Application of discrete choice experiment to assess farmers’ willingness to report swine diseases in the Red River Delta region, Vietnam

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Contents lists available atScienceDirect

Preventive

Veterinary

Medicine

j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / p r e v e t m e d

Application

of

discrete

choice

experiment

to

assess

farmers’

willingness

to

report

swine

diseases

in

the

Red

River

Delta

region,

Vietnam

Hoa

T.T.

Pham

a,∗

_,

_Marisa

_Peyre

b

_,

_Tuyen

_Quang

_Trinh

c

_,

_Oanh

_Cong

_Nguyen

d

_,

Ton

Dinh

Vu

d

_,

_Theera

_Rukkwamsuk

e

_,

_Nicolas

_{Antoine-Moussiaux}

f

a_French_Agricultural_Research_Center_for_{International}_Development_(CIRAD),_Van_Phuc_Diplomatic_Compound,₂₉₈_Kim_Ma,_Ba_Dinh,_Hanoi,_Vietnam

b_French_Agricultural_Research_Center_for_{International}_Development_(CIRAD),_Animal_and_Integrated_Risk_Management_Research_Unit_(AGIRs),₃₄₃₉₈

Montpellier,France

c_National_Institute_of_Animal_Science,_Hanoi,_Vietnam

d_Center_for_{Interdisciplinary}_Research_on_Rural_Development_(CIRRD),_Vietnam_National_University_of_Agriculture,_Hanoi,_Vietnam

e_Kasetsart_University,_Bangkok,_Thailand

f_Fundamental_and_Applied_Research_for_Animals_&_Health_(FARAH),_University_of_Liège,_Belgium

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received27September2016 Accepted2January2017 Keywords: Swinediseases Willingnesstoreport Surveillance Control

Discretechoiceexperiment

Vietnam

a

b

s

t

r

a

c

t

Adiscretechoiceexperiment(DCE)iscarriedouttovaluesocio-economicfactorsinfluencingthefarmer’s decisiontoreportswinediseasesandtoassessthewillingnessoffarmerstoreportswinediseases. DatawerecollectedbetweenMarchandJuly2015intwoprovincesintheRedRiverDelta,Northern Vietnam,from196pigproducersbyface-tofaceinterview.Aconditionallogitmodelisusedtomeasure therelativeimportanceofthesocio-economicfactorsandcalculatetheexpectedprobabilityofdisease reportingunderchangesoflevelsofthesefactors.Resultsofthestudyindicatedthatthelikelihood ofcompensationandthetypeofcullingimplemented(alloronlyunrecoveredpigs)arethetwomost importantfactorsinfluencingfarmerreporting.Compensationlevel,movementrestrictionanddelay incompensationpaymentalsohavesignificantimpactsonfarmer’sdecisiontoreportanimaldisease buttheyarenotasimportantastheabovefactors.Threedifferentscenariosincludingchangesinsix differentfactors(attributes)aretestedtopredictprobabilityofanimaldiseasereporting.Underthe currentsituation(uncertaintyofbeingcompensated),only4%ofthefarmerswouldreportswinedisease outbreaktotheofficialsurveillancesystemifthecullingpolicyinvolvesallpigsinaffectedfarms.This numberisincreasedto26%ifcullinginaffectedfarmsisrestrictedtounrecoveredpigsonly.Ensuring certaintyofcompensationincreasesreportingprobabilitybyupto50%and90%ifalloronlyunrecovered pigsaredestroyed,respectively.Theresultsofthisstudyareimportantforimprovingtheperformance andsustainabilityofswinediseasesurveillancesysteminVietnam.

1. Introduction

Passivesurveillanceisaprocesswherebyanimalhealth infor-mation is collected regularly from different sources such as diseasereportingby livestockowners, ﬁeldveterinarians, labo-ratorydiagnosticreports, slaughterhouses and livestockmarket records(Geeringetal.,1999).Farmers’reportingofanimaldisease playsanimportantroleinthenationalsurveillancesystemdue totheirabilitytodetectawiderangeofdiseases,theirextensive

∗ Correspondingauthor.

E-mailaddress:thithanhhoapham@ymail.com(H.T.T.Pham).

coverageoftheanimalpopulation,andtheirfrequentcontactwith animals(Cameron,2012).Theresultsofastudycomparingthree datasources ofdairy diseasesurveillancein NewZealand indi-catedthatfarmersrecordedthehighestnumberofdiseaseevents (14.6per1000cowmonthsatrisk)comparedtoveterinary prac-tices(5.2per1000cowmonthsatrisk)anddiagnosticlaboratories (0.6per1000cowmonths)(McIntyreetal.,2003).However,the willingnessoflivestockownerstoshareanimalhealthinformation withveterinaryauthoritiesisinﬂuencedbymanysocio-economic factors.Cameron(2012)proposedthatfearofthenegative conse-quencesofdiseasenotiﬁcation,poorrelationshipwithveterinary services,andfarmers’apathytowarddiseaseoccurrenceand con-trolarethemainreasonsfor farmersfailingtoreport(Cameron, http://dx.doi.org/10.1016/j.prevetmed.2017.01.002

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2012).Theresultsofasocio-psychologicalstudyamongpigfarmers in theNetherlands indicated that uncertainty aboutthe occur-renceofa given diseaseand thethreatof afalse alarm, which mighthaveanegativeimpactonthefarmandontherelationship betweenfarmersandveterinarians,wereimportantfactors inﬂu-encingfarmerreporting(Elbersetal.,2010).Lackoftrustinthe control/eradicationmeasuresofveterinaryauthoritiesisalso con-sideredasabarriertofarmers’willingnesstoreport(Elbersetal., 2010;Palmeretal.,2009).Hadornetal.(2008)indicatedthatthe diseaseawarenessoffarmersisanimportantfactorinﬂuencingthe sensitivityofpassivesurveillanceandthatinendemicareas,where animalownersarelikelytobeawareofthedisease,the probabil-ityofdiseasereportinganddetectionseemstobehigherthanin areaswherethediseaseisunknownorneglected(Hadornetal., 2008).Understandingthese socio-economicfactorsiscritical for improvingtheeffectivenessofpassivesurveillancesystems.

