Parasitology an Introduction

8/7/2019 Parasitology an Introduction

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What is a parasiteWhat is a parasite

a pathogen thata pathogen thatsimultaneously injures andsimultaneously injures and

derives sustenance from itsderives sustenance from itshosthost

Some organisms calledSome organisms calledparasites are actuallyparasites are actually

commensalscommensals

neither benefitneither benefitnor harm their hostnor harm their host

for example,for example, Entamoeba coliEntamoeba coli

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ParasitologyParasitology area of biology concerned with thearea of biology concerned with the

phenomenon of dependence of onephenomenon of dependence of oneliving organism on anotherliving organism on another

Medical ParasitologyMedical Parasitology

Concerned primarily with the animalConcerned primarily with the animalparasites of humans and theirparasites of humans and theirmedical significance, as well as theirmedical significance, as well as theirimportance in human communitiesimportance in human communities QuickTime and aTIFF (Uncompressed) decare needed to see this pi



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Biological RelationshipsBiological Relationships

SymbiosisSymbiosis:: is the living together of unlike organismsis the living together of unlike organisms

may also involve protection or other advantagesmay also involve protection or other advantages

to one or both partnersto one or both partners

Different forms of symbiosis: distinguishedDifferent forms of symbiosis: distinguishedon whether or not the association ison whether or not the association isdetrimental to one of the 2 partners.detrimental to one of the 2 partners.

CommensalismCommensalism

MutualismMutualism

ParasitismParasitism


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CommensalismCommensalism

Is a symbiotic relationship in which 2Is a symbiotic relationship in which 2species live together and one speciesspecies live together and one species

benefits from the relationship withoutbenefits from the relationship withoutharming or benefiting the otherharming or benefiting the other

e.g.e.g. Entamoeba coliEntamoeba coli in the intestinal lumenin the intestinal lumenis supplied with nourishment and isis supplied with nourishment and isprotected from harm, while it does notprotected from harm, while it does notcause any damage to the tissues of its host.cause any damage to the tissues of its host.


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MutualismMutualism

Is a symbiosis in which 2 organismsIs a symbiosis in which 2 organismsmutually benefit from each othermutually benefit from each other

e.g. termites and the flagellates ine.g. termites and the flagellates intheir digestive system, whichtheir digestive system, which

synthesize cellulase to aid in thesynthesize cellulase to aid in thebreakdown of ingested woodbreakdown of ingested wood


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ParasitismParasitism

A symbiotic relationship where oneA symbiotic relationship where oneorganism, the parasite, lives in ororganism, the parasite, lives in or

another (the host), depending on theanother (the host), depending on thelatter for its survival and usually at thelatter for its survival and usually at theexpense of the hostexpense of the host

e.g.e.g. Entamoeba histolyticaEntamoeba histolyticaderivesderivesnutrition from the human host andnutrition from the human host andcauses amebic dysenterycauses amebic dysentery


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Parasites:Parasites:describedaccordingtotheirhabitatormodeofdescribedaccordingtotheirhabitatormodeofdevelopmentdevelopment

EndoparasiteEndoparasite::a parasite livinga parasite living

inside the body of a hostinside the body of a host

EctoparasiteEctoparasite: a parasite living: a parasite living

outside the body of a hostoutside the body of a host

Aparasite is consideredAparasite is considered erraticerratic when it is foundwhen it is found

in an organ which is not its usual habitatin an organ which is not its usual habitat


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EndoparasiteEndoparasite

PresenceofanendoparasiteinaPresenceofanendoparasiteinahostiscalledanhostiscalledaninfectioninfection

Qui iI ( r ) r r

r t t i i tur .

Qui iI ( r ) r r

r t t i i tur .


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presenceofanpresenceofanectoparasiteectoparasiteinsidethehostisinsidethehostiscalledancalledan

infestationinfestation



EctoparasiteEctoparasite


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Erratic ascarisErratic ascaris

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ParasitesParasites

Obligate parasitesObligate parasites: need a host at some: need a host at somestage of their life cycle to completestage of their life cycle to completetheir development and to propagatetheir development and to propagatetheir speciestheir species e.g. tapeworms depend entirely upon theire.g. tapeworms depend entirely upon their

host for existencehost for existence

Facultative parasiteFacultative parasite: may exist in a free: may exist in a free--living state or may become parasiticliving state or may become parasiticwhen the need ariseswhen the need arises


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Accidental or Incidental parasiteAccidental or Incidental parasite: establishes: establishes

itself in a host where it does not ordinarily liveitself in a host where it does not ordinarily live

Permanent parasitePermanent parasite: remains on or in the body: remains on or in the bodyof the host for its entire life cycleof the host for its entire life cycle

Temporary parasiteTemporary parasite: lives on the host only for: lives on the host only fora short perioda short period

