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EchinococciasisHydatidosisHydatid Disease
LECTURER
TOPIC
Kingdom AnimaliaPhylum PlatyhelminthesClass CestodaOrder CyclophyllideaFamily TaeniidaeGenus EchinococcusSpecies E. granulosus
Echinococcus granulosus
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OverviewOrganism HistoryEpidemiologyTransmissionDisease in HumansDisease in AnimalsPrevention and Control
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The OrganismCestode parasites Family TaeniidaeCurrently recognized species
Echinococcus granulosus Echinococcus multiocularis Echinococcus vogeli Echinococcus oligarthrus Echinococcus shiguicus
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The OrganismEchinococcus granulosus Cystic echinococcosis Unilocular echinococcosis Cystic hydatid diseaseMultiple species and strainsE. granulosus sensu lato General term for all species and strains
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The OrganismE. multilocularis Alveolar echinococcosis Alveolar hydatid disease Multilocular echinococcosis Multivesicular hydatidosisMultiple strains Less distinct than E. granulosa s.l. E. shiquicus a distinct species?
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The OrganismEchinococcus vogeli and Echinococcus oligarthrus Polycystic echinococcosis Unicystic echinococcosis
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The Organism:Zoonotic Species
G1 (sheep strain) E. granulosus s.l. Most frequent cause of disease in humansOther species may be important regionally
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In endemic areas dogs often have ready access to viscera from slaughtered livestock
as seen in this picture
Transmission of cystic hydatid disease Sheep slaughtering close to free-ranging
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DistributionE. multilocularis Northern hemisphere
Eurasia, Europe, North AmericaE. vogeli, E. oligarthrus Central and South AmericaE. shiquicus China
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TransmissionIndirect life cycle Definitive hosts ingest cysts in tissues of intermediate hosts Cysts develop into tapeworms Gravid proglottids or eggs shed in feces by definitive host Eggs ingested by intermediate hosts
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Transmission: E. granulosus s.l.Definitive hosts Canids Felids HyaenidsIntermediate hosts Herbivores Humans
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Transmission: E. multilocularisDefinitive hosts Wild carnivores (e.g., fox) Domestic dogs and catsIntermediate hosts Small mammals (rodents) Domesticated mammals Humans
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E. vogeliDefinitive hosts
Bush dogsDomestic dogs
Intermediate hostsSouth American rodents (e.g., pacas)
E.oligarthrusDefinitive hosts
Wild felidsIntermediate hostsRodents
Transmission
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Zoonotic TransmissionHumans act as intermediate hostsIngest tapeworm eggs shed by definitive hosts Contaminated fruits, vegetables,herbs, water
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Disease in HumansIncubation period Month to years 20 to 30 years documented for cysts that grow slowly and are not in a
critical locationClinical signs Depend on size, number and location of metacestodes
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Disease in Humans:E. granulosus s.l.
May be asymptomaticUsually one cyst presentCyst location 60 to 70% in liver 20 to 25% in lungsSymptoms dependent on cyst location
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Disease in Humans:E.multilocularis
Cysts usually found in liverCysts not enclosed within membrane Invade surrounding tissues Disease is progressive and malignantMay be asymptomatic if cyst dies early in
development
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Disease in Humans: E. vogeli, E. oligarthrus
Cysts usually originate in liver Can spread to nearby organs/tissuesSymptoms dependent on cyst location
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DiagnosisImaging techniques Ultrasound, radiology,MRI, CTSerologyBiopsyDetection of protoscolices Cyst fluid, sputumPCR
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TreatmentSurgical removal of cysts May not be possible to remove entire cyst depending on size and locationAnti-parasiticsWait-and-see Small, inactive cystsLiver transplant
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Disease in AnimalsIncubation period Months to years
20 to 30 years documentedClinical signs Depend on cyst size, number, location Often asymptomatic until cysts invade adjacent tissues/organs
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Clinical Signs: Definitive HostsUsually asymptomatic Even with heavy parasite burdenDisease rarely occurs Enteritis Diarrhea
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Clinical Signs: Intermediate HostsE. granulosus s.l. Cysts grow slowly Asymptomatic until surrounding tissues/organs become involved
Livestock typically slaughtered before this occurs Liver and lung most affected
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Clinical Signs:Intermediate HostsE. multilocularis Cysts most often found in liver Metastatic lesions occur in other organs
Lungs, brain Rodents may die within weeks of infection
Multiple organs affected
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Clinical Signs: Intermediate HostsE. vogeli, E. oligarthrus Not documented in domesticated animal intermediate hosts Zoo outbreaks
Nutrias Nonhuman primates
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Post Mortem LesionsNo lesions in definitive hostsIntermediate hosts Cysts grossly apparent
E. granulosus s.l. Fluid-filled Fibrous wall Liver, lungs, other internal organs
E. multilocularis Liver, lungs, CNS Multilocular, semisolid Lobulated
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Diagnosis: Definitive HostsRoutine fecal testing not appropriate Cannot differentiate from Taenia spp. Tiny proglottids in feces not noticeableELISA Screening for definitive hostsPCR Fecal samplesMorphology
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Diagnosis: Intermediate HostsUsually discovered at necropsyHistologyAntigen detectionPCRSerology Not generally used in domestic animals
Poor response in usual intermediate hosts
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TreatmentAnthelmintic drugs PraziquantelSurgery Intermediate hosts Follow with long term daily anti-parasitics
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Prevention in HumansControl echinococcosis in domestic animals Don’t feed livestock entrails to dogs Don’t allow dogs and cats to hunt Regularly test and/or treat animals allowed outside
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Prevention in HumansMinimize risk of egg ingestion Wash fruits and vegetables Wash hands frequently Avoid untreated water sources Do not handle wild carnivores or their carcasses Thoroughly cook meat before eating
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Prevention in HumansWear personal protective equipmentRegular surveillance Laboratory personnel Children exposed to feces of infected animalsNo vaccine
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Prevention in AnimalsRegular surveillanceTreat infected animals (dogs) Praziquantel Multiple doses requiredVaccination Recombinant
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