Variousinterventionshavebeensuggestedtoimprovethe per-formanceofpassivesurveillancesystemsbasedontheinvestigated farmer’sattitudeandbehaviorinanimaldiseasereporting(Bronner etal.,2014;Dungetal.,2006;Elbersetal.,2010;HadornandStärk, 2008;Palmeretal.,2009).Themostusedmethodsareenhancing publicawareness ofpriorityanimal diseases andof the impor-tanceof earlyreporting throughmassmedia,theimprovement ofrelationshipsbetweenfarmers andveterinarystaff,provision ofincentivesforreporting,andprovisionofappropriate compen-sationforcullinganimals(Cameron,2012).Gilbertetal.(2012) suggestedasubsidyforcarcasscollectionandtelephone consul-tationsforprivateveterinariansastwosolutionstoincreasethe cost-effectivenessofpassivesurveillance(Gilbertetal.,2012). Pos-siblesolutionssuggested toimproveanimal healthsurveillance inVietnamincludetravelallowancesfordistrictveterinariansto facilitatefieldvisitingandcommunicationwithfarmers,commune para-veterinariansanddrugvendors,andimprovingdata analy-siscapacityatlocallevel(i.e.districtandprovincialoffices)(Dung etal.,2006).Inthecontextofendemicdiseases,tomaintainthe interestandmotivationoffieldactorssuchasfarmersandlocal veterinarianstoreportanimaldisease,animalhealthinformation needstobecommunicatedtothepartnerstoshowlivestock own-ersandlocalveterinariansthedirectbenefitsoftheirparticipation inthesurveillancenetwork(Doherretal.,2012).Anexampleof reinforcingpassivesurveillanceinSouthAustraliathrough subsi-diestolaboratorytesting,incentivesforprivateveterinariansin datacollection,andtheraisingoffarmers’awarenessofthebenefits ofsurveillanceactivitiesresultedinsignificantlyincreasingsample submissionrate(Cliftetal.,2006).Mostofthesestudieswerebased ona qualitativeapproachtoidentifythefactorsinfluencingthe decision-makingprocess.Toourknowledge,onlyalimitednumber ofstudies(Limonetal.,2012;Palmer,2009)haveusedquantitative approachestoassessthesocio-economicfactorsinfluencingfarmer reporting.

Statedpreferencemethodsareasetofdifferenteconometric methodstocharacterizeconsumerpreferencesincaseswhere mar-ketscannotbeobserved.Theyhavebeenwidelyusedinmarketing (Lagerkvist etal., 2006; Thongand Hung, 2014;Xu and Wang, 2014),transport,andenvironmentaleconomics(Adamowiczetal., 1994;Boxalletal.,1996;Hanleyetal.,1998;ZanderandGarnett, 2011),aswellashealth economics(Howardand Salkeld,2009; Raoetal.,2013;Sadiqueetal.,2013).Morerecently,theyhave alsobeen appliedtoanimal scienceand animal health. Among thedifferenttypesofstatedpreferencemethods,discretechoice experiments(DCE)aremoreparticularlyappliedtoinvestigating consumerpreferencesforparticularqualities(calledattributes)of theproductorservice.Assuch,theyprovidequantitative informa-tiononstrengthofpreference,thetrade-offbetweenthefactors affectingthispreference,andtheprobabilityoftakeupofa prod-uct,serviceorinnovation(WHO,2012).Regardinganimalproducts,

theyhavebeenmobilizedtoquantifythedemandforunobservable attributes,suchasanimalwelfareattributes(Lagerkvistetal.,2006; Liljenstolpe,2005).DCEisalsousedtoidentifyandevaluate farm-ers’decisionsregardinganimal diseasereporting(Oparindeand Birol,2011)andanimaldiseasecontrolmeasures(Otiennoetal., 2011;Zhangetal.,2014).

Theobjectivesofthisworkaretomeasuretherelative impor-tanceofsocio-economicfactorsthatinﬂuencethefarmer’sdecision toreportdisease,andtoassessthefarmer’swillingnesstoreport animaldiseases.Theresultsofthisstudyhighlightthefactorsthat needtobeimprovedandtowhatextent,inordertoimprovethe probabilityofanimaldiseasereporting.

2. Materialandmethods

In this study, theDCE is used to explore farmer’s choicein regardtoanimaldiseasereportinguponoutbreakonhis/herfarm. This approach waschosen as it allows quantitatively assessing therelativeimportanceoffactorsinfluencingfarmer’sbehavioror decisionmakingandevaluatingthefamer’swillingnesstoreport intermsofpredicteduptakeunderthechangesofthesefactors (attributes).Farmer’spreferenceforanimaldiseasereportingwas elicitedbypresentingthemanumberofhypotheticalchoicesthat wereconstructedbyvaryingcombinationsofattributelevels(i.e. characteristicsofdiseasenotificationandcontrolprocedures). Par-ticipantswererequiredtoselectoneofthealternativesineach choice-setaccordingtotheirpreference.TheDCEmodelisbased onrandomutilitytheoryundertheassumptionthatthefarmer chooses the alternative that provides the highest benefit (util-ity) (McFadden, 1974).Statistical analysis of theresponse data allows toestimatehowmuch each alternativeis preferredand whichattributescontributemosttothechoice.Monetaryunitcan beincludedasoneattributeinDCEandthecombinationofcost dataprovidesanassessmentofthecost-effectivenessof alterna-tiveoptions(Kjaer,2005).Percentageoffarmer’s willingnessto reportanimaldiseasesispredictedbymodelingtheprobabilityof choosinganalternativewithspecifiedcharacteristics(attributes) ofdiseasenotificationandcontrol.Suchinformationisacritical pointofthisstudy.