Spurious parasiteSpurious parasite: a free: a free--living organism thatliving organism thatpasses through the digestive tract withoutpasses through the digestive tract withoutinfecting the hostinfecting the host


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HostHost::classifiedbasedontheirroleinthelifecycleoftheparasite

Definitive or final hostDefinitive or final host: is one in which the: is one in which theparasite attains sexual maturityparasite attains sexual maturity

Humans are the definitive host in taeniasisHumans are the definitive host in taeniasis

Intermediate hostIntermediate host: harbors the asexual or: harbors the asexual or

larval stage of the parasitelarval stage of the parasite Pigs or cattle as intermediate hosts ofPigs or cattle as intermediate hosts of TaeniaTaenia

spp.spp. whilewhile ssnails are hosts ofnails are hosts of Schistosoma sppSchistosoma spp..


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Paratenic hostParatenic host: one in which the parasite: one in which the parasitedoes not develop further to later stages.does not develop further to later stages.However, the parasite remains alive andHowever, the parasite remains alive andis able to infect another susceptible hostis able to infect another susceptible host

Paragonimus metacercariae in raw wild boarParagonimus metacercariae in raw wild boarmeat can pass through the intestinal wall ofmeat can pass through the intestinal wall of

humans and complete its developmenthumans and complete its development


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Reservoir hostsReservoir hosts: allow the parasites life cycle: allow the parasites life cycle

to continue and become additional sources ofto continue and become additional sources ofhuman infectionhuman infection Pigs are reservoirs ofPigs are reservoirs of Balantidium coliBalantidium coli

Field rats ofField rats ofParagonimus westermaniParagonimus westermani

Cats ofCats of Brugia malayiBrugia malayi

Humans are not always the final hostHumans are not always the final host

Man may be the most important host in theMan may be the most important host in thespread of the disease or an incidental host ofspread of the disease or an incidental host ofparasites prevalent in other animalsparasites prevalent in other animals


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Vectors:Vectors:Responsiblefortransmittingtheparasitefromonehosttoanother

Biologic vector:transmitstheparasiteonlyafterthelatterhascompleteditsdevelopment withinthehost

Mechanical or phoretic vector:

transportstheparasite


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Biologicvector: Aedes sucksbloodfromapatient withfilariasis, theparasiteundergoes several stagesofdevelopmentfromthefirststagelarvato 3rdstagelarva

beforeitistransmittedtoanother susceptiblehost

Mechanical or phoretic vector:

Flies and cockroaches that feedon fecal material may carryenteric organisms and transferthese to food


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Exposure and InfectionExposure and Infection CarrierCarrier: harbors a pathogen without manifesting any signs: harbors a pathogen without manifesting any signs

and symptomsand symptoms

ExposureExposure: process of inoculating an infective agent: process of inoculating an infective agent

InfectionInfection: connotes the establishment of the infecting: connotes the establishment of the infectingagent in the hostagent in the host

Incubation periodIncubation period (clinical incubation period): period(clinical incubation period): period

between infection and evidence of symptomsbetween infection and evidence of symptoms

PrePre--patent periodpatent period (biologic incubation period): period(biologic incubation period): periodbetween infection or acquisition of the parasite andbetween infection or acquisition of the parasite andevidence or demonstration of infectionevidence or demonstration of infection


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AutoinfectionAutoinfection::

whenaninfectedindividualbecomeshisowndirectwhenaninfectedindividualbecomeshisowndirectsourceofinfectionsourceofinfection

E.g.Enterobiasis: InfectiveeggsendupinthehandsE.g.Enterobiasis: Infectiveeggsendupinthehandsbyscratchingtheperianalareas wherethegravidbyscratchingtheperianalareas wherethegravidfemaleslaytheireggsfemaleslaytheireggs

Superinfection or HyperinfectionSuperinfection or Hyperinfection:: whenthealreadyinfectedindividualisfurtherwhenthealreadyinfectedindividualisfurther

infect

ed with

th

esamespeciesleadingt

omassiveinfect

ed with

th

esamespeciesleadingt

omassiveinfectioninfection

AlterationinthenormallifecycleofAlterationinthenormallifecycleof StrongyloidesStrongyloidesresultsinalargeincreasein wormburdenresultsinalargeincreasein wormburden severeseveredebilitation/deathdebilitation/death


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Sources of InfectionSources of Infection

1.1. Contaminated soil and waterContaminated soil and water: most: mostcommoncommon

Lackofsanitarytoilets & useofhumanLackofsanitarytoilets & useofhumanexcretaasfertilizerexcretaasfertilizer favorinfection withfavorinfection withascaris, hookwormascaris, hookworm

