodityalreadybeinginfectedorcontaminatedwhenimported.Itcon-sidersbiological,countryandcommodityfactors.Ariskassessmentmaybeconcludediftheresultsofthereleaseassessmentshowthelikelihoodofintroducingthehazardisnegligible.
Anexposureassessmentdescribesthebiologicalpathway(s)necessaryforanimalsandhumanstobeexposedtothehazardintheimportingcountry,andestimatesthelikelihoodoftheseexposure(s)occurring.Asinthereleaseassessment,theexposureassessmentconsidersbiological,countryandcommodityfactors.Theriskassessmentmaybeconcludediftheresultsoftheexposureassessmentshowthelikelihoodofeveryexposurepathwayisnegligible.
Aconsequenceassessmentidentifieswhatmighthappen,i.e.thepotentialbiological,environmentalandeconomicconsequencesassociatedwiththehazard,andestimatesthelikelihoodoftheseconsequencesoccurring.Itconsidersdirectconsequences(suchas production and public health impacts) and indirect consequences (such as costsof control and trade losses), but should not consider non-disease associated conse-quences(suchastheimpactoftheimportedcommodityondomesticindustriesthroughincreasedcompetition).
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Risk assessment FigurE 3
Scenario tree
Initiatingevent
Step 1
Event is likely
Event is NOT likely
Event is NOT likely
Event is NOT likely
Event is likely
Event is likely
Step 2
End point(outcome of
interest)occurs
End point(outcome of
interest)does NOT occur
End point(outcome of
interest)does NOT occur
End point(outcome of
interest)does NOT occur
Source:Murray,2001.
FigurE 4
Components of a risk assessment
Infection/ contamination
NationalBorder
Exposure of susceptible
animals
ReleaseAssessment
ExposureAssessment
ConsequenceAssessment
RiskEstimation
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Aconsequenceassessmentidentifiespotential“outbreak”scenarios,e.g.thediseaseeither:
• doesnotspreadwithintheexposedpopulation;• spreadswithintheexposedpopulation,butisquicklyidentifiedanderadicated;• establishes within the exposed population and spreads to other populations
beforeeventuallybeingeradicated;• establishes within the exposed population, spreads to other populations and
becomesendemic.Then the likelihood of each “outbreak” scenario is estimated, and the likely mag-
nitude of the consequences of each “outbreak” scenario at the farm/village, district,regionalandnationallevelsisalsoestimated.Theriskassessmentmaybeconcludedifpotentialconsequencesarenotidentified,orthelikelihoodofeverypotentialconse-quenceisnegligible.
The risk estimation summarizes the results from the release, exposure and con-sequence assessments to estimate the likelihood of the hazard entering, spreadingor becoming established and leading to adverse consequences. It is not sufficient toconcludethatthereisapossibilityoftheseevents,butanevaluationofthelikelihoodofeachofthesemustbeundertaken,asgiveninthefollowingscheme:
Releaseassessment(likelihoodofentry)Is the likelihood negligible that the commodity is carrying the hazard when it isimported?
• IftheanswerisYES,theriskestimateisclassifiedasnegligible.• IftheanswerisNO,thenconductanexposureassessment.
Exposure assessment (likelihood of susceptible animals and/or humans becomingexposed)Is the likelihood negligible of susceptible animals and/or humans being exposed viaeachandeveryexposurepathway?
• IftheanswerisYES,theriskestimateisclassifiedasnegligible.• IftheanswerisNO,thenconductaconsequenceassessment.
ConsequenceassessmentIs the likelihood of each and every significant biological, environmental or economicconsequencenegligible?
• IftheanswerisYES,theriskisestimatedtobenegligible.• IftheanswerisNO,thenproceedtoriskmanagement.
Risk managementRisk management is the process of identifying, selecting and implementing sanitarymeasures tomanageeffectively the risksposedby thehazard(s)associatedwith thecommodity under consideration. It is not acceptable to simply identify the range ofmeasuresthatmightreducetherisks;theremustbeareasonedrelationshipbetweenthemeasureschosenandtheriskassessmentsothattheresultsoftheriskassess-ment support the measure(s). Measures recommended in the OIE code (OIE, 2005d)are the international standard, but where OIE recommendations do not exist or the
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Risk assessmentproposedmeasuresaremorestringentthantheOIE,measuresmustbesupportedbyariskanalysisinordertofulfilWTOSPSobligations(WTO,1994).
Risk management is comprised of four steps: risk evaluation, option evaluation,implementation,andmonitoringandreview.
Risk evaluation refers to the assessment process, and implementation of sanitarymeasurescanonlybejustifiedif theriskestimateisgreaterthannegligible. Inoptionevaluation,differentsanitarymeasuresareidentified,evaluatedandselectedtomanagetheriskseffectively.Allmeasuresconsideredmustberelatedtotheoutcomeoftheriskassessment,becausetheWTOSPSAgreementrequiresthatthelikelihoodoftheentry,establishmentorspreadofahazardmustbeevaluatedaccordingtothemeasuresthatmightbeapplied.Thefollowingguidelinesmustbeensuredwhenselectingoption(s):
• theoption(s)arebasedonscientificprinciples;• that the OIE Code’s sanitary measures are considered. If there is a scientific
justificationthatthesemeasuresdonoteffectivelymanagetherisks,measuresthatresultinahigherlevelofprotectionmaybeapplied.Alternatively,measureslessstringentthanthoserecommendedmaybeappliedwherethereissufficientjustificationthattheriskscanbeeffectivelymanagedusingthosemeasures;
• theoptionsareappliedonlytotheextentnecessarytoprotecthumanoranimallifeorhealth;
• negativetradeeffectsareminimized;• theoptionsarenotappliedarbitrarily;• the options do not result in discrimination between exporting countries where
similarconditionsexist;• theoptionsare feasiblebyconsideringthetechnical,operationalandeconomic
factorsaffectingtheirimplementation.Measuresmustthenbeeffectivelyimplemented,aswellasaudited(monitored)and
reviewedthroughinspectionsand/orrandomcheckstoensurethattheyareachievingtheintendedresults.
2. RISk ASSESSmENT FOR BSE IN COUNTRIES Formanyyears,BSEwasconsideredaproblemexclusivelyof theUK.Evenafter thedetectionofBSEcasesincountriesoutsidetheUK,theriskofhavingBSEwascategori-callydeniedbymanyothercountriesinEuropeandthroughouttheworld.
Anunfortunatepatterncanbeseeninmostcountries,relativetoBSE.MeasuresareoftenonlyimplementedafterthefirstBSEcaseisdetectedor,ifmeasuresarealreadyinplace, only thenare theyappropriately implementedandcontrolledandadditionalmeasures taken.Thisoftensignificantly improves thesituationbut itdoesnotelimi-natetheriskimmediately,ascaseswillcontinuetobereporteduntilallanimalsbornbeforethenationalsystembecamestable(i.e.abletoavoidrecyclingandamplificationoftheBSEagent)havepassedthroughtheirlifespan.Theconceptofstabilityisfurtherdescribedinsection2.3ofthischapter.
Ina jointWHO/FAO/OIETechnicalConsultationonBSE inJune2001, itwasstatedthatmaterialspotentiallyinfectedwithBSEhavebeendistributedthroughouttheworld(OIE,2001).Atthisconsultation,theOIErecommendationonBSEriskwassupportedthrough the conclusion that all countries should evaluate their potential exposurethroughasystematicassessmentofrisk.
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2.1. BSE status of countries according to the OIE (excerpted in part from OIE, 200�d)Before2005,theOIEcategorizedcountriesintothefollowingfivegroups:
BSEfreecountryorzoneBSEprovisionallyfreecountryorzoneCountryorzonewithaminimalBSEriskCountryorzonewithamoderateBSEriskCountryorzonewithahighBSErisk
InMay2005,anewBSEchapterwasadoptedreducingthenumberofcategoriestothree:Country,zoneorcompartmentwithanegligibleBSEriskCountry,zoneorcompartmentwithacontrolledBSEriskCountry,zoneorcompartmentwithanundeterminedBSErisk
InadditiontoanassessmentofBSErisk,theOIEstatuscategorizationforBSEincludesevaluationofsomeofthemeasuresinplaceinthecountry.AccordingtotheOIECode,factorsevaluatedintheestablishmentofBSEstatusshouldinclude:
• theoutcomeofariskassessmentidentifyingallpotentialfactorsforBSEoccur-renceandtheirhistoricperspective;
• ongoingawarenessprogrammesforveterinarians,farmersandworkersinvolvedin transportation, marketing and slaughter of cattle to encourage reporting ofallcattleshowingclinicalsignsconsistentwithBSEintargetsubpopulationsasdefinedintheOIECodeAppendixonBSEsurveillance(OIE,2005e,f);
• compulsorynotificationandinvestigationofallcattleshowingclinicalsignscon-sistentwithBSE;
• examinationinanapprovedlaboratoryofbrainorothertissuescollectedwithintheframeworkofthesurveillanceandmonitoringsystem.
Whentheriskassessment(whichtakesintoaccountthesurveillancereferredtointhe release and exposure assessments above) demonstrates non-negligible risk, thecountry should conduct “Type A” surveillance in accordance with the OIE Code (OIE,2005e). When the risk assessment demonstrates negligible risk, the country shouldconduct “TypeB”surveillance (see the “Surveillance forBSE”chapter in thiscoursemanual).
Forexample,thecattlepopulationofacountry,zoneorcompartmentmaybecon-sideredatnegligibleriskwhenariskassessmenthasbeenconductedandithasbeendemonstratedthatappropriategenericmeasureshavebeentakenforarelevantperiodoftimetomanageallriskidentified.
Currently,Australia,Argentina,NewZealandandUruguayareclassifiedaccordingtothepre-2005systemas“BSEfree”andChile,Iceland,ParaguayandSingaporearecategorizedas“BSEprovisionally free”.CountriesapplyingtotheOIEfordesignationaftertheendof2006willbere-assessedbasedonthe2006categorizationsystem(OIE,2005g).
