Echinococcus granulosus
Echinococcus granulosus
• Hydatid disease
• Cosmopolitan
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Mediterranean countries
Russian federation
China
North and East Africa
Australia
South America
North America: Deep South and Far West
Echinococcus granulosus
ADULT MORPHOLOGY - small tapeworm - 3-6 mm long
• consists of scolex, neck, immature proglottid, mature
proglottid, and gravid proglottid
Carnivore
Herbivore
Humans
10-30 scolices per
Pathogenesis
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Hydatid cyst
Slow growth
Asymptomatic for years
Up to 20 years (unless in
nervous system)
• Pathology depends on
– Location
– Size
– How many
Pathogenesis
• Crowds host tissues
• Destroys tissues-replaces with cyst
• Grows continuously
– 15 quarts of fluid
– Millions of scolices
• Rupture of the cyst fatal
– Anaphylactic shock hydatid fluid (death)
• In most herbivores, cysts do not keep
growing
Unilocular
hydatid cyst in the
lung
Note pressure
effects exerted by
cyst that crowds
and destroys lung
tissue
Hydatid Cyst
Diagnosis
• Physical imaging
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MRI
CT scan
Ultrasound
X-ray
• Serodiagnosis
Hydatid Cyst of Echinococcus
granulosus
Treatment
• Surgery
– Preoperative chemotherapy-albendazole
– Protoscolicidal compounds
• Ethanol
• Saline
• Formalin
• Recurrence
– 50%
– Undetected cysts
– Inadequate removal
• Mebendazole
– 48% of cysts
Epidemiology
• How do people get infected?
• How do eggs get into environment?
• How do we ingest them?
Epidemiology
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Human-Dog
Herbivores: Sheep, goats, camels, rabbit
Sheep raising areas
Offal
Epidemiology
• Human-Dog contact
Epidemiology
• Human-wildlife contact
Echinococcus granulosus
Complex
• Echinococcus granulosus comprises
multiple species
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Life cycle patterns
Host specificity
Development Rate
Antigenicity
Transmission dynamics
Chemotheraputic drug response
Pathology
Control
• Sheep vaccine successful
Echinococcus multilocularis
Life Cycle of Echinococcus
multilocularis
1. Adult tapeworm occurs
in intestine of foxes.
Dogs, cats, and coyotes can
also serve as definitive hosts.
• Adult is small - 1-2 mm
long
Echinococcus multilocularis
Alveolar hydatid cyst in a mouse - cyst metastasizes from
the liver to fill the body cavity
Alveolar Hydatid Cyst
Echinococcus multilocularis
• Liver
• Cyst multilocular
hydatid
• External budding
• Extend processes
throughout tissues
• Cirrhosis of liver
• Thinner membrane
• Metastasis
– Advanced cases
Echinococcus multilocularis
• Not easily operable
– timing
• Chemotherapy
– Praziquantel can increase growth
– Mebendazole and albendazole given throughout
the life of the patient.
• retards growth
• Not easily treatable
Echinococcus multilocularis
• Fox tapeworm
• Europe, Asia, Americas, New Zealand
Echinococcus multilocularis
This species has recently been reported in the upper Midwest
(North and South Dakota, Minnesota, Iowa, Nebraska,
southern Wisconsin, and Indiana). Recently identified in
Illinois, Ohio and Missouri.
Epidemiology
• Increasing in Europe
• Up to 1980’s only in France, Switzerland, Germany, and
Austria
• Spreading throughout Europe.
Epidemiology
• Increase in fox infection
• Increase in human infection
– Still rare
• Switzerland and Germany
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Antirabies vaccines
Increased fox abundance
Movement of foxes
Encroachment on urban areas
Contact with domestic dogs
Hymenolepis
Hymenolepis
• Hymenolepis diminuta
– Rare in humans
– 90 cm
– Model tapeworm
• Hymenolepis nana
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“Dwarf tapeworm” 40 mm long
Common in humans
97.3% children in Moscow
1% children in SE US
Cysticercoid
Hymenolepis nana
D
A
1
B
3
4
C
2
Pathogenesis and Treatment
• Similar to Adult species of Taenia
• Praziquantel
Dipylidium caninum
Dipylidium caninum
• Most common tapeworm of
dogs
• Cats, humans
• 2 sets of reproductive organs
Gravid
proglottids
shed
Dog eats
flea
Infective stage?
Diagnostics
Pathogenesis and Treatment
• Similar to Adult species of Taenia
• Praziquantel