Watercontaminated withcystsofamebaeWatercontaminated withcystsofamebaeorflagellatesas wellascercariaeoforflagellatesas wellascercariaeofSchistosomaSchistosoma

2.2. FoodFood::maycontaintheinfectivemaycontaintheinfective

stageoftheparasitestageoftheparasite

3.3. ArthropodsArthropods::e.g.mosquitoesase.g.mosquitoesasvectorsofmalariaandfilariaparasitesvectorsofmalariaandfilariaparasites


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4.4. other animalsother animals (wild or domesticated) may harbor the(wild or domesticated) may harbor theparasiteparasite

E.g.catsaredirectsourcesof ToxoplasmaifnectionE.g.catsaredirectsourcesof Toxoplasmaifnection

5.5. other sourcesother sources Anotherperson, hisbeddingsandclothing, theimmediateAnotherperson, hisbeddingsandclothing, theimmediate

environmenthehascontaminatedenvironmenthehascontaminated E.g.asymptomaticcarriersofE.g.asymptomaticcarriersofEntamoebahistolyticaEntamoebahistolytica workingasworkingas

foodhandlersfoodhandlers

AutoinfectionAutoinfection -- wheretheselfisthesourceofinfectionasseeninwheretheselfisthesourceofinfectionasseenin

thelifecyclesofthelifecyclesofE.vermicularis, HymenolepisnanaandE.vermicularis, HymenolepisnanaandStrongyloidesstercoralisStrongyloidesstercoralis


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AutoinfectioninStrongyloidesAutoinfectioninStrongyloides RhabditiformlarvaeinlargeintestineRhabditiformlarvaeinlargeintestine filariformlarvaefilariformlarvae penetratepenetrate

intestinalmucosaintestinalmucosa follow thenormalinfectivecyclefollow thenormalinfectivecycle


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Modes of TransmissionModes of Transmission

MouthMouth is the most likely portal of entryis the most likely portal of entry Mostcestodes, trematodesandprotozoansarefoodborneMostcestodes, trematodesandprotozoansarefoodborne

Skin penetrationSkin penetration::e.g.hookworms &e.g.hookworms & StrongyloidesStrongyloides

Arthropods:Arthropods: asvectorstransmitparasitesthroughbitesasvectorstransmitparasitesthroughbites Agentsof malaria, filaria, leishmaniasisandtrypanosomiasisAgentsof malaria, filaria, leishmaniasisandtrypanosomiasis

Congenital transmissionCongenital transmission::Toxoplasma gondiiToxoplasma gondiitrophozoitestrophozoitescancrossthe placentacancrossthe placenta Intransmammary infection withIntransmammary infection with Ancylostoma and StrongyloidesAncylostoma and Strongyloides,,

the parasites maybetransmittedthroughthe mothers milkthe parasites maybetransmittedthroughthe mothers milk


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Modes of TransmissionModes of Transmission

Other waysOther ways

InhalationInhalation of airof air--borne eggs ofborne eggs ofEnterobiusEnterobius

Sexual intercourseSexual intercourse asinthecaseofasinthecaseofTrichomonas vaginalisTrichomonas vaginalis


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NomenclatureNomenclature Animal parasites are classified according to theAnimal parasites are classified according to theInternational Code of Zoological NomenclatureInternational Code of Zoological Nomenclature

Each phylum is subdivided into classes which are furtherEach phylum is subdivided into classes which are further

subdivided into orders, families, genera and speciessubdivided into orders, families, genera and species Further subdivisions of suborder, superfamily and subspecies areFurther subdivisions of suborder, superfamily and subspecies are

employed at timesemployed at times

Family names are formed by addingFamily names are formed by adding ~idae~idae to the stem ofto the stem of

the genus typethe genus type

Names of the genera and species are italicized orNames of the genera and species are italicized orunderlined when writtenunderlined when written


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Life CycleLife Cycle

May be simple or complicatedMay be simple or complicated

As the life cycle becomes moreAs the life cycle becomes morecomplicated, the lesser the chances arecomplicated, the lesser the chances arefor the individual parasite to survivefor the individual parasite to survive

Perpetuation of a species of parasitePerpetuation of a species of parasitedepends upon its ability to ensuredepends upon its ability to ensuretransmission from one host to the nexttransmission from one host to the next


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Epidemiologic measures

Cumulative prevalenceCumulative prevalence:: percentageofindividualsinapopulationinfected withpercentageofindividualsinapopulationinfected withatleastoneparasiteatleastoneparasite

Intensity of infectionIntensity of infection::

numberof wormsperinfectedpersonnumberof wormsperinfectedperson alsoreferredtoasalsoreferredtoasworm burdenworm burden measureddirectlybycountingexpelled wormsduringmeasureddirectlybycountingexpelled wormsduring

treatment;indirectlybycountinghelmintheggstreatment;indirectlybycountinghelmintheggsexcretedinfecesexpressedasexcretedinfecesexpressedaseggspergrameggspergram (epg)(epg)