Itisclearthat,accordingtotheabovedefinitions,theBSEstatusofacountry(orzoneorcompartment,asdefinedbyOIE)canonlybedeterminedonthebasisoftheoutcomeofanationalBSEriskassessment.TheOIECode lists the followingpotential factorsthatmustconsideredinsuchanassessment:
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Risk assessmentReleaseassessment:• thepresenceorabsenceofanimalTSE1agentsinthecountry;• MBMorgreavesmanufacturedfromtheindigenousruminantpopulation;• importedMBMorgreaves,liveanimals,animalfeedandfeedingredients;• importedproductsof ruminantorigin forhumanconsumption (whichmayhave
containedSRMandmayhavebeenfedtocattle)orforinvivouseincattle.Relevantsurveillanceandotherepidemiologicalinvestigationsshouldbetakeninto
accountincarryingouttheassessment.
Exposureassessment:• domesticrecyclingandamplificationof theBSEagent throughconsumptionby
cattle of MBM or greaves of ruminant origin, or other feed or feed ingredientscontaminatedwiththese;
• the use of ruminant carcasses (including from fallen stock), by-products andslaughterhousewaste,theparametersoftherenderingprocessesandthemeth-odsofanimalfeedmanufacture;
• thefeedingofruminantswithMBMandgreavesderivedfromruminants,includ-ingmeasurestopreventcrosscontaminationofanimalfeed;
• thelevelofsurveillanceforBSEconductedonthecattlepopulationtothattimeandtheresultsofthatsurveillance.
2.2. Geographical BSE risk assessment (text summarized and adapted from SSC references, 2000-2003) OnthebasisoftheriskassessmentcriteriasetbytheOIE,theScientificSteeringCom-mittee of the European Commission (SSC) has carried out a geographical BSE riskassessment(GBR)inanumberofcountries.TheGBRisaqualitativeindicatorofthelikelihoodofthepresenceofoneormorecattlebeinginfectedwithBSE,atagivenpointintime,inacountry.WherepresenceofBSEisconfirmed,theGBRgivesanindicationofthelevelofinfection.TheriskofhumanexposurewithinthecountryisnotanoutputoftheGBR,norareotherTSEsconsidered.
TheGBRisbasedonqualitativeriskassessmentmethodology,whichusesinforma-tiononriskfactorsthatcontributeeithertothepotentialforintroductionofBSEintoacountryorregionortheopportunityforrecyclingoftheBSEagentinacountryorregion.ThefollowingquestionsareansweredthroughtheGBR:
• Wastheagentintroducedintothecountrybyimportofpotentiallyinfectedcattleorfeed(MBM),andifsotowhatextent?
• Whatwouldhappeniftheagentwereintroducedintotheanimalproductionsys-tem,i.e.woulditbeamplifiedoreliminated?
Assumptions madeIn the GBR, contaminated feed is considered as the only possible route of infectionbecauseepidemiologicalresearchhasclearlyshownthattheoriginandmaintenanceoftheBSEepidemicintheUKweredirectlylinkedtotheconsumptionofinfectedMBM
1 In2006,theOIEBSEchapterwasmodifiedtoincludeonlyBSE(andnotallTSEs)inthereleaseassessment.
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bycattle.Similarly,forallcountriesotherthantheUK,theonlypossibleinitialsourceofBSEconsideredistheimportofcontaminatedfeedorinfectedanimals.Otherassump-tionsandconsiderationsinclude:
• PotentialdomesticinitialsourcesofBSE(e.g.spontaneousoccurrenceofBSEorotherTSEs in thecountry)arenotconsidered,because thesesourceshavenotbeenscientificallyconfirmedandnobasisexistsforassessingtheirriskpoten-tial.
• Thepossible impactofmaternal transmission isnotconsideredbecauseof thequalitativenatureofthemethod,therelativelylesserimportanceofthisfactorincomparisontofeed,andthelackofscientificconfirmationofitsexistence.
• Nootherrouteoftransmissionisconsidered.Whiletheexistenceofathirdmodeoftransmission(afterfeedandverticaltransmission)ofBSEhasbeenpostulatedand cannot be excluded, to date there is no scientific evidence to establish itssignificance.
• Blood, semen and embryos are not seen to be effective transmission vectors.Accordingly,bloodmealisalsonotconsideredtobearisk.
BSE risk concept of the GBRBasicknowledgeregardingtheepidemiologyandamplificationofBSEmustthereforebeknownpriortotheinitiationoftheGBR(oranyriskassessment)inacountry.Also,theriskofBSEinothercountriesbecomesimportantwhentheriskswithinthecountryareevaluated.
Asstatedabove,theGBRconsidersthattheBSEagentisintroducedintoacountryviainfectedcattleorMBM(“externalchallenge”).Theoutbreakmaythenbepropagatedduetoamplificationoftheagentthroughdomesticrecyclingoftheproducts.Figure5showstheamplificationcycleandexternalchallenges,andformsthebasicframeworkforunderstandingtheGBR.
Insomecountries,whenanimalsareslaughtered,upto50%oftheirtissuesarenoteatenbyhumansandsoentertherenderingsystem.Attherenderingplant,thesetis-suesareprocessedintomanydifferentby-products,primarilyMBM.Otherby-productsmayincludetallow,greaves,meatmealandbonemeal.
Dependingontheamountofinfectivitypresentinthetissuestoberenderedaswellastherenderingprocessingparameters,theresultantby-productsmaycontaininfec-tive BSE agent. When these tissues are fed to cattle, the disease is transmitted andthecyclestartsagain.Theabilityofthemeasuresinplacetopreventthisamplificationiscalledthestabilityoftheinternalsystem.Themorestabletheinternalsystem,thesmallerthe“internalchallenge”,andthelowertheriskofdomesticexposure.
ThisamplificationmayremainsilentwithnoreportsofclinicalBSEcasesformanyyears.Bythetimeafirstcaseisreported,theagentislikelywidespreadinthecattlepopulationandmanyanimalsarelikelyincubatingthedisease.
Data used TheGBRassessmentismainlybasedoncomprehensivenationalinformationprovidedbythecompetentauthoritieswithintheassessedcountries,anditisassumedthattheinformationprovidediscorrect.Sofar,theavailabledatahavegenerallybeenadequatetocarryoutaqualitativeassessmentof theGBR,butconsiderabledifferences in theavailabilityandqualityofdataremainofconcern.
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Limitations in data quality and completeness are still observed despite the use ofall available additional sources of information, such as reports from the missions ofthe Veterinary Inspection Services of the Food and Veterinary Office of the EuropeanCommissionandinternationaltradestatistics.Tocomplementinsufficientinformation,worstcaseassumptionsaregenerallyusedaslongastheyareregardedasreasonable.These“reasonableworstcaseassumptions”areusedwheneverextrapolation,interpo-lationorsimilarapproachesarenotpossible.Forexample,whenconflictingdatafromequallyreliablesourcesareavailable,theworseofthetwoisused.Inanotherexample,ashortcominginmanyGBRdossiersisinsufficientinformationoncompliancewiththepreventivemeasuresput inplaceby thecompetentnationalauthorities.Compliance,therefore,isoftenassumedtobeweak.
AnotherproblemwithregardtodatacomesfromtheslowdevelopmentoftheBSEepidemicduethelongincubationperiodofthedisease.Thisimpliesthatexportscouldalreadyhaveposedexternalchallengestoimportingcountries,evenwhenthemateri-alswereexportedmanyyearsbeforethefirstBSEcasewasrecognizedintheexportingcountry.Italsoimpliesthatdataforuptothepast20yearsmustbeincludedintheseriskassessments.
Risk of introduction of the BSE agent into a country Importsarefirstexaminedbecause,asstatedabove,theGBRassumesthattheBSE
FigurE 5
External challenge and domestic amplification cycle of BSE
Source:SSC(2000b)
National Border
Import of MBM Import of cattle
Cattle withBSE
Cattle withBSE
slaughteredCattle
exposed toBSE
DomesticMBM fedto cattle
BSE infective material rendered
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agentcouldonlybeintroducedintoacountrybyimportsofBSE-infectedcattleandtheimportofBSE-contaminatedMBM.Also,theGBRassumesthatthespreadofBSEwasinitiallythroughtheexportoflivecattleorMBMfromtheUK.
Ascattleborn inthemid-1970s intheUKwerepotentiallyaffected, importsdatingbacktothisperiodareincludedintheriskassessmentinvestigationifdataareavail-able.Also,since1990,othercountriesinadditiontotheUKhavereportedBSE;there-foreimportsfromthesecountriesmustalsobeconsideredasrisky,unlessadequatesafeguards had been implemented. The risk of introduction of the BSE agent into acountryisevaluatedwithreferencenotonlytoacountry’sownimportstatisticsbutalsototheexportstatisticsoftheUKandotherat-riskcountries.Thisprocedureallowsaninitialanalysistobeperformedtodeterminewhetheranypotentiallyinfectiousmaterial(“challenge”)mighthaveenteredacountryatanytime.
Thefollowingpointsmustbeconsidered:• TheassumedexternalchallengeresultingfromimportsfromtheUKduringthe
peakoftheBSEepidemicintheUKistakenasthepointofreference.• ThechallengeresultingfromimportsduringotherperiodsandfromotherBSE
riskcountriesisassessedinrelationtothisbaseline.• BSEriskcountriesareallcountriesthatarealreadyassessedasGBRIIIorIV(i.e.
casesarepresentorlikelytobepresentinthecountry;GRBriskcategoriesaredefinedbelow)orwhichhavenotifiedatleastonedomesticBSEcase.
• Challenge levels are defined as a function of imports from the UK at the timewhentheriskofBSEcontaminationwasregardedtobethehighest.
• ThesepointsareusedforlivecattleimportsfromtheUK:– Theperiod from1988 to1993waschosenas thehighest riskperiod for live
cattleimportsbecauseitcoversroughlyoneincubationperiodbeforethepeakinBSE incidence (1992/93), andbecausedataoncase incidence inUKbirthcohortsshowthatriskwasalreadyhighin1985/86and1986/87.Breedingcat-tlethatnormallyreachanageoffiveormoreyearsintheimportingcountryarenormallyexportedatanageofaround24months(e.g.aspregnantheifers).Keepingthisrange,therefore,appearedtobejustified.Additionally,thoughitmightbepossiblethattheriskcarriedbyimportsin1987wasslightlyunder-estimatedbyusingthisrange,itismaintainedtoensurecomparabilityofGBRresults.