ToconductDCE,anumberofdistinctstagessuchas identiﬁ-cationofattributesandassignmentofattributelevels,designand constructionofchoicesetstopresenttoparticipants,development questionnaire,datacollection,anddataanalysiswereimplemented step-by-step.ThelinksbetweenstepsarecrucialasresultsofDCE arehighlysensitivetothesystematicandwelldesignofthewhole experiment(WHO,2012).

2.1. Identiﬁcationofattributesandassignmentoflevels

Atotalof18focusgroupdiscussionswithpigfarmersand key-informantinterviewswerecarriedoutintwoprovinces.Thetopics tackledwereswinediseases,diseasepriorityforsurveillanceand control,aswellasfactorsinfluencingthefarmer’sdecisiontoreport swinedisease.Fromtheresultsofgroupdiscussionsandkey infor-mantinterviews,sixattributeswereidentifiedandincludedinthe discretechoiceexperimentasfollow:(1)Uncertaintyofbeing com-pensatedincase ofanimal diseasereporting;(2) Compensation levelsincaseofanimalculling(priceperkgofpigbodyweight); (3)pigcullingincaseofdiseasereporting;(4)administrative pro-cedurefordiseasenotificationandgettingcompensationpayment; (5)movementcontrolincaseofdiseasenotification;(6)delivery timeofcompensationpayment.

Attribute levelswerethen assigned onthebasis of the sur-veyresultsandfromaliteraturereviewonveterinaryregulations (MARD,2008,2007)inVietnam.Theattributesandattribute

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lev-Table1

Attributesandattributelevelsusedinchoiceexperiment.

Attribute Levels Probabilityofbeing compensated Uncertain Certain Compensationlevel VND24000/kgLBW VND33600/kgLBW VND38400/kgLBW Animalcullingpolicy Unrecoveredpigs

Allpigsatfarm Administrativeproceduresof

diseasereportingand compensationpayment

Simple

Complicate Movementcontrolinoutbreak

area

Nomovementban Movementban Deliverytimeofcompensation

payment

3months 6months 1year (LBW:livebodyweight).

elsusedinthechoiceexperimentaredescribedinTable1.Detail

descriptionsofattributelevelsarepresentedinAFTable1. Com-pensationlevelisaddedasamonetaryattributeandexpressedas apercentageofthemarketpriceforthelivebodyweight(LBW) ofafatteningpig,whichis thenconvertedintoacompensation price(i.e.amountofmoneyperkilogramLBWofcullingpig)using aﬁxedmarketpriceofVND48,000kgLBW.Thispricewas consid-eredasmeanvaluesofpigpricesbetween2010and2013thatwere collectedduringfocusgroupdiscussionandkey-informant inter-views.Compensationattributelevelsweresetat50%,70%,and80% ofpigmarketpriceperkgLBW.

2.2. Experimentdesign

AfractionalfactorialdesignwasusedwithRsoftwareversion 2.15.3(Rcoreteam,2013)(support.CEspackage).Anunlabeled choice experiment design was created by the mix-and-match method(rotation.designfunction).Achoicesetwasgeneratedby randomlyselectingonealternativefromeachsetofNalternatives. Theselectionprocesswasrepeatedwithoutreplacementuntilall alternativeswereassignedtochoicesets(Aizaki,2012).The num-berof36 choicesetsof twoalternativeswassuggestedfromR output.Giventhenumber ofattributesand levels,this number helpstoensurethatthedesignisorthogonalandbalanced(Kuhfeld, 2010).Tolimittheburdenforrespondents,itwasdividedintothree blocksof12choicesets.

2.3. Questionnairesanddatacollectionprocess

Questionnaireswerecreatedbasedonthechoicesetsusingthe questionnairefunction in thesupport.CEspackage in R(Aizaki, 2012).Eachfarmerwasaskedtoanswer12questionsequivalent to12choicesetsinoneblock.Eachchoicesetconsistedoftwo unlabeleddisease-reportingalternativesandoneopt-out alterna-tive(non-reportingalternative).Farmerswereaskedtoconsider thesethreealternativesandchoosetheoptionthatthey consid-eredthebestfortheirsituation.Includingopt-outoption which referas“donotreport”or“donotchooseanyalternative”inchoice setsallowedustolimitthebiasoftheforcedchoiceandexplore thereasonsbehindfarmer’sdecision.