MorbidityMorbidity:: clinicalconsequencesofinfectionsthataffectan

individuals wellbeing


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DiagnosisDiagnosis

Demonstration of parasitesDemonstration of parasites E.g.eggs, adults, larvae, cysts, oocystsandtrophozoitesE.g.eggs, adults, larvae, cysts, oocystsandtrophozoites

Detection of host immune response to the parasitesDetection of host immune response to the parasites E.g.antibodiesandantigensE.g.antibodiesandantigens Inlightinfections whenparasitesarestillimmature,Inlightinfections whenparasitesarestillimmature,

immunoassaysmaybecomeusefulimmunoassaysmaybecomeuseful

Specimens for parasitic examination:Specimens for parasitic examination:stool, blood,stool, blood,urine, sputum, cerebrospinalfluid, tissueaspirate,urine, sputum, cerebrospinalfluid, tissueaspirate,tissuebiopsiesandorificeswabstissuebiopsiesandorificeswabs


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diagnosisdiagnosis

MicroscopyMicroscopy simple, informative, can establishsimple, informative, can establishrapid diagnosis; dependent on skill of microscopistrapid diagnosis; dependent on skill of microscopist

Limitedbylow densityofparasitesinspecimens;Limitedbylow densityofparasitesinspecimens;

maybeaffectedbystageofthedisease, biologyofmaybeaffectedbystageofthedisease, biologyoftheparasitetheparasite ParasiteconcentrationtechniquesParasiteconcentrationtechniques:requireadditional:requireadditional

equipment, suppliesandreagentsequipment, suppliesandreagents ParasiteculturemethodsParasiteculturemethods:requireacleanbenchand:requireacleanbenchand

specialculturemediaspecialculturemedia SpecialstainingproceduresofSpecialstainingproceduresoffluorescentfluorescent

microcopymicrocopy availableforbettervisualizationavailableforbettervisualization


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diagnosisdiagnosis

Molecular diagnosis: molecular or DNAMolecular diagnosis: molecular or DNA--based methodsbased methods Address problems associated with microscopy andAddress problems associated with microscopy and

immunodiagnosisimmunodiagnosis

DNAprobes, detection of specific nucleic acid sequencesDNAprobes, detection of specific nucleic acid sequences

Rapid diagnostic tests (RDTs)Rapid diagnostic tests (RDTs) Newer and more advanced methods of immunodiagnosisNewer and more advanced methods of immunodiagnosis

(antigen(antigen--capture tests)capture tests)

Detects fewer parasites; faster resultsDetects fewer parasites; faster results Easy to perform and require minimal training of personnelEasy to perform and require minimal training of personnel


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diagnosisdiagnosis

ImmunodiagnosisImmunodiagnosis

Overcome problems related to microscopicOvercome problems related to microscopicexaminationexamination

Detect antigen or antibodies in clinical specimensDetect antigen or antibodies in clinical specimens ImmunofluorescentAssayELISA, IndirectImmunofluorescentAssayELISA, Indirect

HemagglutinationAssay, RIA, anddotblotHemagglutinationAssay, RIA, anddotblot

Antibody detection testsAntibody detection tests LimitedindistinguishingactivefrompriorinfectionsLimitedindistinguishingactivefrompriorinfections UsefulindetectingexposureandetiologyofoutbreaksUsefulindetectingexposureandetiologyofoutbreaks

andinmappingfociofinfectionandinmappingfociofinfection Serveasalternatives whenmicroscopicexamfailsServeasalternatives whenmicroscopicexamfails


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TreatmentTreatment

DewormingDeworming::useofantihelminthicdrugsuseofantihelminthicdrugs

Cure rateCure rate:: no.(expressedaspercentage)ofpreviouslypositiveno.(expressedaspercentage)ofpreviouslypositive

su

bject

sfou

ndt

obeeggsu

bject

sfou

ndt

obeegg--negat

iveonexaminat

ionofnegat

iveonexaminat

ionofastoolorurinesampleatasettimeafterastoolorurinesampleatasettimeafterdewormingdeworming

IndicatorusedtomeasurereductioninprevalenceIndicatorusedtomeasurereductioninprevalenceofinfectionofinfection