– It isassumedthatduringthisperiodtheaverageBSEprevalenceof infectedanimalsinexportedcattlewasaround5%,i.e.of20animals,onecouldhavebeeninfected.Thevalueof5%isusedbecauseatnormalsurvivalprobabilitiesonlyoneinfivecalvesreachesanageoffiveyears.Asthecaseincidenceinthecriticalbirthcohortswasprobablyabout1%,atleast5%ofthecalvesinthatbirthcohortmusthavebeeninfected.
– Amoderateexternalchallenge isthendefinedasachallengeresultingfromimportofbetween20and100livecattlefromtheUKintheperiod1988-1993.Amoderateexternalchallengewouldthereforehavemadeitlikelythatatleastoneinfectedanimalwasimported.Theotherlevelsofexternalchallengewereestablishedwiththeintentionofindicatingsignificantdifferencesintheexter-nalchallenge.Theresultingscalemainlyservesasatooltoensureconsistentjudgmentoftheriskresultingfromimports,ratherthanprovidinganobjectivemeasureofthelevelofrisk.
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• ThesepointsareusedforimportofMBMfromtheUK:– TheperiodofhighestriskthatMBMimportedfromtheUKwascontaminated
withBSEwassetto1986-1990.Theriskpeakedin1988when“specifiedbovineoffal”(SBO,moreorlesssynonymoustoSRM)wasexcludedfromthehumanfoodchainbutwasstill includedinrenderingandfeedproductionintheUK.The risk was later reduced with the exclusion of SBO from rendering, andthereforefeed,attheendof1989.However,astheeffectiveimplementationofthatbanwasdelayedforsometime,theriskofMBMimportsisconsideredtoonlyhavedeclinedsince1990,andthenfurtherin1993,whentheSBObanhadbeenmoreeffectivelyimplemented.
Table1indicatesthattheimportofonetonofMBMisconsideredtoposethesamechallengeastheimportofoneliveanimal.Itisunlikelytobehigherbecausetheprob-abilitythatmorethanoneinfectedanimalwasincludedintheprocessingofeachtonofMBMisverylow,evenduringtheepidemicintheUK.ItisunlikelytobelowerbecauserenderingcanonlyreduceBSEinfectivitynoteliminateit.
GiventhemuchlowerincidencesinBSEriskcountriesotherthantheUK,orintheUKinotherperiods,itisassumedthattheriskcarriedbylivecattleexportedfromotherBSEriskcountriesorfromtheUKinotherperiodsismuchlower.Toreachthesamelevelofrisk,therefore,either100times(R2)or1000times(R1)morelivecattlemustbeimportedthanfromtheUKbetween1988and1993.ForMBM,10(R2)or100(R1)timesmoreMBMmustbeimportedthanfromtheUKbetween1986and1990torepresentasimilarexternalchallenge.
Available import/export statistics do not allow clear differentiation of the various
TABLE 1. Definition of external BSE challenge levels according to the geographical BSE risk assessment
Level of external challenge resulting from import of live cattle or mBm from the Uk or other BSE-risk countries
Level of Live cattle from the Uk Other mBm* (tons) import Other external 1���-1��3 Uk countries from the Uk Uk countries challenge (no. of heads) imports 1���-1��0
Extremelyhigh >10000 >10000
Veryhigh 1000–<10000 1000–<10000
High 100–<1000 100–<1000
Moderate 20–<100 20–<100
Low 10–<20 10–<20
Verylow 5–<10 5–<10
Negligible 0–<5 0–<5
*MBMreferstoMBM,MMBM,BMorGreavesbutnottocompositefeedthatcoludcontainit.Source:SSC(2003a)
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formsofprocessedanimalproteins thatare imported.Theyalsodonotdifferentiatebetweenthetypesofproductsorbetweenspeciesfromwhichproductsareproduced.The term “MBM” is therefore used in the context of the GBR as a term referring tomeatandbonemealassuch,aswellasmeatmeal,bonemealorgreavesmadefrommeat and offal. It is also synonymous to “flours, meal, pellets made from meat oroffalnotfitforhumanconsumption;greaves”(EUROSTAT,customcode230110)intheimport/exportcontext.Aslongasnoevidenceisprovidedtothecontrary,intheGBRitisassumedthat“MBM”isatleastpartlymadefromruminantmaterial.
Theexternalchallenge thatenters theBSE/cattlesystem in the importingcountryassociatedwith importedcattleorMBMalsodependsonwhat isdonewith thecat-tleafter import.Thekeyquestion iswhethertheBSEinfectivitythatcouldhavebeencarried by these imports did enter the internal BSE/cattle amplification system, asdescribedinFigure5,ornot.
InfectivityimportedvialivecattleonlyenterstheBSE/cattlesystemoftheimportingcountryiftheseanimalsdieorareslaughteredandrenderedintoMBMthatcouldreachcattleviathefeedchain. Ifrenderingof importedcattle isavoided,theexternalchal-lengeiseffectivelymanagedandthereisnoriskthatdomesticinfectionscouldresultfrom imported infected cattle. Another related factor is age at slaughter; importedanimalsslaughteredyoung(e.g.<24monthsofage)mayonlycarrya fractionof theinfectivityfoundinaclinicalcase.Importedcalvesthatareimmediatelyslaughteredorfattenedandslaughteredbefore twoyearsofage therefore representanegligibleorverylowexternalchallenge.
InfectivityimportedviaMBMenterstheBSE/cattlesystemwhenitisintegratedintofeedthatcouldreachcattle,beitintentionallyorviacrosscontamination.Thelatterispossibleduringtransport,infeedmillsandonfarms,andisdifficulttocontrolalthoughtheabilitytoavoidcrosscontaminationisessentialforthestabilityofaBSE/cattlesys-tem(seebelow). If importedMBMisreliablyonlyusedfornon-ruminants,e.g. inpetfood,itwouldnotrepresentanexternalchallenge.
In principle, it cannot be excluded that, under certain circumstances, even animportation of infectious material entering an unstable BSE/cattle system may haveno impact. This may happen if it is unintentionally eliminated, e.g. if contaminatedimportedMBMisallfedtopigsorpoultryanddoesnotreachcattle,evenifduringthatperiod feeding MBM to cattle was legally possible and generally done. However, theprinciplesofriskassessmentsrequirethatreasonableworstcasescenariosareusedwhenever thecontrarycannotbedemonstrated. In theGBR, therefore, it isassumedthatanyBSEexposurewithinanunstablesystemwouldresultindomesticcattlebeinginfectedwithBSE.
Risk of propagating the BSE agent in a country Whenriskyimportsarefoundtohaveoccurred,thestabilityofthesysteminthecoun-try,i.e.thesystem’sabilitytominimizetheexposureofcattle,istheninvestigated.ThisprimarilyrelatestotheusemadeofMBM,theusemadeofSRM,therenderingcondi-tionsandthefeedingsystems.Thefactorsassumedtobeabletopreventtheamplifica-tionofBSEinfectivityinthesystemarethefollowing:
SRm:WhathappenswithSRMafterslaughterisevaluated.Somematerial,suchasbrainandspinalcord,maycontainparticularlyhighconcentrationsoftheBSEagent.InBSE-infectedcattlethatapproachtheendoftheincubationperiod,between95and
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Risk assessment99%oftheinfectivityisconcentratedintheSRM.Removingthesefromthefeedcyclereduces theamountof infectivitybyup to two logs.However, smallbreachesof thismeasuremayaffectthisreductionsignificantly.Ifthesematerialsareusedforfurtherprocessingtoanimalfeed,thereisahighriskofamplificationoftheBSEagent.
The definition of SRM in a country should not only include slaughterhouse waste(by-products) but also fallen stock or cattle dead on arrival or condemned in antemorteminspection.IfBSEispresentinacattlepopulation,theprevalenceofinfectedcattleapproaching theendof theBSE incubationperiod issignificantlyhigher in thesubpopulationoffallenstockandemergencyslaughterthaninregularslaughter(seethe “Surveillance forBSE”chapterof thiscoursemanual).Hence,considering thesecarcassestobeSRMandexcludingthemfromthefeedchainreducestheriskofrecy-clingtheBSEagent.AswithotherSRM,however,evenoccasionalrenderingoffallenstockcouldposeariskbecause,inthiscase,theanimalcouldhavebeenapproachingtheendoftheincubationperiodandahighconcentrationofBSEinfectivitywouldthenentertherenderingprocessandlaterthefeedchain.
Therefore,ifanSRMban,includingriskcarcasses,isputinplaceatanearlystage,this increasesthestabilityof thesystem.The impactofSRMremoval isassessedbytheGBRasfollows:
• SRMremovalisconsideredtobe“OK”ifSRMarereliablyremovedfromimportedanddomesticcattleandfallenstockisalsoreliablyexcludedfromrenderingintofeed.
• SRM removal is considered to be “reasonably OK” if SRM from imported anddomesticcattleandfallenstockisnormallynotrenderedbuttheefficiencyand/orimplementationofthisisnotwelldocumented.
• SRMremovalisconsideredtobe“notOK”ifithastobeassumedthatSRMand/orfallenstockarenormallyrenderedintofeed.
Rendering:whathappenswithanimalby-productsandcadaversisevaluated.“Ren-dering” refers to the processing of animal remains or entire animals into processedanimalproteinsandrelatedby-productssuchasMBM,bonemeal,meatmeal,greaves,andtallow.