2.3.1. Studyareaandsamplingframe

TheDECsurveywasconductedbetweenMarchandJuly2015 in eight communes of four districts of two Red River Delta provincesbyface-to-faceinterviewsinVietnamese.Theselection ofprovinces,districtsand communeswasbasedonpigdensity, extentof pigproduction, diversity of pigfarming systems, and occurrenceofnotifiedswineinfectiousdiseases(e.g.porcine repro-ductiveandrespiratorysyndrome(PRRS),footandmouthdisease (FMD),andclassicalswinefever(CSF)).Thetwoprovincesare sub-sequentlyreferredtointhispaperasprovince“A”andprovince“B” aspartoftheconfidentialityproceduretoensureanonymoususe ofthedata.Stratifiedrandomsamplingwascarriedoutbasedon productiontypes(mixedfarm,fatteningfarm)andproduction sys-tems(smallorlargefarm,basedonathresholdof20sowsand/or 200fatteningpigs).Thelistofpigfarmersineachcommunewas obtainedfromcommuneveterinarians.Itwasthenstratifiedinto theabove-mentionedcategories.Pigfarmers wereselected ran-domlyfromthecategoriesandinvitedtoparticipateinthestudy withthesupportofthecommuneveterinarianandtheheadofthe village.Duetothelimitednumberoflargefarmsinthestudyarea, alllargefarmsweresubjectedtointerviews.

EquationstocomputesamplesizeforDCErequiresaninitial estimationofchoiceproportion(BliemerandRose,2005)orprior estimates ofparameter values ofattributes under investigation (Bekker-Grobetal.,2015)whichareunknownbefore implement-ingthestudy.Therefore,samplesizecalculationinthisresearch isbasedonOrme’sapproachthatconsidersthenumberofchoice sets,thenumberofattributes,andthehighestnumberofattribute levels(Orme,2009).Targetsamplesizewas120pigholdingsin eachprovince(30largefarmsand90smallholders),includingboth fatteningandmixedfarmswiththeratio(1:5)likethatof fatten-ingholdingsandmixedholdingsinarea.AccordingtotheWHO guidelineondiscretechoiceexperimentsinpublichealthresearch, aminimumsamplesizeof30isrequiredforeachsubgroup (strat-iﬁedgroup)ofthemainsampletoperformeconometricanalysis (WHO,2012).

2.3.2. Datacollection

TheDCEtaskstartedbysettingouttheobjectivesofthestudy, theimportanceofthefarmers’contribution,thesecurityof per-sonalinformationandtheiroralconsenttoparticipateinthestudy. Thenascenarioofdiseaseoccurrenceonthefarmwasdescribed tocreateacontextinwhichthefarmerscouldmaketheirdecision (Table2).Detaileddescriptionsofchoicesetsaswellasattributes weremadetoensureaclearunderstandingofthechoiceprocess. Probingquestionswereusedtoexplorerelatedinformationsuchas thepossibilityofsellingsick/deadpigs,priceofsickpigsaswellas thefarmer’sperceptionofmoneyobtainedinthecaseofreporting ornotreporting.Thequestionnairesweretestedwith17pig hold-ersandwereadjustedtoadapttoﬁeldconditionssuchasspecifying infectedpigagegroupsandthethresholdpercentageofinfected pigsinthefarmtriggeringdiseasereporting.

Generalinformation wasalsocollectedduringtheinterview abouttherespondents,suchasage,education,position,andabout thepigfarms(herdsize,productionsystem).

2.4. Dataanalysis

McFadenconditionallogitmodelwasusedtoanalysisDCEdata inthisstudyasthemodeldescribesthecharacteristics(attribute andattributelevels)ofthealternativesamongwhichthefarmer choosetoreportanimaldiseaseandrequiresthesmallestsample sizecomparedtoothermodels(Hauberetal.,2016).Thesystematic utility(Vi)boundtoascenariowasmodeledasalinearfunctionof attributelevelscharacterizingthescenario.Theexpressionofthe

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Table2

Anexampleofchoiceset.

Imaginethatmorethan40%ofyourpigsaresickwithclinicalsignsassuspectedcasesfromoneofthethreenotiﬁeddiseases(PRRS,FMD,andCSF).Yoursick pigsdidnotrespondafter3–5daysoftreatmentandtheliveweightoffatteningpigsrangedfrom20to50kg.Chooseoneofthefollowingoptionsrelatedto diseasereportingtoreportswinediseaseinyourholdingtoveterinaryorlocalauthorities.

Choiceset1 AlternativeA AlternativeB NeitheralternativeAorB

Probabilityofbeing compensated 100%(certain) 50%(uncertain) Compensationlevel (VND/kgofLBW) 24,000 (50%marketprice) 33,600 (70%marketprice) Animalculledincaseof

diseasenotiﬁcation

Unrecoveredpigs Allpigsatfarm Idonotwanttoreportswinedisease Diseasereportingand

compensation procedures Simple Complicate Animalmovement controlinoutbreak area Animalmovement ban Noanimalmovement ban Deliverytimeof compensation payment 3months 6months

Yourchoice(Pleasetick onlyoneboxasyour preference)

䊐䊐䊐

utilitymodelisasfollows:

Vi= ␤0+␤1∗possibilitycompensation+␤2∗compensation

+␤3∗animaldes+␤4∗administrativeprocedureof

diseasereportingandcompensation+␤5∗movementban+␤

6∗deliverycompensation+␧ (1)

The utility coefﬁcients (␤1–␤6)were calculated using clogit

functioninthesupport.CEspackageinR(Aizaki,2012).

Qualita-tiveattributeswerecodedasdummyvariables,andthemonetary parameter (i.e. compensation levels) as a continuous variable. Parameterestimationwasrunseparatelyforthetotalsampleand thenaccordingtoprovince(AandB)andproductionsystem(small vs.large,mixedvs.fattening).Thegoodness-of-fitofthemodels ismeasuredusingMcFadenpseudo-Rsquared(p2₎_which_can_be definedbytheloglikelihoodsofthemodelwithandwithout pre-dictors.Valuesfrom0.2to0.4forp2 _indicate_the_good_fit_of_the model(McFadden,1977).