Egg reduction rateEgg reduction rate (ERR):(ERR): percentagefallineggcountsafterdewormingpercentagefallineggcountsafterdeworming IndicatorusedtomeasurereductioninintensityofIndicatorusedtomeasurereductioninintensityof

infectioninfection


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Selective treatmentSelective treatment:: involvesindividualinvolvesindividual--leveldeworming withselectionleveldeworming withselection

fortreatmentbasedonadiagnosisofinfectionfortreatmentbasedonadiagnosisofinfection

Targeted treatmentTargeted treatment::

groupgroup--leveldeworming wherethe(risk)grouptobeleveldeworming wherethe(risk)grouptobetreated(withoutpriordiagnosis)maybedefinedbytreated(withoutpriordiagnosis)maybedefinedbyage, sex, orsocialcharacteristicsirrespectiveofage, sex, orsocialcharacteristicsirrespectiveofinfectionstatusinfectionstatus

Universal treatmentUniversal treatment:: populationpopulation--leveldewormingin whichthecommunityleveldewormingin whichthecommunity

istreatedirrespectiveofage, sex, infectionistreatedirrespectiveofage, sex, infectionstatus, orothersocialcharacteristicsstatus, orothersocialcharacteristics

TreatmentTreatment


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PreventionandControl Morbidity controlMorbidity control::

theavoidanceofillnesscausedbyinfectionstheavoidanceofillnesscausedbyinfections

InformationInformation--educationeducation--communicationcommunication (IEC):(IEC):

ahealtheducationstrategythataimstoencourageahealtheducationstrategythataimstoencourage

peopletoadaptandmaintainhealthylifepracticespeopletoadaptandmaintainhealthylifepractices

Environmental managementEnvironmental management::

manipulationofenvironmentalfactorsortheirmanipulationofenvironmentalfactorsortheir

interaction withhumanbeingsinteraction withhumanbeings aim:preventorminimizevectororintermediatehostaim:preventorminimizevectororintermediatehost

propagation & reducecontactbetweenhumansandpropagation & reducecontactbetweenhumansandtheinfectiveagenttheinfectiveagent


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Environmental sanitationEnvironmental sanitation::interventionstointerventionstoreduceenvironmentalhealthrisksreduceenvironmentalhealthrisks Includes safe disposal and hygienic management ofIncludes safe disposal and hygienic management of

human and animal excreta, refuse and waste waterhuman and animal excreta, refuse and waste water

Involves the control of vectors, intermediate hosts,Involves the control of vectors, intermediate hosts,and reservoirs of diseaseand reservoirs of disease

provision of safe drinking water and food safetyprovision of safe drinking water and food safety

PreventionandControl


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EradicationversusElimination

Disease eradicationDisease eradication:: permanentreductiontozeroofthepermanentreductiontozeroofthe worldwideworldwide incidenceofincidenceof

infectioncausedbyaspecificagent, asaresultofdeliberateinfectioncausedbyaspecificagent, asaresultofdeliberateeffortsefforts

continuedmeasuresnolongerneededcontinuedmeasuresnolongerneeded

Disease eliminationDisease elimination:: reductiontozerooftheincidenceofareductiontozerooftheincidenceofaspecifieddiseaseinaspecifieddiseaseina

definedgeographicareadefinedgeographicarea asaresultofdeliberateeffortsasaresultofdeliberateefforts

Continuedintervention/surveillancestillrequiredContinuedintervention/surveillancestillrequired


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Host-Parasite Relationships


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Mechanisms by which parasites cause injury toMechanisms by which parasites cause injury tothe hostthe host

Mostcommon:Mostcommon:interferenceinterference withthevitalprocessesofwiththevitalprocessesofthehostthehostthroughtheenzymesystemsthroughtheenzymesystems

Secretoryandexcretoryproductsofparasitesallow themtoSecretoryandexcretoryproductsofparasitesallow themtometabolizenutrientsfromthehostmetabolizenutrientsfromthehost

Ex:E.histolyticatrophozoitessecretecysteineproteinasesEx:E.histolyticatrophozoitessecretecysteineproteinases--digestcellularmaterials & anddegradeepithelialbasementdigestcellularmaterials & anddegradeepithelialbasementmembranefacilitatingtissueinvasionmembranefacilitatingtissueinvasion

InvasionanddestructionofhosttissueInvasionanddestructionofhosttissue Plasmodiuminvadesrbc, andcausesitsrupturePlasmodiuminvadesrbc, andcausesitsrupture

Deprivationofthehostofessentialnutrients &Deprivationofthehostofessentialnutrients &substancessubstances

HeavyhookworminfestationcausesirondeficiencyanemiaHeavyhookworminfestationcausesirondeficiencyanemia


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Effectsofthe Hostonthe Parasite

Genetic makeGenetic make--up of the hostup of the host influencetheinteraction withtheparasiteinfluencetheinteraction withtheparasite sicklesickle--celltraitconferssomeprotectionfromcelltraitconferssomeprotectionfrom