The BSE agent is extremely resistant to most physical and chemical inactivationmethods. Ithasbeenscientificallyproventhateventreatmentof infectedmaterialat133°Cwith3barsofpressure(ofsteamintheairlesssystem)for20minutesdoesnotcompletelyinactivatetheagentiftheinitialinfectiveloadwashigh,althoughthisproc-essisabletoreduceBSEinfectivitysignificantly(OIE,2005h).Itisalsocrucialthatthematerialtoberenderedhasamaximumparticlesizeof5cmandamoisturecontentofabout60%.Recentexperimentshaveshownthatresidualinfectivitycanbepresentalsowhenveryhightemperatureswereused.
Therefore,iftherenderingprocessisappropriate,orthereisnorenderingindustryandtheanimalby-productsandcadaversareburiedorincinerated,thisincreasesthestabilityofthesystem.TheimpactofrenderingisassessedbytheGBRasfollows:
• If all rendering plants that process ruminant materials reliably operate at the133°C/20min/3barstandard,theGBRassumes,forallpracticalpurposes,thatanyinfectivitywouldbereducedbyafactorofatleast1000.Underthisconditionrendering isconsideredas“OK”.Also, ifnorenderingtakesplace,rendering isconsideredtobe“OK”.
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• If only rendering plants that process high-risk material (i.e. SRM, fallen stock,condemnedmaterialsandanimalscondemnedinantemorteminspection)reli-ably operate at the above standard, rendering is considered to be “reasonablyOK”.
• Ifhighandlowriskmaterialisrenderedundersubstandardconditions,oriftheevidenceprovidedforthereliableapplicationofthestandardconditionsisinsuf-ficient,renderingisconsideredtobe“notOK”,evenifindividualrenderingplantsmightcomplywiththestandard.
Feeding:whetherfeedingofMBMtoruminantsoccursisevaluated.Inmanycoun-tries,animalshavetraditionallyneverbeenfedMBM.Butassumptionsonthissubjecthave tobe lookedatcritically,asBSEcaseshavebeendiagnosed inmanycountrieswhereitwasnotacustomarypracticetofeedMBMtocattle.
Ithastobeconsideredthat,evenwhennoMBMhasbeenfedtoruminants,theexpo-sureriskmaystillremainbecauseofcrosscontaminationandcrossfeeding.IfMBMisbannedforruminantfeedbutallowedinfeedforpigsandpoultry,andthesefeedsweremanufacturedinthesamemillsandtransportedbythesamevehiclesasrumi-nantfeeds,andifinappropriatefeedingpracticescannotberuledoutonfarms,theriskstillremains.TheriskislowerthanincountriesthathavenotprohibitedfeedingMBMto ruminants but it is still significant. This is demonstrated by the large numbers ofreportedBSEcasesthatwerebornaftertheimplementationoffeedbans(BABcases)andothermeasures.
IfnocontaminationoccurredandfeedingMBMtocattlewouldbecompletelyavoided,theonlyefficientBSEtransmissionrouteknownwouldbeblockedandnomorecasesshouldbeseen.TheimpactofMBMbansandfeedingisassessedbytheGBRasfol-lows:
• Feeding is considered to be “OK” if it is highly unlikely that any cattle receivedmammalianMBM(MMBM)atanytimeintheirlives.ThisassessmenthastotakeintoaccountdeliberatefeedingofmammalianMBMtocattleaswellasacciden-taladministration,e.g.duetocrosscontaminationofMBM-freecattlefeedwith(tracesof)MMBM.Feedingisconsideredtobe“OK”if,forexample,atotalfeedbantogetherwithcontrolsbyfeedsamplingareimplemented.
• IfdeliberatefeedingofMMBMtocattleisunlikely,e.g.becauseofafeedban,butcrosscontaminationcannotbeexcluded(e.g.nocontrolsbysamplinginplace),feedingisconsideredtobe“reasonablyOK”.
• Ifdeliberatefeedingislikelytooccur,evenonlyatcertainperiodsoftheyearorofthelifeofcertaincattle,orifcrosscontaminationofcattlefeedwithMMBMislikely,feedingisthenconsideredtobe“notOK”.
Therefore,theBSE/cattlesysteminacountryisconsideredtobe“optimallystable”ifrecyclingoftheagentispracticallyexcluded.Thisrequiresthatallthreemainstabilityfactors(SRMremoval,renderingandfeeding)areinplace,wellcontrolled,implementedandaudited, i.e.areassessedas “OK”. Ideallysuchasystemwouldalso integrateahighly effective BSE surveillance system, and control of all imported live cattle andfeedswouldhelptopreventapotentialexternalchallenge,i.e.importedBSE-infectedcattleorBSE-contaminatedMBMfromenteringtheBSE/cattlesystem.
Thedifferentcombinationsofthethreemainstabilityfactorsresultindifferentlevelsofstability,asshowninTable2.Inaneutrally-stablesystem,therecyclingrateoftheBSEagentwouldjustbehighenoughtomaintainthetotallevelofinfectivityonceintro-
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ducedintothesystem,i.e.thenumberofnewinfectionsinthecattlepopulationismoreorlessequaltothenumberofincubatingcattleleavingthesystem.
It should be understood that Table 2 is not meant to provide a semi-quantitativeassessment of stability but is rather meant to be guidance for ensuring consistentinterpretationofcomparabledata.Thisshouldensurethatsimilarsituationsarejudgedsimilarly.
GBR results and status of countriesOnthebasisofthisevaluation,countriesassessedarecategorizedintofourGBRlev-els:
• GBRI:highlyunlikelythatanyBSEinfectedcattlearepresent.• GBRII:thepresenceofanyBSEinfectedcattleisunlikely,butitcannotbeexclud-
ed.• GBRIII:thepresenceofBSEinfectedcattleislikelyor,ifcaseswerealreadydis-
covered,thenumberofBSEcasesidentifiedduringthelast12monthsisbelow100permillionadultcattle.
• GBRIV:morethan100BSEcasespermillionadultcattlewerediscoveredinthelast12months.
AsofJune2006,68countrieshavebeenassessed(Table3).Insomecases,thecoun-trieshaveconductedinternalBSEriskassessmentsandsubmittedthemtotheSSCforreviewaccordingtoGBRguidelines.
Somecountrieshavealreadybeenassessedforasecondtime.Incertaincasestheresult of the second assessment has deviated from the first one. In some countriesinitiallyassessedasGBRII,aBSEdomesticcasewasdetectedduetoenhancedsurveil-lance (e.g.Austria,Canada,Finland,Slovenia).Thereasonfor thisdeviationwashowthe external challenge was assessed. Before 2002, only imports from countries withreportedcasesweretakenintoaccount.Since2002,alsoimportsfromGBRIIIcountrieswithnoreportedcasesaretakenintoaccount.
Often,beforethedetectionofthefirstcasesinmany“BSE-free”countries,theGBRshowed that a risk could be present. Since 2000, 11 countries have detected a firstBSEcase.Ofthese,sixhadpreviouslybeenclassifiedasGBRIII(CzechRepublic,Ger-
TABLE 2. BSE stability levels, according to the GBR assessment
Stability Level Effect on most important stability factors BSE infectivity (SRm removal, rendering, feeding)
Optimallystable1 Veryfast All3“OK”.
Verystable Fast 2“OK”,one“reasonablyOK”.
Stable Slow 2“OK”and1“notOK”or 1“OK”and2“reasonablyOK”.
Neutrallystable Constant 3“reasonablyOK”or 1“OK”and1“reasonablyOK” and1or2“notOK”.
Unstable Slow 2“reasonablyOK”,1“notOK”.
Veryunstable Fast 1“reasonablyOK”,2“notOK”.
Extremelyunstable Veryfast Allthree“notOK”.
1 ”Optimally”shouldbeunderstoodas“asstableaspossibleaccordingtocurrentknowledge”.Source:SSC(2003a).
StableThesystemwillreduceBSEinfectivity
UnstableThesystemwillamplifyBSEinfectivity
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many,Italy,Poland,Slovakia,Spain).Moreover,Israeldetectedafirstcasebeforetheassessmentwasfinalized,whilethedraftreportalreadyindicatedGBRIII.Similarly,inDenmark, the first BSE case was detected shortly before the finalization of the SSCOpinionof6July2000,whichalreadyindicatedtheclassificationofDenmarkintoGBRlevelIII.
The success of the GBR shows that a scientifically-based, comprehensive riskassessmentmustbecarriedouttoestimatetheextentoftheBSEproblemincountries.Decisionsonpreventivemeasuresshouldbebasedonadetailedriskassessmentandcountriesshouldnotwaituntilthefirstcaseoccursbeforetakingpreventivemeasures.ThereremainmanycountrieswithanunknownBSErisk.Inordertominimizeimportrisksfromthesecountries, furtherriskassessmentsareneededtoevaluatetherealBSEdistributionworldwide.
NewresearchfindingsandexperiencesmadehavebeenfollowedbymodificationsoftheGBRmethod(SSC,2002a,b,c).EspeciallyafterdetectingBSEcasesoutsideEurope,afurtherrevisionofthemethodisnownecessaryandwillbecarriedout inthenearfuture.
3. ImpORT RISk ASSESSmENT FOR BSE ItisclearthatthemostefficientwaytopreventtheintroductionofBSE,oranynewdis-ease,intoacountryistocontroltheimportofcertainproductsfromcountriesatrisk.Asstatedinsection1.1ofthischapter,theSPSAgreementencouragesWTOMemberstobase theirmeasureson internationalstandards,guidelinesand recommendations, i.e.theTerrestrialAnimalHealthCodeoftheOIEinthecaseofanimalhealthandzoonoses.
ImportriskassessmentforBSEfollowsthesamebasicstepsasallothertypesofimportassessments,asdescribedinsection2ofthischapter.
