Download Trial examen NEM-20806 2016 - Di-Et-Tri

Example-examBasicsofInfectiousDiseases(NEM-20806)2015/16:
Question1:The‘diseasetriangle’isaconceptualmodelusedtobetter
understandtheepidemiologicaldynamicsofinfectiousdiseases.
A. Whatarethethreefactorsthatmakethecornersofthedisease
triangle?
[ANSWER(2points):environment,infectiousagent,andhost]
B. Howcanthediseasetrianglehelptounderstandasuddenoutbreak
ofaninfectiousdisease?
[ANSWER(4points):theepidemiologicaloutcomeofaninfectiousdisease
isdeterminedbyinteractionsbetweenenvironment,pathogen,andhost.
Suddenoutbreaksofinfectiousdiseasesalwaysinvolveachangeeitherin
theenvironment,inthepathogen,orinthehost.Changesinthe
environmentmayforinstanceenablethetransmissionofpathogenfroma
novelsource(e.g.reservoirhostinjungle).Specificgeneticchangesin
pathogensmayincreasetheirvirulence(e.g.mutationsinvirussurface
proteins).Changesinhostbehaviourmayenhancethetransmissionofthe
causalagent.Forexample,thecurrentaggregationofthousandsofpeople
inrefugeecampsindroughtstrickenEastAfricagreatlyenhancesthe
likelihoodoftransmissionofinfectiousdiseases.]
C. Applythediseasetriangletoexplainarecentpandemicofan
infectiousdisease.
[ANSWER(2points):theswinefluepidemicisthoughttohaveoccurred
afterageneticrecombinationintheviralgenomeofaninfluenzavirus
(pathogenfactor).People(hostfactor)lackedimmunitytothisnewhighly
virulentvirus,whileinternationaltravelling(environmentalfactor)of
carriersofthevirusallowedforarapidspreadofthediseasethroughout
theglobalcommunity.]
Question2:
Mostpeoplegetmicrobialinfectionswhentheirimmunesystemsare
weakened.Nevertheless,alsopeoplehavinganormalfunctioningimmune
systemcangetinfectedbypathogenicbacteria.
A. Explainhowbacteriacancausediseasedespitethepresenceofa
functioningimmunesystem(2points)
B. Giveexamplesofimmuneevasionmechanism(atleast3)
(4points)
C. Explainwhythedevelopmentofantibioticresistanceisaproblemin
healthcare(4points)
Thisquestionhasbeendiscussedinthelecture.Seeforanswerslectureslides.
Question3:
Despitetheoccurrenceofmanyfungalspecies,fungiarenotknownas
majorhumanpathogens.
A. Explainwhyfungigenerallydonotcauseseverediseasesonhumans
andanimals.(4points)
B. Oncesufferingfromasystemicmycosis,mortalityisgenerallyvery
high.Explainwhyitisdifficulttodevelopantifungaldrugs.(3
points)
C. Systemicmycosescanbedividedintotrueandopportunistic
systemicmycoses.Howmanyfungalspeciescancausetruesystemic
mycosesandhowmanyfungalspeciescancauseopportunistic
systemicmycoses?(3points)
Thisquestionhasbeendiscussedinthelecture.Seeforanswersthelecture
slides.
Question4:
A. Whatisthedifferencebetweenadirectlytransmittedandan
indirectlytransmittedpathogen?(Usediagramstoillustrateyour
answer;4points)
[ANSWERS:Adirectlytransmittedprotozoanpassesfromonehosttoanother
withouttheneedforavector.Directtransmissionmaybethroughamedium
suchassoilorwater.
Anindirectlytransmittedprotozoanparasitehasatransmissioncyclewhich
involvesavector.Theprotozoanistransmittedfromonehosttoanotherviaa
vectorwhichmaybeaninsect.]
B. Givetwoexamplesofdirectlytransmittedprotozoanpathogens (2
points)
[ANSWERS:Directlytransmitted:Examplesinclude,Giardiasis(Giardia
duodenalisandGiardialamblia),Toxoplasmosis(Toxoplasmagondii)]
C. Givetwoexamplesofindirectlytransmittedprotozoanpathogens(2
points)
[ANSWERS:Indirectlytransmitted(vectorborne):Examplesinclude,Chagas
disease(Trypanosomacruzi),Africantrypanosomiasis(Trypanosomabruceispp),
Leishmaniasis(Leishmaniaspp),Malaria(Plasmodiumspp).]