Therelativeimportanceofthesocio-economicfactors influenc-ingfarmers’reportingwasassessedbasedonresultsoftheutility model(i.e.thestatisticalsignificance,signandvalueofthe util-itycoefficientsofattributesandthewillingnesstopayforchanges inattributelevels)(WHO,2012).Thefarmers’willingnesstopay (WTPkl)for levellof anattribute kwascalculated astheratio betweenitsutilitycoefficient␤klandthemarginalutility coeffi-cientof compensation(utilitycoefficientof themonetaryunit). Theeffects of changesonsurveillance werethen modeledas a probabilityofchoosingreportingalternativeunderthreedefined scenarios.Theprobabilityofchoosingthereportingalternativewas estimatedaccordingto changesof attributelevels comparedto baselines.Threebaselinesweresetup,whichdifferedinregardto culledpigcategoriesandcompensationlevels.Thefirsttwo base-linesreferredtothecurrentsituationofswinediseasesurveillance andcontrolinVietnam(MARD,2008,2007):i)cullingofallpigsat infectedholdings(uponfirstoutbreakintheregion),ii)cullingof unrecoveredpigsonly(uponre-occurrenceinthearea).Thethird baselinewasestablishedasanunrealisticscenariowiththe com-pensationlevelat50%ofthemarketvalueofthepiganddestroying dead/unrecoveredpigsonly.Thefulldescriptionsofthethree base-linesareasfollows:

–Baseline1:uncertaintyofbeingcompensated,cullingallpigsat farm,movementrestriction,complicatedadministrative proce-dures,compensationlevelequalto70%marketpriceofpig,and gettingcompensationpaymentafter6months.

–Baseline 2: uncertainty of being compensated, destroying dead/unrecovered pigs, movement restriction, complicated administrativeprocedures,compensationlevelequalto70% mar-ket price of pig, and getting compensation payment after 6 months.

–Baseline 3: uncertainty of being compensated, destroying dead/unrecovered pigs, movement restriction, complicated administrativeprocedures,compensationlevelequalto50% mar-ket price of pig, and getting compensation payment after 6 months.

Theprobabilityofchoosingalternativeiwaspredictedfromthe expectedutilityViusingtheformulaasfollows(Gerardetal.,2008):

Pi=1/(1+e−Vi) (2)

TheexpectedutilityViofalternativeiwascalculatedas For-mula(1)usingthepath-worthutilitiesforthedifferentattributes correspondingwithdifferentlevels.

3. Results

3.1. Characteristicsofsamplepopulation

Ofthe240pigholdingscontactedforinterviewing,27people wereunavailableorunwillingtoattendtheinterviewand17people refusedtocompletethechoicesetswhentheinterviewerexplained thescenario.Finally,196respondentswereincludedintheanalysis. Themeanageoftherespondentsinbothprovinceswas48.5 years,rangingfrom28to70years(Table3).Mostrespondentswere male,accountingfor85%ofrespondentsinprovinceAand74%in provinceB.Halftherespondentshadlessthan9yearsof educa-tion,47%reportedhavinggraduatedhighschooland2%statedthey hadanintermediateorcollegedegree.Themajorityofrespondents (80%)hadexperienceinpigproduction,with10yearsormoreof pigraising.Mixedpigholdingsrepresented81%ofsampledfarms (keepingsows,growers,andfatteningpigs),while19%kept fatten-ingpigsonly.Smallpigholdingswith6sowsand100fatteningpigs onaverageweredominantinbothprovinces,rangingfrom79%in ProvinceAto88%inProvinceB.

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Table3

Characteristicsofinterviewedpigfarmers.

Characteristics ProvinceA(n=97) ProvinceB(n=99) Totalsample(n=196)

Gender

Male,n(%) 82(84.5%) 73(73.7%) 155(79.1%)

Female,n(%) 15(15.5%) 26(26.3%) 41(20.9%)

Meanofage(min-max) 48.4(28–61) 48.7(31–70) 48.5(28–70)

Education

Lessthanyear9,n(%) 49(50.5%) 51(51.5%) 100(51.0%)

Highschoolgraduation,n(%) 47(48.5%) 45(45.5%) 92(47.0%)

Intermediate/College,n(%) 1(1.0%) 3(3.0%) 4(2.0%)

Experienceinpigraising(10yearsorover10years),n(%) 79(81.4%) 77(77.8%) 156(79.6%) Productiontype

Mixedfarm,n(%) 65(67.0%) 94(94.9%) 159(81.1%)

Fatteningfarm,n(%) 32(33.0%) 5(5.1%) 37(18.9%)

Productionsize,n(%)

Largefarm(20sowsand/or200fatteningpigs),n(%) 20(20.6%) 12(12.1%) 32(16.3%)

Smallholder(<20sowsand/or200fatteningpigs),n(%) 77(79.4%) 87(87.9%) 164(83.7%)

3.2. Factorsinﬂuencingthefarmer’sdecisiontoreportadisease

event

Utility coefﬁcients, calculated according to the province

(Table4),provestatisticallysignificantinfluencesofallattributes (p<0.01), except for the administrative procedures of disease reporting and compensation payment on farmer’s decision to reportanimal disease.Theattributes’utility coefficients(␤) for “probability ofbeing compensated”and “animalculling policy” arepositive(3.33and2.21,respectively),indicatingthatafarmer wouldbemorelikelytoreportanimaldiseasesincaseofcertainty ofreceivingcompensation,andincaseofacullingpolicyrestricted tonon-recoveringpigsonly.Thehighestvaluesoftheseattributes’ coefficientsindicatethattheyhavethegreatestimpactsonfarmer’s decisiontoreportanimaldiseases.Movementrestrictionhasa neg-ativeimpactonthefarmer’sdecisiontoreport(␤=−0.58,se=0.09). Compensationdeliverytimesof6monthsand1yearobtain neg-ative utilitycoefficients, indicating that delaying compensation paymentreducedtheprobabilityoffarmers’diseasereporting.The utilitycoefficientofcompensationlevelispositiveandsignificant, highercompensationsincreasingthelikelihoodofreporting. 3.3. Willingnesstopay(WTP)forchangingattributelevels