TABLE 3. Results of the GBR assessments through 200�
GBR I: Argentina(I),Australia(I),Iceland,NewCaledonia,NewZealand(I),
Highlyunlikely Panama(I),Paraguay(I),Singapore,Uruguay(I),Vanuatu
GBR II: Botswana(I),Brazil(I),Colombia,CostaRica(II),ElSalvador(I),
Unlikelybutnotexcluded India,Kenya,Mauritius,Namibia(I),Nicaragua(I),Nigeria,Norway(I),
Pakistan,Sweden(II).Swaziland(I)
GBR III: Albania,Andorra,Austria,Belarus,Belgium,Bulgaria,Chile(I),
Likelybutnotconfirmedor Croatia,Denmark,Canada(II),Cyprus,CzechRepublic,Estonia,
confirmedatalowerlevel Finland,FormerYugoslavRepublicofMacedonia,France,Germany,
Greece,Hungary,Ireland,Israel,Italy,Latvia,Lithuania,Luxembourg,
Malta,Mexico,Poland,TheNetherlands,Romania,SanMarino,
SlovakRepublic,Slovenia,SouthAfrica,Spain,Switzerland,Turkey,USA(II)
GBR Iv: Portugal,UnitedKingdom
Confirmedatahigherlevel
Note:Countriesre-assessedasof2004haveformerGBRlevelinbrackets
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Risk assessment3.1. OIE recommendations regarding import of BSE risk productsTheaimof theOIETerrestrialAnimalHealthCode is toassurethesanitarysafetyofinternationaltradeinterrestrialanimalsandanimalproducts.Thisisachievedthroughthe detailing of health measures to be used by the veterinary authorities of import-ingandexportingcountriestoavoidthetransferofagentspathogenicforanimalsorhumans,whileavoidingunjustifiedsanitarybarriers.
AsneworupdatedBSEinformationbecomesavailable,theBSEchapterintheOIECodemaybeamended.Toobtainthemostcurrentrecommendations,theonlinever-sion of the code should always be consulted (http://www.oie.int/eng/normes/mcode/en_sommaire.htm).Inthefollowingparagraphs,someofthemainTSEimportrecom-mendationsofthe2005Codearesummarized(OIE2005d):
• Regardlessof theBSEstatusof theexportingcountry, the tradeofsomecom-modities,suchasmilkandmilkproducts,semenandembryos,hides,skins,pro-teinfreetallow,anddicalciumphosphate,aswellasgelatineorcollagenpreparedexclusivelyfromhidesandskins,shouldbeauthorizedwithoutrestriction.SinceMay2005,alsodebonedskeletalmeatfromcattleof30monthsorlessandcertainbloodandbloodproductsareincludedinthislist(withsomeadditionalconditionssuchasthebanofcertainstunningtechniques,antemortemandpostmorteminspectionandnocontaminationwithSRMand/orMRM).
• Ruminant-derivedMBMorcommoditiescontainingsuchproductsfromcountrieswithcontrolledorundeterminedBSEriskshouldnotbetraded.
• FortheinactivationofTSEagentsduringtheproductionofMBMcontainingrumi-nantproteins,thefollowingprocedureshouldbeused:therawmaterialshouldbereducedtoamaximumparticlesizeof50mmbeforeheating;therawmaterialshouldbeheatedundersaturatedsteamconditionstoatemperatureofnotlessthan133°Cforaminimumof20minutesatanabsolutepressureof3bar(OIE,2005b).
• Therecommendationsconcerningimportsofcattleareadaptedaccordingtotheriskstatusoftheexportingcountry.Themainrecommendationsforcattleselect-edforexportfromcountrieswithBSEriskarethattheyaresufficientlyidentifiedandarenot theoffspringof suspectedcases. Inaddition, theyhave tobebornafter thedateonwhich thebanon the feedingofruminantswithMBMderivedfromruminantswaseffectivelyenforced.Forexportingcountrieswithnegligiblerisktherearenoconditionsrecommended.
• Fortheimportofmeatandmeatproductsfromcattleover30monthsitisrecom-mendedthat,forexportingcountrieswithBSErisk,thefeedingofruminantswithMBMderivedfromruminantshasbeenbannedandthebanhasbeeneffectivelyenforced. Furthermore, an ante mortem inspection is recommended. ProductsincludingorcontaminatedwithSRMand/orMRMmustbeexcludedfromimpor-tation, except from countries with negligible BSE risk. The list of SRM variesaccordingtotheBSEstatus.
3.2. Import risk assessment considerationsIfacountrywishestoimplementmeasuresthatarestricterthanthoseoftheOIE,theymustproveonscientificgroundsthatthereisareasonfordoingso,i.e.strictermeas-uresmustbebasedonanimportriskassessment.
Thustheprincipalaimof importriskassessment istoprovide importingcountries
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with an objective and defensible assessment of the BSE risks associated with theimportationofcattleandcattleproducts.Theassessmentscanbequalitativeorquanti-tativeandmayaddressindividualriskorsocietalrisk.Theassessmentshouldbebasedonthefollowingcriteria:
• The assessment should be transparent, so that the exporting country is pro-videdwithclearreasonsfortheimpositionofanyimportconditionsorrefusaltoimport.
• There should be a reasoned relationship between the measures chosen and theriskassessment,sothattheresultsoftheriskassessmentsupportthemeasures.
• Wherethereissignificantuncertainty,aprecautionaryapproachmaybeadopted.However,themeasuresselectedmustneverthelessbebasedonriskassessmentthattakesaccountoftheavailablescientificinformation.Inthesecircumstancesthe measures should be reviewed as soon as additional information becomesavailable.Itisnotacceptablesimplytoconcludethat,becausethereissignificantuncertainty,measureswillbeselectedonthebasisofaprecautionaryapproach.Therationaleforselectingmeasuresmustbemadeapparent.
Frequently,inpractice,BSE-relatedimportmeasuresimposedbycountrieswithoutreportedBSEcaseshavebeenextremelyharshand inmostcasesnotbasedonsci-entificfindings.Often,theyweredefinedasabeinga“precautionaryapproach”.Sub-sequently,unjustifiedimportmeasureswereoftenstoppedaftertheoccurrenceofthefirstBSEcaseintheimportingcountry.
IntheseBSEimportriskassessments,notonlytheexposureriskforcattle(asintheGBR),butalsotheexposureriskforhumansmustbeaddressed.Therefore,allwaysbywhichpeoplecanbeexposedtoinfectivityshouldbeconsidered.Forexample,fromthefarm,possibleBSEexposuremayoccurviaslaughteredcattle,bovine-derivedproductsandby-products.Fromthe incinerator,possibleexposuremayoccurviaair,sewage,otherrawproductsandgroundcontamination.
Afterallthepathwayshavebeenconsidered,informationoneachpathwaymustbegathered.Forquantitativeassessments,thesedatashouldbequantitativeifpossible.Forexample,whenBSEexposurerisk fromingestionof food isassessed, itmustbeconsidered that whether BSE exposure results in infection depends on the exposedspeciesaswellasthetypeandamountofexposure.Ingeneral,BSEriskassessmentsonlyconsidertheinfectivityoftissuesfromcattlepotentiallyinfectedwithBSE,asthisistheonlyzoonoticTSEknowntodate.Inthisexample,inordertoestimatetheamountofpossibleexposure,fourparametersareevaluated:
• TheinfectivityofCNStissuesfromananimalwithclinicalBSEtoanotherbovine.Experimentstodate(primarilyconductedattheVeterinarylaboratoryAgency/inthe UK) have evaluated the infectivity from brains of clinically affected bovines.Results range from101 to103bovineoral ID50/g,butongoingexperimentsmayallowfurtherprecisionofthisrangeinthefuture(SSC,2002d).
• Therelativeinfectivityofnon-CNStissuesinananimalwithBSE.Theinfectivityofnon-CNStissues,evaluatedthroughpathogenesisstudies,ispresentedinthe“IntroductiontoTSEs”chapterofthiscoursemanual.
• Thedevelopmentof infectivitythroughtheincubationperiodofthedisease.ThedevelopmentofinfectivityinCNStissueshasbeenevaluatedthroughpathogen-esisstudies.Thefirst infectivitywasfoundat32monthspostoral infectionandnotat26months.Inanattackratestudyusingsimilardoses,ameanincubation
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Risk assessmenttimeof48monthswasdetermined.Usingthesenumbers,anexponentialgrowthcurvecanbeestimatedforthedevelopmentofinfectivitythroughouttheincuba-tionperiod(SSC,2002d).
• The cattle–human species barrier. When human exposure is being evaluated,thespeciesbarriermustbeconsidered,thoughbecausenotmuchinformationisavailablehere,thecattleexposuredose(bovineoralID50)isoftenused.However,itisprobablethattheBSEinfectivityislowerforhumans,andmayrangefrom10to10000timeslessthantheinfectivityforcattle(Raymondetal.,1997;SSC,1999;2000c).
Insummary,whenimportriskassessmentsforBSEareundertaken,awidevarietyof comprehensive information needs to be gathered. A good level of current scien-tificknowledgeisrequiredandaccuratedataonallpossibleexposurepathwaysinthecountrymustbeknown(i.e.slaughtertechniques,renderingindustryparameters,whatiseaten in thecountry,etc).Therefore, it isclear that inorder toensuresuchariskassessmentisvalid,adequatetimemustbeallowedforacarefulandcomprehensiveunderstandingofalltheparameters.
4. REFERENCESmurray N. 2001. Import risk analysis, animals and animal products. New Zealand Ministry of
AgricultureandForestry.WellingtonISBN040-478-07660-6
promED mail.2006.http://www.promedmail.org/
Raymond GJ, Hope J, kocisko DA, priola SA, Raymond LD, Bossers A, Ironside J, will RG, Chen
SG, petersen RB, Gambetti p, Rubenstein R, Smits mA, Lansbury pT Jr, Caughey B. 1997.