FalciparummalariaFalciparummalaria

Nutritional statusNutritional status of the hostof the host highproteindietnotsuitableforthedevelopmenthighproteindietnotsuitableforthedevelopment

ofintestinalprotozoanofintestinalprotozoan

Immune processesImmune processes AcquiredimmunityimportantinmodifyingseverityAcquiredimmunityimportantinmodifyingseverity

ofdiseaseinendemicareasofdiseaseinendemicareas


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Hostimmune response toparasiticHostimmune response toparasiticinfect

ion

infect

ion

WelldefinedgeneticcontrolWelldefinedgeneticcontrol

Parasiteantigensareprocessedandpresentedto TParasiteantigensareprocessedandpresentedto Thelperlymphocytes(Th1or Th2)helperlymphocytes(Th1or Th2)---->produce>producelymphokineslymphokines bringaboutCMI responseorantibodybringaboutCMI responseorantibodyproductionproduction

Antibodiesinvolved: IgE, IgG, IgM & IgAAntibodiesinvolved: IgE, IgG, IgM & IgA


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Hostimmune response toparasiticHostimmune response toparasiticinfectioninfection

Mostcommonresponse:Mostcommonresponse: eosinophilia & elevatedserum IgEeosinophilia & elevatedserum IgE

Ex.markedimmunologicresponseinEx.markedimmunologicresponseinAngiostrongyluscantonensisand T.canisAngiostrongyluscantonensisand T.canis

Bo

und Ig

Ean

tibodiesmedia

te

Bo

und Ig

Ean

tibodiesmedia

teexpulsionofadultGI helminthsexpulsionofadultGI helminths


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Hostimmune response toparasiticinfectionHostimmune response toparasiticinfection

IgG1 and IgEIgG1 and IgE actonmastcells & basophilsactonmastcells & basophils degranulation &degranulation &

eventualreleasepharmacologicallyactivesubstanceseventualreleasepharmacologicallyactivesubstances----> Type1hypersensitivityreactioncalled> Type1hypersensitivityreactioncalledanaphylaxisanaphylaxis

Ex:ruptureoflarvalinfection withEx:ruptureoflarvalinfection withE.granulosusE.granulosus

IgG and IgM:IgG and IgM:preventpenetrationofrbcsbypreventpenetrationofrbcsby PlasmodiaPlasmodiaspp & Babesiasppspp & Babesiaspp

Secretory IgA:Secretory IgA:protectagainstmetacestode & GI infxnsprotectagainstmetacestode & GI infxns

IgM & IgA:IgM & IgA:mediateantibodydependentcellmediatedmediateantibodydependentcellmediatedcytotoxicityincytotoxicityin G.lambliaG.lamblia infectioninfection


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Parasite EvasionmechanismsParasite Evasionmechanisms

Immune suppressionImmune suppression

reduceimmunefunctionofmacrophagesleadingtodefectivereduceimmunefunctionofmacrophagesleadingtodefectiveantigenprocessinginantigenprocessingin PlasmodiumPlasmodium infectioninfection

Antigenic variationAntigenic variation

surfaceproteinvariationseeninsurfaceproteinvariationseenin T. gambienseT. gambiense &&

G.lambliaG

.lamblia infec

tioninfec

tion

Host mimicryHost mimicry

tegumentoftegumentof Schistosoma sppSchistosoma spp adult can acquire antigenicadult can acquire antigenicmoleculesfromthe hostmoleculesfromthe host

Intracellular sequestrationIntracellular sequestration

Trypanosoma & LeishmaniaTrypanosoma & Leishmania proliferate in macrophages &proliferate in macrophages &escapethe host immune responseescapethe host immune response


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Adverse effectsofImmune Response toAdverse effectsofImmune Response tothe hostthe host

Intense or abnormal immune responses may result inIntense or abnormal immune responses may result inpathological manifestationspathological manifestations

T. cruziT. cruzi -- massive damage not only to infected cells but also tomassive damage not only to infected cells but also to

surrounding nerve cells and myofiberssurrounding nerve cells and myofibers RecurrentPlasmodium infection, immune complexes areRecurrentPlasmodium infection, immune complexes are

associated with Hyperactive Malarious Splenomegaly (HMS)associated with Hyperactive Malarious Splenomegaly (HMS) ----patients suffer from persistent splenomegaly and anemiapatients suffer from persistent splenomegaly and anemia

In P. malariae infection, these immune complexes are depositedIn P. malariae infection, these immune complexes are depositedin glomerular basement membranein glomerular basement membrane ----> kidney failure and> kidney failure and

nephritic syndromenephritic syndrome


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Groups of parasites with medical and publicGroups of parasites with medical and public

health importancehealth importance

Parasitic infectionsParasitic infections

Uni llul r r t z n

Multi llul r t z n


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Metazoan parasites

Helminths arthropods

AnnelidsEx: leeches

Nematodes flatworms

cestodes

trematodes

Kingdom

Protista

Sarcomastigophora ApicomplexaMicrosporaCiliophora


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ProtozoaProtozoaAll protozoa fall under Kingdom ProtistaAll protozoa fall under Kingdom Protista