ThehighestWTPoffarmersisobtainedforrestrictingtheculling policytonon-recoveringpigsonlyandforshorteningthe compen-sationdeliverytimefrom1yearto3months,withaveragesofVND 34,100/kgandVND12,300/kg,respectively.Thereisnosignificant differenceintheseWTPbetweenprovinces(Table5).TheWTPfor theabsenceofmovementrestrictions(VND4700–VND13,700/kg) andthereductionofcompensationdeliverytimefrom6monthsto 3months(VND6500toVND8400/kg)aresimilarlydeemed valu-ablechangesbythefarmers.PigproducersinprovinceBarewilling togiveupmoremoneyfortheabsenceofmovementrestriction thanthoseinprovinceA(averageWTPofVND13,700/kgandVND 4700/kg,respectively).However,thisdifferenceisnotstatistically significantduetotheoverlapofconfidenceintervals.

3.4. Probabilityofanimaldiseasereportingbyfarmers

Theprobabilityoffarmerstoreportswinediseasesunder dif-ferentscenariosofcontrolpolicyisrepresentedinFig.1.Under thecurrentsituation(baselinesoftheﬁrstandthesecond scenar-ios)(i.e.uncertaintyofbeingcompensated,movementrestriction, complicatedadministrativeprocedures,compensationlevelequal to70%ofmarketprice,andgettingcompensationpaymentafter6 months),4%(95%CI:0.9%–14.3%)offarmersarewillingtoreport

swinediseasesincaseofcullingallpigsinaffectedfarms,while26% (95%CI:6.2%–65.4%)ofpigholderswouldreportdiseasesintheir farmifonlydead/unrecoveredpigsinaffectedfarmsaredestroyed. Makingadministrativeprocedureslesscumbersome,allowingfree movementsofuninfectedpigsinthearea,andincreasingthe com-pensationpaymentto80%ofmarketvaluedoesnotsigniﬁcantly increasetheproportionoffarmerswillingtoreport(allbetween1 and3%ofreportingprobabilityinscenario1andbetween6and12% inscenario2).Incontrast,iffarmerswerecertainofbeing compen-sated,probabilityofdiseasereportingwouldriseupto52%(incase ofcullingallpigsinaffectedfarms)(95%CI:16.8%–85.3%)andto 91%(95%CI:59.7%–98.5%)(incaseofdestroyingdead/unrecovered pigsinaffectedfarms).

Scenario3,whichtakeslowercompensationlevel(50%market value)intoaccountcomparedtoscenario2,showsan intermedi-ateimprovementinreportingaccordingtothedifferentchangesin policyascomparedtotheﬁrstandsecondscenarios(from16%to 25%reportingandapeakvalueat84%(95%CI:47.9%–96.8%)).

4. Discussion

Thepresentanalysistacklesthequestionofunder-reportingof animaldiseasesin thecase ofVietnamesepigfarmers,focusing ontheimpactofdiseasemanagementpoliciesontheirdecision. Twocomponentsoffarmers’perceptionofthepoliciesarepointed ascrucialtothisdecision:theconfidenceincompensation pay-mentandtheacceptabilityofstampingoutstrategy.Interestingly, thecompensationlevelisshowntohavelessinfluence.Therefore, improvementsindiseasereportingfromanincreaseof compen-sationlevelmaybeoutweighedbydefaultsinthesetwocrucial factors.Onthecontrary,complyingwithfarmers’preferenceson thesetwoaspectsresultsina potentialreportingprobabilityof 80%–90%.Similarlytocompensationlevel,movementrestriction anddeliverytimeofcompensationareminoralthoughsignificant decisionfactors.Theadministrativeproceduresfordisease report-ingdonotappearasanimportantfactor.

Themethodologicalchoiceofexpressingcompensationsasa priceperkgpigwasaimedatmakingthechoicemorerealistic andacceptableforfarmers.Therefore, attentionwaspaidtothe numberofpigsinthesamplingprocedureandseparateanalyses wereperformedforsmallholdersandlargerfarms,despitethelow numberoffarmersinthelattercategory(duetothelowfrequency ofthisfarmtypeinthestudyregions).Theveryclosecoefﬁcient estimatesbetweenthetwo groupsindicatethatthechoicesets werewellunderstoodbyintervieweeswithsimilarstakesinthe decision-makingbeingrevealed.Giventhissimilarityin

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decision-Table4

Utilitycoefﬁcientestimatesforfactorsinﬂuencingthefarmers’decisiontoreport.

Attribute Coefﬁcient(95%CI)

ProvinceA(n=97) ProvinceB(n=99) Totalsample(n=196)

Probabilityofbeing compensated Uncertaintyvs.Certainty 4.70*** (4.26;5.14) 2.56*** (2.30;2.81) 3.33*** (3.11;3.54) Cullingpigs

Allpigsatfarmvs.