MolecularassessmentofthepotentialtransmissibilitiesofBSEandscrapietohumans.Nature388,285-288
Sandman p.2006.http://www.psandman.com/
SSC (Scientific Steering Committee of the European Commission).1999.OpinionoftheScientific
SteeringCommitteeonthehumanexposurerisk(HER)viafoodwithrespecttoBSE(adoptedon
10December1999).http://europa.eu.int/comm/food/fs/sc/ssc/out67_en.pdf
SSC. 2000a. Opinion of the Scientific Steering Committee on a method for assessing the
geographicalBSErisk(GBR)ofacountryorregion:http://europa.eu.int/comm/food/fs/sc/ssc/
out68_en.pdf
SSC.2000b.FinalopinionoftheScientificSteeringCommitteeonthegeographicalriskofbovine
spongiformencephalopathy(GBR).http://europa.eu.int/comm/food/fs/sc/ssc/out113_en.pdf)
SSC. 2000c. Opinion on oral exposure of humans to the BSE agent: infective dose and species
barrier (adopted by the Scientific Steering Committee at its meeting of 13-14 April 2000,
followingapublicconsultationviaInternetbetween6and27March2000).http://europa.eu.int/
comm/food/fs/sc/ssc/out79_en.pdf
SSC.2002a.Updatedopiniononthegeographicalriskofbovinespongiformencephalopathy(GBR).
http://europa.eu.int/comm/food/fs/sc/ssc/out243_en.pdf
SSC.2002b.OpiniononthegeographicalBSErisk(GBR)anditsevolutionovertimeintheEuropean
UnionMemberStates:http://europa.eu.int/comm/food/fs/sc/ssc/out249_en.pdf.
SSC.2002c.Updateoftheopiniononthegeographicalriskofbovinespongiformencephalopathy
(GBR).http://europa.eu.int/comm/food/fs/sc/ssc/out291_en.pdf
SSC. 2002d. Update of the opinion on TSE infectivity distribution in ruminant tissues (initially
adoptedbytheScientificSteeringCommitteeatitsmeetingof11-12January2002andamended
atitsmeetingof7-8November2002).http://europa.eu.int/comm/food/fs/sc/ssc/out296_en.pdf
Epidemiology,
surveillance and
risk assessment
for transmissible
spongiform
encephalopathies
10�
SSC. 2002e. Opinions on GBR in EU countries, 2002: http://europa.eu.int/comm/food/fs/bse/
scientific_advice02_en.html
SSC.2003a.Theassessmentofthegeographicalriskofbovinespongiformencephalopathycarried
out worldwide by the European Commission’s Scientific Steering Committee. http://europa.
eu.int/comm/food/fs/sc/ssc/out363_en.pdf
SSC.2003b.OpinionsonGBRinthirdcountries.http://europa.eu.int/comm/food/fs/bse/scientific_
advice03_en.html
OIE (world Organisation for Animal Health).2001.Conclusionsandkeyrecommendations.Joint
WHO/FAO/OIE Technical Consultation on BSE: public health, animal health and trade. http://
www.oie.int/eng/publicat/rapports/en_BSEWHO-FAO-OIE.htm
OIE. 2005a.Bovinespongiformencephalopathy.TerrestrialAnimalHealthCode,Chapter2.3.13.
http://www.oie.int/eng/normes/MCode/en_chapitre_2.3.13.htm
OIE.2005b.Generalconsiderations(riskanalysis).TerrestrialAnimalHealthCode,Chapter1.3.1.
http://www.oie.int/eng/normes/MCode/en_chapitre_1.3.1.htm
OIE. 2005c. Import risk analysis. Terrestrial Animal Health Code, Chapter 1.3.2. http://www.oie.
int/eng/normes/MCode/en_chapitre_1.3.2.htm
OIE. 2005d. Factors to consider in conducting the bovine spongiform encephalopathy risk
assessment recommended inchapter2.3.13.TerrestrialAnimalHealthCode,Appendix3.8.5.
http://www.oie.int/eng/normes/MCode/en_chapitre_3.8.5.htm
OIE.2005e.Surveillance forbovinespongiformencephalopathy.TerrestrialAnimalHealthCode,Appendix3.8.4.http://www.oie.int/eng/normes/MCode/en_chapitre_3.8.4.htm
OIE.2005f.DiseasesnotifiabletotheOIE.http://www.oie.int/eng/maladies/en_classification.htm
OIE.2005g.ResolutionNo.XXVII,Recognitionofthebovinespongiformencephalopathystatusof
membercountrieshttp://www.oie.int/eng/info/en_statesb.htm#List
OIE.2005h.Proceduresforthereductionofinfectivityoftransmissiblespongiformencephalopathy
agents.TerrestrialAnimalHealthCode,Appendix3.6.3.http://www.oie.int/eng/normes/MCode/
en_chapitre_3.6.3.htm
wTO (world Trade Organization).1994.AgreementonSanitaryandPhytosanitaryMeasures.Final
ActoftheUruguayRound,Article5.http://www.wto.org/english/docs_e/legal_e/15-sps.pdf
1AppENDIX
Authors and course contributors
111
Appendix 1
Authors and course contributors
AUTHORS AND COURSE CONTRIBUTORS
Christine Friedli SAFOSO,Berne,SwitzerlandDagmar Heim SwissFederalVeterinaryOffice,Berne,SwitzerlandUlrich kihm SAFOSO,Berne,SwitzerlandElizabeth mumford SAFOSO,Berne,SwitzerlandNoel murray CanadianFoodInspectionAgency,Ottawa,CanadaFrancesco proscia FAO,AnimalProductionandHealthDivision,Rome,Italymo Salman AnimalPopulationHealthInstitute,FortCollins,Colorado,USAAndrew Speedy FAO,AnimalProductionandHealthDivision,Rome,ItalyTorsten Seuberlich NeuroCenter,UniversityofBerne,Switzerland
Participantsfromthepartnercountrieshavealsocontributedsignificantlytotheproductionandtranslationofthecoursemanuals,andtomanyotheraspectsofthecourses.
2AppENDIX
Related background reading and web links*
*ThesereferencesandWeblinksrefertoallfourCapacityBuildingforSurveillanceand Prevention of BSE and Other Zoonotic Diseases project course manuals.Therefore,alldocumentsandlinksmaynotbeapplicabletothetopicscoveredinthismanual.
*ThesereferencesandWeblinksrefertoallfourCapacityBuildingforSurveillanceand Prevention of BSE and Other Zoonotic Diseases project course manuals.Therefore,alldocumentsandlinksmaynotbeapplicabletothetopicscoveredinthismanual.
11�
Appendix 2
Related background reading and web links
RELATED BACkGROUND READING AND wEB LINkS
TSE pages of selected ministries and other general data sourcesDepartment of Environment Food and Rural Affairs. United Kingdom, BSE homepage:
http://www.defra.gov.uk/animalh/bse/index.html
FAO. BSEpages:http://www.fao.org/ag/AGAinfo/subjects/en/health/bse/default.html
ministry of Agriculture of New Zealand. BSE homepage: http://www.biosecurity.govt.nz/
node/7650
Swiss Federal veterinary Office. BSE homepage: http://www.bvet.admin.ch/gesundheit_tiere/
01752/01804/02075/index.html?lang=de
TAFS.Positionpapers:http://www.tseandfoodsafety.org/startseite.htm
United States Department of Agriculture. Animal and Plant Health Inspection Service, BSE
homepage:http://www.aphis.usda.gov/lpa/issues/bse/bse.html
wHO.BSEpages:http://www.who.int/zoonoses/diseases/bse/en/
International standardsOIE. Bovine spongiform encephalopathy. Terrestrial Animal Health Code, Chapter 2.3.13. http://
www.oie.int/eng/normes/MCode/en_chapitre_2.3.13.htm
OIE. Factors to consider in conducting the bovine spongiform encephalopathy risk assessment
recommendedinchapter2.3.13.TerrestrialAnimalHealthCode,Appendix3.8.5.http://www.oie.
int/eng/normes/MCode/en_chapitre_3.8.5.htm
OIE.Surveillanceforbovinespongiformencephalopathy.TerrestrialAnimalHealthCode,Appendix
3.8.4.http://www.oie.int/eng/normes/MCode/en_chapitre_3.8.4.htm
OIE. Procedures for the reduction of infectivity of transmissible spongiform encephalopathy
agents.TerrestrialAnimalHealthCode,Appendix3.6.3.http://www.oie.int/eng/normes/MCode/
en_chapitre_3.6.3.htm
OIE.1994.AgreementonSanitaryandPhytosanitaryMeasures.FinalActoftheUruguayRound,Article5.http://www.wto.org/english/docs_e/legal_e/15-sps.pdf
BSE cases and risk EC. BSE testing results of member countries of the EU. http://europa.eu.int/comm/food/food/
biosafety/bse/mthly_reps_en.htm
OIE.NumberofreportedcasesofBSEworldwide.http://www.oie.int/eng/info/en_esbmonde.htm
OIE.ResolutionNo.XXVII,Recognitionofthebovinespongiformencephalopathystatusofmember
countrieshttp://www.oie.int/eng/info/en_statesb.htm#List
SSC. 2002. Opinion on TSE infectivity distribution in ruminant tissues (state of knowledge,
December2001).AdoptedbytheScientificSteeringCommitteeatitsmeetingof10-11January
2002.http://europa.eu.int/comm/food/fs/sc/ssc/out241_en.pdf
SSC.OpinionsoftheScientificSteeringCommitteeoftheEC.http://europa.eu.int/comm/food/fs/
sc/ssc/outcome_en.html
Epidemiology,
surveillance and
risk assessment
for transmissible
spongiform
encephalopathies
11�
measuresEU. 2002. Regulation No 1774/2002. Laying down health rules concerning animal by-products
not intended for human consumption. http://europa.eu.int/eur-lex/pri/en/oj/dat/2002/l_273/
l_27320021010en00010095.pdf
European Union Guidance Document for Regulation 1��4/2002. http://europa.eu.int/comm/food/
fs/bse/bse48_en.pdf
FAO. 2004. Good practices for the meat industry. FAO Animal Production and Health Manual
No. 2. Rome (also available at: ftp://ftp.fao.org/docrep/fao/007/y5454e/y5454e00.pdf).