D. Whataresomeofthechallengesinvolvedinthecontrolofprotozoan
pathogens?2points
[ANSWERS:Antigenicvariation,evasionofhostimmunesystem,natural
reservoirsofinfection,vectorsbecomeresistanttoinsecticidesusedtocontrol
them,parasitesbecomeresistanttothedrugsusedtotreatinfection.]
Question5.
A. List three ways in which arthropods may be of public health
importancetohumansandgiveoneexampleforeach.(6points)
[ANSWERS:Nuisancebiting(e.g.headlice,mosquitobites,midges);Allergiesto
biteorsting(e.g.bee,wasp,ant,mosquito);Diseasecausingagent(e.g.Myiasis
bythehumanbotfly,Dermatobiahominis);Diseasevector(e.g.mosquitoes
transmittingmalaria,tickstransmittinglymedisease).]
B. WhatisthecausativeagentofLymediseaseandhowisthisdisease
transmitted?(2points)
[ANSWERS:Causativeagent=Borreliabacteria.Transmittedfromonehostto
anotherthroughbitesofinfectedticks(thesheeptickIxodesricinus).]
C. HowcaninfectionwithLymediseasebeprevented? (2points)
[ANSWERS:Tickchecks-removetickwithin24hoursofattachment;Useof
DEET-containingrepellentstopreventtickbites.]
Question6
Acysteineproteaseinhibitorfromthemurineparasitichelminth
Heligmosomoidespolygyrus(Hp-CPI)isabletomodulatedendriticcell
functionandsubsequentresponsesoftheadaptiveimmunesystem.
A. Describestep-by-stephowforeigncompounds(e.g.PAMP’sor
antigens)arebeingperceivedbydendriticcellsandultimatelylead
toThelpercellactivation?[2points]
[Answers:PerceptionbyPRR’s,endocytosis,fusionwithlysosomes,loadingonto
MHC-IImolecules,antigenpresentationandTcellactivation.]
Inthefigurebelowyoucanfindtheeffectofrecombinant(r)Hp-CPIon
mousebonemarrow-deriveddendriticcells,whicharestimulatedwith
ligandsforTLR4(LPS)andTLR9(CpG).
CD40
CD80
CD86
MHC-II
MFI:meanfluorescentintensity(ameasureforexpressionlevel)
B. PolarisationofTcellsdependsonthreedistinctsignalsgivenby
antigenpresentingcells.Whichofthesethreesignalsareaffectedby
Hp-CPIasstatedinthefigure?[2points]
[Answers:Signal1–antigenpresentation;Signal2–co-stimulation;Signal3–
cytokines]
C. KnowingtheeffectthatHp-CPIhasondendriticcells,whichtypeofT
helpercellresponsewillyouexpect?Furthermore,whatdoyou
expecttobetheeffectonthetypeofantibodiesthatwillbeproduced
byB-cells?[3points]
[Answers:ReductionofIL-12=>suppressionofTh1responses;ReductionofIL6=>suppressionofTh17responses,favoringTregs;Th2dominatedimmune
responsesaretheresult;Th2typeimmunitywillfavortheproductionof
IgE/IgG4byBcells]
D. BesidestheimmunomodulatorypropertiesillustratedaboveforHpCPI,helminthsemploymultipleothermechanismstomodulatehost
immuneresponses.Giveatleast3otherexamples.[3points]
[Answers:Proteases,proteaseinhibitors,chemokineblockersandanti-oxidants
toinhibiteosinophilrecruitmentandeffectorfunctions;antibodyclassswitching
fromIgEtoIgG4tolimiteosinophildegranulation;alternativeactivationof
macrophagestoblockTh1responsesandinducewoundhealing;promoting
regulatoryTcelldevelopment;promotinglymphocytehyporesponsiveness
(anergy),cytokinemimics(e.g.TGF-b1),etc….]
Question7:
Helminthparasiteshaveanumberofcharacteristicfeaturesthatmakes
themdifferentfromothercausalagentsofinfectiousdiseases.
A. Helminthparasitescannotoutpacetheimmunesystemofthehost.
Explainwhy.