Nucleus/nucleiNucleus/nuclei

CytoplasmCytoplasm

Outer limiting membraneOuter limiting membrane Cellular elaborations:organellesCellular elaborations:organelles

Locomotory r tusCili , fl g ll ,seudopodi

Many requirea wet environment for feeding, locomotion,

osmoregulationand reproductionform infectivestagescalledcysts w ichare resistant to

environmental changescompared to thevegetativestages

calledtrophozoite


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ProtozoansProtozoansPhylumPhylum Organelle of locomotionOrganelle of locomotion

Phylum SarcomastigophoraPhylum Sarcomastigophora

SubphylumMastigophora:SubphylumMastigophora:SubphpylumSarcodina:SubphpylumSarcodina:

Flagella(whipFlagella(whip--likestructures)likestructures)

Pseudopodia(footPseudopodia(foot--likeextrusions)likeextrusions)

Phylum CiliophoraPhylum Ciliophora Cilia(hairCilia(hair--likeprojections)likeprojections)

Phylum Apicomplexa:Phylum Apicomplexa: apicalcomplexattheanteriorendapicalcomplexattheanteriorendconsistingofpolarrings,consistingofpolarrings,

subpelliculartubules, conoid,subpelliculartubules, conoid,rhoptries, andmicronemesrhoptries, andmicronemes

Phylum MicrosporaPhylum Microspora ExtrusionapparatustoinsertExtrusionapparatustoinsertinfectivematerialtothehostinfectivematerialtothehostcellcell


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ClassificationofProtozoanparasitesClassificationofProtozoanparasites

phylumphylum subphpylumsubphpylum speciesspecies

SarcomastigophoraSarcomastigophora--MastigophoraMastigophora

SarcodinaSarcodina

Chilomastix mesnili Dientamoeba fragilisGiardia lamblia

Trichomonas hominis, T. tenax, T. vaginalis

Leishmania braziliensis, L. donovani. L. tropica

Trypanosoma brucei complex, T. cruzi

Acanthamoeba castellani Endolimax nana

Entamoeba coli, E. dispar, E. histolytica

Iodamoeba butschlii Naegleria fowleri

CiliophoraCiliophora Balantidiium coli

ApicomplexaApicomplexa Babesia spp Cryptosporidium hominis

Isospora belli Cyclospora cayatenensisPlasmodium spp. Toxoplasma gondii

MicrosporaMicrospora Enterocytozoon bineusi Encephalitozoon spp.Vittaforma cornea Pleistophora spp.

Trachipleistophora hominis Microsporidium spp.

Brachiola vesicularum


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Classificationof metazoan parasitesClassificationof metazoan parasites

Nematoda

Intestinal

Extra-intestinalAscaris, Capillaria, Enterobius, Hookworm, Strongyloides,

richuris

Angiostrongylus, filaria, richinella

Cestoidea

Cyclophyllidea

Pseudophyllide

a

Dipylidium, Echinococcus, Hymenolepis, Raillientina,

aenia

Diphyllobothrium, Spirometra

Trematoda Artyfechinostomum, Clonorchis, Echinostoma, ascioloa,asciolopsis, Heterophyids, Opisthorchis, Paragonimus,

Schistosoma

Arthropods

Arachnida

Chilopoda

Crustacea

Diplopoda

Insect

a

Mites, scorpions, spiders, ticks

centipedes

Copepods, crabs

millipedes

Flies, flea, beetle, lice, w

asp, bugs, mosquitoes


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NematodesNematodes

Elongated, cylindrical, with bilateral symmetry & aElongated, cylindrical, with bilateral symmetry & acomplex digestive tractcomplex digestive tract

Provided with separate sexes; some may beProvided with separate sexes; some may beparthenogeneticparthenogenetic

w/ sensory organs in the anterior (amphids) & posteriorw/ sensory organs in the anterior (amphids) & posteriorends (phasmids)ends (phasmids) Those with phasmids are called phasmids nematodesThose with phasmids are called phasmids nematodes

Without phasmids: aphasmids nematodesWithout phasmids: aphasmids nematodes

3 aphasmids worms of medical importance:3 aphasmids worms of medical importance: Trichuris, Trichinella and CapillariaTrichuris, Trichinella and Capillaria


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Cestodes: tapewormsCestodes: tapeworms Belong to PlatyhelminthesBelong to Platyhelminthes

Dorsoventrally flattened withDorsoventrally flattened withbilateral symmetrybilateral symmetry