FAO. 2004. protein sources for the animal feed industry. Proceedings of the FAO Expert
ConsultationandWorkshop,Bangkok,29April-3May2002.FAOAnimalProductionandHealth
ProceedingsNo.1.Rome(alsoavailableathttp://www.fao.org/documents/show_cdr.asp?url_)
file=/docrep/007/y5019e/y5019e00.htm
FAO. 2007. Management of transmissible spongiform encephalopathies in livestock feeds andfeeding.Coursemanual,ProjectCapacityBuildingforSurveillanceandPreventionofBSEandOtherZoonoticDiseases.Rome
FAO. 2007. Management of transmissible spongiform encephalopathies in meat production.Course manual, Project Capacity Building for Surveillance and Prevention of BSE and OtherZoonoticDiseases.Rome
Heim D, kihm U. 2003. Risk management of transmissible spongiform encephalopathies in
Europe.RevScitechOffintEpiz22(1),179-199
Heim D, mumford E.2005.ThefutureofBSEfromtheglobalperspective.MeatScience70:555-
562
Heim D, murray N.2004.Possibilities tomanage theBSEepidemic:cohortcullingversusherd
culling–experiencesinSwitzerland.In:Prions:achallengeforscience,medicineandthepublichealthsystem,2nded.EdsHFRabaneau,JCinatl,HWDoerr.Karger,Basel,Switzerland.pp
186-192
OIE.2005.DiseasesnotifiabletotheOIE.http://www.oie.int/eng/maladies/en_classification.htm
Render – The National magazine of Rendering. 2004. Rendering 101: Raw material, renderingprocess,andanimalby-products.http://www.rendermagazine.com/August2004/Rendering101.pdf
The BSE Inquiry. 2000.Thereport.TheinquiryintoBSEandvariantCJDintheUnitedKingdom,Volume13: Industryprocessesandcontrols,Chapter6,Rendering.http://www.bseinquiry.gov.
uk/report/volume13/chapter6.htm
DiagnosticsEFSA. 2006.EFSAScientific reportson theevaluationofBSE/TSE tests.http://www.efsa.eu.int/
science/tse_assessments/bse_tse/catindex_de.html
OIE. 2005. Bovine spongiform encephalopathy. Manual of diagnostic tests and vaccines forterrestrialanimals,Chapter2.3.13.http://www.oie.int/eng/normes/mmanual/A_00064.htm
Safar JG, Scott m, monaghan J, Deering C, Didorenko S, vergara J, Ball H, Legname G, Leclerc
E, Solforosi L, Serban H, Groth D, Burton DR, prusiner SB, williamson RA. 2002.Measuring
prionscausingbovinespongiformencephalopathyorchronicwastingdiseasebyimmunoassays
andtransgenicmice.NatBiotechnol20(11):1147-1150.
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Appendix 2
Related background reading and web links
SurveillanceCameron AR, Baldock FC. 1998. Two-stage sampling in surveys to substantiate freedom from
disease.PrevVetMed34:19-30
Salman mD.2003.AnimalDiseaseSurveillanceandSurveySystems.MethodsandApplications.
IowaStatePress,Ames,Iowa,USA
Scheaffer RL, mendenhall w, Ott L.1990.ElementarySurveySampling.DuxburyPress,Belmont
CA.
Clinical examinationBraun U, kihm U, pusterla N, Schönmann m.1997.Clinicalexaminationofcattlewithsuspected
bovinespongiformencephalopathy(BSE).SchweizArchTierheilk139:35-41(alsoavailableat:
http://www.bse.unizh.ch/english/examination/htmlsklinischer.htm)
Human prion diseasesDepartment of Health,UnitedKingdom.CJD-homepage:
http://www.dh.gov.uk/PolicyAndGuidance/HealthAndSocialCareTopics/CJD/fs/en
3AppENDIX
Glossary of technical terms and acronyms*
*ThisglossaryreferstoallfourCapacityBuildingforSurveillanceandPreventionofBSEandOtherZoonoticDiseasesprojectcoursemanuals.Therefore,alldocu-mentsandlinksmaynotbeapplicabletothetopicscoveredinthismanual.
3AppENDIX
Glossary of technical terms and acronyms*
*ThisglossaryreferstoallfourCapacityBuildingforSurveillanceandPreventionofBSEandOtherZoonoticDiseasesprojectcoursemanuals.Therefore,alldocu-mentsandlinksmaynotbeapplicabletothetopicscoveredinthismanual.
121
Appendix 3
Glossary of technical terms and acronyms
GLOSSARy OF TECHNICAL TERmS AND ACRONymS
AAFCO AssociationofAmericanFeedControlOfficials
Ab Antibody
AFIA AmericanFeedIndustryAssociation
Animal by-products Tissues and other materials (including fallen stock) dis-cardedattheslaughterhouse,whichgenerallygotoincin-eration,burialorrendering(dependingonthecountry)
Animal waste Animalby-products
Ante mortem Before death (generally refers to the period immediatelybeforeslaughter)
Ap Apparentprevalence
BAB Bornaftertheban;animalswithBSEthatwerebornafterimplementationofafeedban
BARB Bornafter the realban;animalswithBSE thatwerebornafter implementation of a comprehensive and effectively-enforcedfeedban
BSC Biosafetycabinet
BSE Bovinespongiformencephalopathy
BL Biosafetylevel
By-pass proteins Proteinsthatarenotdegradedintherumenbutaredigest-edinthesmallintestinetoprovideadditionalaminoacids
CCp Critical Control Point: a step in a production chain that isessential to prevent or eliminate a food safety hazard orreduceittoanacceptablelevelandatwhichacontrolcanbeapplied
CEN EuropanCommitteeforStandardization
CJD Creutzfeldt-JakobDisease
CNS Centralnervoussystem
Combinable crops Thoseabletobeharvestedwithacombine
Contaminants Materialsthatshouldnotbepresentinagivenproduct;e.g.rodents,birds,rodentdroppings,toxinsandmouldarecon-taminantsthatshouldnotbepresentinanylivestockfeed
Control (noun) The state wherein correct procedures are being followedandcriteriaarebeingmet(HACCPcontext)
Control (verb) Totakeallnecessaryactionstoensureandmaintaincom-pliancewithcriteriaestablishedinaHACCP(orothercon-trol)plan(HACCPcontext)
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Core fragment ThepartofPrPScthatisnotdigestedbyproteinaseK(alsocalledPrPRes)
Critical limit Acriterionthatseparatesacceptabilityfromunacceptability(e.g.duringaudits)
Cross contaminants Substancescarriedfromareasormaterialswheretheyarenotprohibitedtoareasormaterialswheretheyareprohib-ited
Cross feeding The feeding of a livestock group with prohibited feedsintendedforanotherlivestockgroup
Cp Crudeprotein
CwD Chronicwastingdisease.
DNA Deoxyribonucleic acid; the genetic material for all livingorganismsexceptbacteria
Downer cattle Cattletoosicktowalktoslaughter(definitiondiffersamongcountries)
EC EuropeanCommission
EFSA EuropeanFoodSafetyAuthority
ELISA Enzyme-linkedimmunosorbentassay
Emergency slaughter Slaughter cattle with clinical signs non-specific for BSE(definitiondiffersamongcountries)
Epitope Structuralpartofanantigenthatreactswithantibodies
Epitope demasking Processinwhichtheepitopebecomesavailableforantibodybinding(forexample,bydenaturation)
Essential amino acids Those that cannot be synthesized and therefore must beprovidedbythefeed/food
EU EuropeanUnion
Fallen stock Cattlethatdiedorwerekilledforunknownreasons(defini-tiondiffersamongcountries)
FAO FoodandAgricultureOrganizationoftheUnitedNations
FDA FoodandDrugAdministration(UnitedStatesofAmerica)
FEFAC EuropeanFeedManufacturers’Federation
FIFO Firstinfirstout;aproductionconcepttooptimizequality
Flushing batches Batchesof feedprocessedortransported in-betweenfeedbatchescontainingprohibitedandnon-prohibitedmaterials,andintendedtoremovetracesofprohibitedmaterialsfromtheequipment
FmD Foot-and-mouthdisease
FN False negatives; truly-diseased animals that test negativeonadiagnostictest
Fp Falsepositives;trulynondiseasedanimalsthattestpositiveonadiagnostictest
FSE Felinespongiformencephalopathy;TSEincats,believedtobecausedbyingestionoftheBSEagent.
123
Appendix 3
Glossary of technical terms and acronyms
GAFTA GrainandFeedTradeAssociation
GAp Goodagriculturalpractices
GBR GeographicalBSEriskassessment
GHp Goodhygienepractices
Gmp GoodManufacturingPractices
GmT Goodmicrobiologicaltechnique
Greaves Aproteinaceousby-productoftherenderingprocess
GTm GAFTATradersManual
H & E Haematoxylinandeosinstain
HACCp Hazard Analysis and Critical Control Points: a method toidentifyprocessstepswherea lossorsignificantdeviancefromtherequiredproductqualityandsafetycouldoccurifnotargetedcontrolisapplied
HACCp plan Adocumentprepared inaccordancewith theprinciplesofHACCPtoensurecontrolofhazardsthataresignificantforthesegmentoftheproductionunderconsideration
Hazard Abiological,chemicalorphysicalagentwiththepotentialtocauseanadversehealtheffect
Hazard analysis The process of collecting and evaluating information onhazardsandconditionsleadingtotheirpresencetodecidewhich are significant for the segment of the produc-tion under consideration and therefore which should beaddressedinthecontrol(orHACCP)plan
High quality protein Proteinsourcesthatmatchtherequirementsofaparticularspeciesorproductionclasswell
HpLC Highperformanceliquidchromatography
IAG EuropeanFeedMicroscopistsworkinggroup
IFIF InternationalFeedIndustryFederation
IHC Immunohistochemistry
Indigenous BSE case DomesticBSEcase;non-importedBSEcase
m+C Methioninepluscysteine;aminoacidsgenerallyconsideredtogether,becausecysteinecanbederivedfrommethionineinanimals
ISO InternationalOrganizationforStandardization
mammal Ananimalthatlactates;inthiscontext,livestockexcludingaquaticspeciesandpoultry
mBm Meatandbonemeal; thesolidproteinproductof theren-deringprocess
medulla oblongata Caudalportionofthebrainstem
mmBm Mammalianmeatandbonemeal
monitoring Anongoingprocessofspecificanimalhealthdatacollectionoveradefinedperiodoftime
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monogastric species Animalswithsimplestomachs(e.g.swine,poultry,horses,humans)
mOSS Monitoringandsurveillancesystem
mRm Mechanicallyrecoveredmeat
NIRC Nearinfraredcamera
NIRm Nearinfraredmicroscopy
NIRS Nearinfraredspectrography
Notifiable disease Adiseaseforwhichthereisanationallegalrequirementtoreportcasesandsuspectstoanofficialauthority
Obex Thepointonthemidlineofthedorsalsurfaceofthemedullaoblongata thatmarks thecaudalangleof the fourthbrainventricle;amarkerfortheregionofthebrainstemwheresomeof thepredilection areas forhistological lesionsandPrPSc deposition in BSE are located (such as the dorsalnucleusofthevagus)
OD Opticaldensity
OIE WorldOrganizationforAnimalHealth
OR Oddsratio
pathogenicity Ability of an organism to invade a host organism and tocausedisease
pCR Polymerasechainreaction
pithing The laceration of central nervous tissue by means of anelongated rod-shaped instrument introduced into the cra-nialcavityofslaughtercattleafterstunning.