[ANSWER(4points):Helminthsdonotreplicateinsideasinglehost
individual.Theparasiteloadofanindividualresultsfrommultiple
infectionswithparasites/eggs.Unlikevirusesandbacteria,replicationof
helminthparasitesisnotfasterthannormalresponsetimeoftheimmune
systemofthehost.]
B. Givetwoothercharacteristicfeaturesofhelminthparasites.
[ANSWER(onepointeach):
Persistenceofindividualparasites(severalyears),andthelowmortality
ratesassociatedwithparasiticdiseasesinthehost]
C. Somehelminthparasitescangointoadevelopmentalarrest.Give
tworeasonswhyadevelopmentalarrestcanbebeneficialfora
parasite.
[ANSWER(2pointsforeachgoodanswer):
Developmentalarresthelpstheparasitestosurviveadverseconditionsin
absenceofahost(i.e.eggsofAscarissurvive>10years),and
developmentalarrestisusedasameansfordemographiccontrolto
preventthatthebuildupofparasiteinfectionsinahostpopulation
becomesohighthatitincreasesthemortality.Realizethathelminth
parasitesareobligateparasitesthatwanttopersistforalongtimein
livinghost.Earlydeathofahostisnotastablestrategyfortheparasite.]
Question8:
A. DrawtheProductionFunctionforlivestockproductionandshowthe
impactofdiseaseonthisFunction(2points).
B. Mentionatleast2differencesbetweenproductiondiseasesand
HighlyContagiousLivestockDiseases(HCLD;2points).
[ANSWERS:Cause:diseaseagent<>lossoffreestatus
Impacts:decreasedproduction(efficiency)<>measurestocontrolthe
disease
Aim:mitigation<>regainfreestatusasap]
C. Mentionthefourcategoriesofmonetarycoststhatcanbecausedby
anoutbreakofaHighlyContagiousLivestockDisease(HCLD;2
points).
[ANSWERS:DirectCosts(DC);DirectConsequentialCosts(DCC);Indirect
ConsequentialCosts(ICC);AftermathCosts(AC)]
D. BesidesthemonetaryimpactsdiscussedinLecture1,variousother
factorscanaffecttheimpactofaHighlyContagiousLivestock
Disease(HCLD);mentionatleastthreeofsuchfactors(2points).
[ANSWERS:Zoonoticnatureofthedisease;Hobby/Non-commercial
farmers;Productionstructure;Regionwherethediseaseoccurs;Control
strategyapplied]
E. IfyoucompareFoot-and-MouthDisease(FMD)andHighly
PathogenicAvianInfluenza(HPAI),whatisthemostimportant
differencewithregardtoimpactonsociety?(1point)
[ANSWER:ZoonoticnatureofHPAI]
F. Hastheaboveanswereddifferencethesameimportanceinall
countriesallovertheworld?Providetogetherwithyouranswera
shortexplanationoranillustration.(1point)
[ANSWER:No;seeHPAIinSE-Asia:muchmorefearforhumanhealth,
thereforeuseofvaccin;plus:infrastructureforcontrolisquitedifferent,
thereforemeasuresatvillagelevel.]
Question9:
KuruwasadeadlypriondiseaseinPapuaNewGuinea.
A. HowwasKurudiseasetransmittedbetweenmembersoftheForay
tribe?(1point)
[ANSWER:Viaritualisticcannibalism.]
B. WhyweremorefemalesinfectedwithKuruthanmen?(1point)
(ANSWER:Moreintensiveroleforwomenintherituals.]
C. Name2changesintissuesofthebrainthatcharacterizeprion
diseases.(2points)
[ANSWER:1.vacuoles/spongiformtissues;2.amyloidplaques/protein
deposits/prionfibrils]
D. SpellouttheabbreviationsPrPc,PrPsc,PrPsen,PrPres.(2points)
[ANSWER:Prionprotein-cellular,scrapie,sensitive,resistant]
E. Dr.CharlesWeismannperformedcrucialanimalexperimentsto
showspecificityintheinductionofpriondisease(scrapieinmice).
Whichmousedevelopsseverediseasewhenchallenged(“infected”)
withhamsterscrapie:transgenicmiceexpressing5-10timesmore
prionsortransgenicmiceexpressinghamsterprions?Explainyour
answer.(4points).
[ANSWER:Transgenicmiceexpressinghamsterprions,onlythesemiceare
susceptibletothedisease.Miceexpressingmouseprionsdonotdevelopdisease
uponchallengewithhamsterscrapie.]