Unrecoveredpigs 2.94*** (2.52;3.35) 1.89*** (1.63;2.16) 2.21*** (2.0;2.43) Administrativeprocedures Complicatedvs.Simple 0.001 (0.31;0.31) 0.13 (−0.11;0.37) 0.10 (−0.09;0.29) Movementcontrol Nomovementbanvs. Movementban −0.42*** (−0.69;−0.15) −0.70*** (−0.91;−0.46) −0.58*** (−0.75;−0.42)

Deliverytimeofcompensation

payment 6months 1year −0.57*** (−0.90;−0.24) −0.81*** (−1.14;−0.48) −0.42*** (−0.67;−0.17) −0.82*** (−1.07;−0.56) −0.44*** (−0.64;−0.25) −0.80*** (−1.0;−0.6)

Compensationlevels(per103

VND/kg) 0.09*** (0.06;0.11) 0.05*** (0.03;0.07) 0.06*** (0.05;0.08) Numberofrespondents 97 99 196 Numberofobservations 3492 3564 7056

Loglikelihoodofthemodel −600.82 −905.28 −1557.87

Loglikelihoodofthemodel

withoutpredictors

−1278.79 −1305.15 −2583.94

McFaden’spseudoR2 _0.53 _0.31 _0.40

CI:ConﬁdenceInterval.

***_{statistically}_signiﬁcant_(p_<_0.01).

Table5

Farmers’willingnesstopayforchangesofattributelevels.

Attribute WTPforchangeinattributes(103_VND/kg_of_culling_pig)_Mean_(95%_CI)

ProvinceA(n=97) ProvinceB(n=99) Totalsample(n=196)

Cullingpigsrestrictedto unrecoveredpigs 33.4 (25.7,46.2) 38.0 (27.2,60.8) 34.1 (27.7,43.8) Nomovementban 4.7 (1.7,8.7) 13.7 (8.0,24.0) 9.0 (6.0,13.0) Deliverytimeofcompensation

changedfrom6monthsto3 months 6.5 (2.5,12.0) 8.4 (3.0,17.1) 6.8 (3.6,11.1) Deliverytimeofcompensation

changedfrom1yearto3 months 9.2 (5.3,14.7) 16.3 (10.0,27.6) 12.3 (8.7,17.1) CI:ConﬁdenceInterval.

making,theanalysisofreportingprobabilitiesispresentedherefor

thewholesample.

TheWTPhighlightsthetruebarrierthatanimalcullingpolicy

posesonsurveillanceefﬁcacy.Indeed,farmers wouldbewilling

topay43%–80% market value ofpig tobesurethat only

non-recoveringpigsaredestroyed.Classicalstamping-outpolicywould

leadfarmerstohidediseases,despitecompensationlevelsashigh

as80%marketvalueofpigaswellasthecertaintyofreceivingthis

money.Themotivesbehindtheseresultswereobtainedthrough

openqualitativeinterviewsafterDCEcompletion.First,notiﬁable

swinediseases suchasPRRSand FMDareendemic inVietnam

andthereforefarmersperceiveapolicyofstamping-outaslacking

relevanceastheyareusedtomanagingthesediseaseslikeother

endemicproductiondiseases.Mostfarmersbelieveinahigh

prob-abilityofsuccessfultreatmentandabetterproﬁttobeexpected

fromrecoveredpigsthanfromcompensationpayment.

Compen-sationlevelat80%marketvalueofpigwasconsideredascovering

breedingcostsandapartoffeedingcosts.Farmerestimatesthe

successrateoftreatmentsat50%,hencea50%chanceof

gener-atingproﬁt.Second,thefarmersexpecta riseinpigpricesafter

diseaseoutbreaks,creatinga particularspeculativeopportunity.

Third,thedestructionofclinicallyhealthypigsisconsidered

unac-ceptable,beingperceivedasawasteofresources,food,andvaluable

geneticasset.Indeed,thecullingofclinicallyhealthybreedingstock

isunacceptableduetothehighvalueofsowswithgood

perfor-mance(i.e.annualnumberofpigletsandpigletweightatweaning,

maternalbehavior).MostfarmersbelievethatPRRShasnoeffecton

thereproductiveperformanceofsows.Thereforetheywouldnot

acceptthecullingofasymptomaticsowsevenafterconﬁrmation

ofinfection.

Compensationisconsideredasacriticalelementofeffective

diseasecontrolas itencourages farmers’reportingand

compli-ancewiththecullingofconﬁrmedorsuspectedcasesofinfection,

thusreducingtheriskofdiseasespreading(WorldBank,2006).

Compensationrateshouldbenolessthan50%ofmarketvaluefor healthyanimalsandrecommendedratesrangefrom75to90%of thereferenceprice(WorldBank,2006).Lowercompensationcould beappliedfordeadanimalsthanfordiseasedorhealthyanimals toencourage earlyreporting(World Bank, 2006).In agreement withtheveterinaryregulationsofVietnam,thesame compensa-tionlevelwasproposedinourstudyforallcategoriesofdestroyed pigs(piglets,fatteners,growers,sows,andboar,deadorsickpigs) (MOF,2008).Thislackofacknowledgementofthehighervalueof breedingstockappearsasamajordisincentivefordisease report-ing.Inthecontextoftheavianinﬂuenzacompensationschemein Indonesia,contingentvaluationwasusedtoquantifysucha

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dif-Fig.1.Probabilityofswinediseasereportingbyfarmersunderdifferentscenariosofcontrolpolicy.

ferentiatedwillingnesstoacceptcompensationfordifferenttypes ofbirds(Yakhshilikovetal.,2009).However,ourstudywasnot designedtoestimatethepotentialimprovementobtainedthrough a differentiated compensationschemeand this question would thusrequireaspeciﬁcapproach.