Segmented, ribbonSegmented, ribbon--likelikeappearanceappearance

Adult tapeworms areAdult tapeworms arehermaphroditichermaphroditic Provided with a scolex (mainProvided with a scolex (main

attachment to the host)attachment to the host) ---- neckneckregion, from it will startregion, from it will startsegmentation or strobilizationsegmentation or strobilization


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QuickTime and aTIFF ( ncompressed) decompressor



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Cestodes: tapewormsCestodes: tapeworms 2 orders with medical importance:Pseudophyllidea &Cyclophyllidea2 orders with medical importance:Pseudophyllidea &Cyclophyllidea

PseudophyllideanPseudophyllidean

tapewormstapeworms

CyclophyllideatapemwormsCyclophyllideatapemworms

scolexscolex SpatulatescolexwithSpatulatescolexwith

suckinggrovescalledsuckinggrovescalled

bothriabothria

globularwith 4 muscularsuckersglobularwith 4 muscularsuckers

GenitalporesGenitalpores PresentbuthasauterinePresentbuthasauterine

porewhichallowsreleaseofporewhichallowsreleaseof

eggsfromgraviduteruseggsfromgraviduterus

Presentbutwithout uterinepore,Presentbutwithout uterinepore,

insteadundergotheprocessofinsteadundergotheprocessof

apolysiswherebygravidsegmentsapolysiswherebygravidsegments

aredetachedfromthemainbodyandaredetachedfromthemainbodyand

eggsareeventuallyreleasedeggsareeventuallyreleased

RecoveryofRecoveryof

botheggsbotheggs

andand

segmentssegments

SegmentsarenotgenerallySegmentsarenotgenerally

foundfound

BotheggsandsegmentsareBotheggsandsegmentsare

recoveredfrompatientsrecoveredfrompatients


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PseudophyllideanPseudophyllidean

tapewormstapeworms

CyclophyllideaCyclophyllidea

tapewormstapeworms

eggseggs Eggsareoperculated &Eggsareoperculated &

immatureand requiresimmatureand requires

aquaticdevelopment of theaquaticdevelopment of the

embryocalledcoracidiumembryocalledcoracidium

Eggasarenonoperculated &Eggasarenonoperculated &

arepassedout readillyarepassedout readilly

containing thehexacaanthcontaining thehexacaanth

embryoembryo

IntermediatIntermediat

ehostsehosts

Requires 2 IH; In the 1st IH,Requires 2 IH; In the 1st IH,

eggsencyst asprocercoid.eggsencyst asprocercoid.

In the 2nd IH: aspleorcercoidIn the 2nd IH: aspleorcercoid

larvaelarvae

This isbest representedbyThis isbest representedby

Diphyllobothrium whichDiphyllobothrium which

causesadult infectionandcausesadult infectionandSpirometra whichcausesSpirometra whichcauses

larval infection inmanlarval infection inman

Only 1 IH, but diffspeciesOnly 1 IH, but diffspecies

prod. diff typesofencystedprod. diff typesofencysted

larvae in the IHlarvae in the IH

Ex. TaeniaproduceEx. Taeniaproduce

cysticercus typecysticercus type

Hymenolepis, DipylidiumandHymenolepis, Dipylidiumand

raillietinaproduce theraillietinaproduce thecysticercoid typecysticercoid type

EchinococcusproduceEchinococcusproduce

hydatidhydatid

Infection w/ adult tapeworms is through theconsumptionofinfected intermediatehosts

Someare infected w/ the larval stageofT. soliumcalledcysticercosisandof Echinococcusspp. calledhydatidcyst


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trematodestrematodes

Generally grouped based on their habitat.Generally grouped based on their habitat.

Adult schistosoomes are found in theAdult schistosoomes are found in themesenteric veinsmesenteric veins ----> blood flukes> blood flukes

AdultAdult ParagonimusParagonimus found in the lungfound in the lungparenchymaparenchyma

Flukes that inhabit the liver and bileFlukes that inhabit the liver and bilepassages:passages: Fasciola, Clonorchis & OpisthorchisFasciola, Clonorchis & Opisthorchis

Flukes that inhabit the intestines:Flukes that inhabit the intestines:Fasciolopsis, Echinostoma and HeterophyidsFasciolopsis, Echinostoma and Heterophyids


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ArthropodsArthropods

Bilaterally symmetrical organisms withBilaterally symmetrical organisms withsegmented and jointed appendages.segmented and jointed appendages.

Chitinous exoskeleton covers the bodyChitinous exoskeleton covers the body

Includes: insects, mites, ticks, spiders,Includes: insects, mites, ticks, spiders,scorpions, centipedes, millipedes andscorpions, centipedes, millipedes and

crustaceanscrustaceans


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Parasitology an Introduction

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