pk Proteinase K; a serine proteinase that digests PrPC com-pletelybutPrPSconlypartiallyundercertainconditions
post mortem Afterdeath
prion InfectiousagentcausingTSE
proteolysis Cleavage of a protein by proteases; also referred to as“digestion”
prp Prion protein, encoded by the gene PRNP, expressed bymanycelltypesandmanyorganisms
prpBSE Resistant prion protein associated with bovine spongiformencephalopathy;alsocalledPrPSc
prpC Normalprionproteinfoundineukaryoticcells
prpRes Resistantprionproteincore remainingafterproteolysisofPrPScusingproteinaseK
prpSc Resistant prion protein associated with transmissiblespongiformencephalopathies,includingBSE
prpSens Normalprionproteinfoundineukaryoticcells;alsocalledPrPC
pv Predictivevalue
12�
Appendix 3
Glossary of technical terms and acronyms
Rapid test Test systems using immunological assays that detect thepresence of infectious agents in animal tissues or othermaterialswithinhours
RR Relativerisk
Ruminant species Animals with multichambered stomachs that allow bacte-rial fermentationof feedsprior to intestinaldigestion (e.g.cattle,sheep,goats,camellids)
Scrapie ATSEofsheepandgoats
SE Sensitivityofadiagnostictest
Segregation Undesirable separation of raw ingredients in a compoundfeedafterprocessing
SFT SwissInstituteofFeedTechnology
Sick slaughter Cattle with non-specific signs (definition differs amongcountries)
Sp Specificityofadiagnostictest
SpS Agreement AgreementontheApplicationofSanitaryandPhytosanitaryMeasures
SRm Specifiedriskmaterials;thoseanimaltissuesmostlikelytocontainTSEinfectivematerial
SSC Scientific Steering Committee of the European Commis-sion
Strip test Lateralflowimmunochromatographictestforrapiddetec-tionofproteinsinfeedsamples
Surveillance Extension of monitoring in which control or eradicationactionistakenonceapredefinedlevelofthehealth-relatedeventhasbeenreached
TAFS InternationalForumforTSEandFoodSafety
TBT Agreement AgreementonTechnicalBarrierstoTrade
Terrestrial animal In thiscontextall livestockexcludingaquaticspecies (e.g.poultry,ruminants,pigs,horses)
TmE Transmissibleminkencephalopathy
Tp Trueprevalence
Tracing Determiningwhereananimalorproductoriginatedorhasbeen
Tracking Following an animal or product forward through the sys-tem
TSE Transmissiblespongiformencephalopathy
Uk UnitedKingdomofGreatBritainandNorthernIreland
USA UnitedStatesofAmerica
vCJD Variant (or new variant) Creutzfeldt-Jakob disease ofhumans; believed to be caused by ingestion of the BSEagent
Epidemiology,
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risk assessment
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encephalopathies
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wB Westernblot
wHO WorldHealthOrganization
wTO WorldTradeOrganization
Additionaldefinitionscanbefoundin• the OIE Terrestrial Animal Code, Chapter 1.1.1. http://www.oie.int/eng/normes/
MCode/en_chapitre_1.1.1.htm• theFAO/WHOCodexAlimentarius“Currentofficialstandards”.http://www.codex-
alimentarius.net/web/standard_list.do?lang=en
4AppENDIX
project summary
12�
Appendix 4
project summary
pROJECT SUmmARy
ThiscourseisapartoftheprojectCapacityBuildingforSurveillanceandPreventionofBSEandOtherZoonoticDiseases.Theaimoftheprojectistobuildcapacity,establishpreventivemeasuresandanalyserisksforbovinespongiformencephalopathy(BSE),sothat,ultimately,partnercountriesareableeithertoprovethemselvestobeBSE-freeorareabletodecreasetheirBSErisktoanacceptablelevel.Governmentalandprivateveterinary services, diagnostic laboratories, and the livestock, food and animal feedindustrieswillbestrengthenedandsupported,andtechnicalcapacitybuiltateverystepalongthefoodproductionchain.Inthefuture,theknowledgegainedduringthisprojectcould be used by the countries to establish similar programmes for control of otherzoonoticfood-bornepathogens.
TheprojectisfundedbySwissgovernmentalagenciesandutilizesexpertiseavailableinSwitzerlandandworldwideandinfrastructureavailablefromtheFoodandAgricul-tureOrganizationoftheUnitedNations(FAO)toassistthegovernmentsofthepartnercountriestoachievetheproject’saim.TheexecutingagencyisSafeFoodSolutionsInc.(SAFOSO)ofBerne,Switzerland.
The direct project partner in each country is the National Veterinary Office. Thecountriescommitandpayasalary toat leastone individual,situated in theNationalVeterinaryOffice,toactasaNationalProjectCoordinator(NPC),committhreetraineespercourseandprovidethenecessaryinfrastructureforimplementationoftheprojectinthecountry.TheNPCisresponsibleforcoordinatingtheactivitiesoftheprojectwithinthecountry,includingofferingtrainingcourses,identifyingandorganizingtrainees,andpromotingcommunicationbetweentheproject,thegovernment,thescientificcommu-nityinthecountry,thelivestockandfoodindustries,andthepublic.Othercommitmentsby the countries include providing paid leave time for employees to attend courses,providing infrastructure and facilities for in-country courses, providing historical andcurrentdata(surveillancedata,animalmovementdata,import/exportrecords)andthestaffrequiredtoidentifythosedata,andprovidingadequatestaffforandfacilitatingtheinitialneedsassessmentandfinalcomprehensiveriskassessment.
ANationalProjectBoardineachoftheparticipatingcountriesregularlyevaluatestheoperationalprogressandneedsoftheproject,andprovidesaregularvenueforcom-municationamongtheprojectteam,nationalpartnersandstakeholders.ThisBoardiscomprisedoftheNPC,representativesofthenationalgovernment,aprojectrepresen-tative, the localFAOrepresentative,and localstakeholders fromprivate industryandtheveterinarycommunity.
ACTIvITIES OF THE pROJECT1. Thespecificneedsofeachparticipatingcountryareassessed.2. Comprehensive courses to “train the trainers” are provided in Switzerland (or
elsewhere)toselectedparticipantstoimproveunderstandingoftheepidemiologyofandrelevantriskfactorsforBSEandtodevelopspecificknowledgeandskillsforimplementingappropriatecontrols.
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Threetraineesfromeachcountry,aswellastheNPC,traveltoSwitzerland(orelse-where)toparticipateineachcourse.
Thecoursesare:• DiagnosticTechniquesfortransmissiblespongiformencephalopathies• Epidemiology, Surveillance and Risk Assessment for transmissible spongiform
encephalopathies• Transmissiblespongiformencephalopathiesmanagementinlivestockfeedsand
Feeding• TransmissiblespongiformencephalopathiesManagementinMeatProduction
Each course is preceded by an introduction to BSE covering the background oftransmissiblespongiformencephalopathies(TSE),BSE,biosafety,generalconceptsofepidemiologyandriskassessment,andriskcommunication.Eachcoursealsoincludesdiscussionofaspectsofriskcommunicationthatarerelevant to thetopicbeingpre-sented.
Onlythosemotivatedindividualswhowillbeimplementingtherelevantinformationinto the national BSE programme, who have some experience (e.g. ability to use amicroscope,veterinarytraining)andhaveadequateEnglishskills,areaccepted.
After each course, the relative success of the course is evaluated focusing on thesuccess of the training methods and effectiveness of the knowledge transfer ratherthanonthelearningoftheindividualtrainees.Therefore,nowrittentestisgiven,butclosecontact ismaintainedwiththetraineesaftertheyreturntotheircountries,andtheirprogressandsuccess in implementationof their training into thenationalBSEprogrammeisfollowedandevaluatedinthefield.
3. Eachof theTSE-specificcourses is thenofferedasan in-countrycourse in thenative language, and is organized by the trainees and the National VeterinaryOfficeswithtechnicalsupportfromtheproject.In-countrycoursesusethesamecurriculumandexpectedoutcomesastheoriginalcourses,andareprovidedwithsupport,technicalassistanceandmaterials(translatedintotheirownlanguage).TheintroductoryTSEandbiosafetycoursecurriculumisalsopresented.Atleastoneexpert trainerassists inpresenting thesecourses.Participantsarechosenaccordingtostrictselectioncriteria,butthenumberofparticipantsandthefre-quencyandlocationofcoursesgivendependsontheneedsofthecountryandthetypeofcourse.
4. The knowledge gained through the courses should then be integrated by thepartnercountrythroughdevelopmentandimplementationofanationalBSEcon-trolprogramme.Theprogrammeispromotedandsupportedbythecountriestoensurethesustainabilityofthesystem.Contact,technicalsupportandfollow-upwiththecountriesisongoingthroughouttheproject.
5. InformationcampaignstoimproveBSEawarenessaretargetedtonationalgov-ernments,producersandconsumers.
6. PartnercountriesaresupportedinthesubmissionofacomprehensivenationalBSEriskassessmenttotheWorldOrganisationforAnimalHealth(OIE)inordertodocumenttheirBSEstatustotheinternationalcommunity.