The uncertainty and lack of transparency of procedures for cullingand compensation paymentappear hereas barriers for diseasereporting.AccordingtoVietnamesediseasecontrolpolicy (MARD,2008,2007),cullingpigsatfarmsafterconﬁrmationof dis-easecanapplyforallpigsincaseofanewoutbreakoriftheoutbreak occursinalimitedarea(fewhouseholdsinthevillage/commune) toruleoutdiseaseearlier.Cullingofsolelynon-recoveringpigsis appliediftheoutbreakcoversalargeareaoranareawherethe dis-easehasoccurredseveraltimes.Thisﬂexibilityofproceduremakes thingsunclearforfarmers.Theseresultssuggesttheimportanceof clarifyingcullingruleswithadequatecommunicationstrategy.

Findingsofthestudyalsoemphasizethewideracceptabilityof restrictedcullingandtheinteresttoapplythisstrategyina max-imumofrelevantcases.Theeffectivenessofsuchtargetedculling onPRRS,FMD,and CSFdiseasecontrolinVietnamwould prob-ablybeverylimited butsimilartothecurrent situationofhigh levelofunder-reportingandlocaldiseasemanagementstrategy. Howeveritwouldgreatlyimprovethesensitivityofthecurrent surveillancesystemsprovidesbetterepidemiologicalinformation onﬁeld diseasesituationand help rebuilding farmers’trust on nationalsurveillance and control policies.On thelong run this wouldprovidestrongerbasisfordeﬁningnovelcontrolstrategies incollaborationwithfarmersandlocalstakeholders.

Eventhoughtheadministrativeproceduresdonotshowhere asignificantinfluenceonfarmers’willingnesstoreport(p>0.05), itisexpectedthatsimplifiedandtransparentprocedureswould promoteclarityofthesystemandfarmers’trust,whicharefactors showingasignificanteffectonreporting.Adistrustinveterinary authoritiesandcontrolmeasuresis,indeed,listedasanimportant barriertodiseasereporting(Bronneretal.,2014;Elbersetal.,2010; Palmeretal.,2009).Hereagain,thetimelinessandreliabilityof compensationdeliveryinterveneascriticalelementsinbuilding trustbetweenfarmersandofficials(WorldBank,2006).

InopeninterviewsfollowingtheDCE questionnaire,farmers furtherjustiﬁedmovementrestrictionasanobstacletoreporting bytheextensionofpigkeepingtimeandincreaseofinputcost. Thesethenindicatedawillingnesstopayforlaboratorytestsincase ofoutbreakintheirregiontomaintaintherighttofreemovement. Thiswillingnessmightalsobefurtherexploredthoughcontingent valuationandtheinstitutionalfeasibilityofsuchanarrangement wouldthenneedtobeassessed.Continuityofbusinessisa par-ticularmodalityoffootandmouthdiseaseresponseintheUnited States,tobeappliedincombinationwithquarantineand move-mentcontrol (USDA, 2015).It allows non-affectedfarmstosell non-infectedanimalsornon-contaminatedanimalproductsoutof thecontrolarea.Thisisasolutiontomaintainagriculturalbusiness operationswhilealsomitigatetheriskofdiseasespread.However, itrequiresnotonlysamplingandtestinganimalsbutalsoassessing farm’sbio-securitybeforemovement(USDA,2015).

FewstudieshaveappliedDCEinVietnaminthedomainof ani-malscience(Costalesetal.,2008;Roessleretal.,2008;Zhangetal., 2014)anditsuseinanimalhealthsurveillanceisevenmore

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lim-ited.DCEprovidesquantitativeevidenceoftherelativeimportance offactorsinfluencingindividualdecision-making,andclarifiesthe trade-offsbetweengivenattributes,thuspredictingtheprobability ofuptakeinspecifiedalternatives(WHO,2012).AlthoughDCEis basedonhypotheticalchoiceratherthanactualchoice,theresults ofstudiesontheenvironment(Adamowiczetal.,1994)and pub-lichealth(Lambooijetal.,2015)haveindicatedtheconsistency ofstatedandrevealedpreferences.Toourknowledge,thereisno studycomparingtheresultsofstatedandrevealedpreferenceson animalhealthsurveillance.Theunobservablenatureofthechoice ofnotreportingdiseasesmakesitdifficulttoconsiderprotocols abletomakesuchacomparison.DCEallowsforthisestimationby theinclusionofanopt-outalternativerepresentingnon-reporting behaviorinthechoiceset.Thereforethis methodologicalchoice revealscrucialtoapplyDCEtosurveillanceevaluationinVietnam, whereunderreportingofanimaldiseaseisanimportantfeature.

5. Conclusion

DCEprovedfruitfulintheanalysisofreportingthebehaviorof pigfarmersinVietnam.Moreparticularly,ithighlightsthe impor-tanceofgeneralortargetedcullingstrategy.Thequantiﬁcationof expectedimprovementsofreportingprobabilitymaybeusedto modeltheexpectedbeneﬁtsofinstitutionalchangesinsurveillance policyinVietnam.

Acknowledgements

ThisstudywascarriedoutintheframeworkoftheCIRAD- REVA-SIAproject,theCIRADandIRDjointyoungresearcherteamproject JEAI-SWEIDandwiththesupportofGREASEnetwork.Wethank theveterinariansofthesubdepartmentofanimalhealthand vet-erinarystations,andthelocalauthoritiesinthestudyareafortheir supportindatacollectionandallinterviewedpigholdersfortheir timeandparticipationinthisstudy.

AppendixA. Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound,in theonlineversion,athttp://dx.doi.org/10.1016/j.prevetmed.2017. 01.002.

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