Transcript Echinococcus granulosus (and multilocularis)

Echinococcus
granulosus (and
multilocularis)
Sarah Richards
Max Karpyak
Three Species
 Echinococcus granulosus: causing
hydatid disease
 Echinococcus multilocularis: causing
alveolar hydatid disease
 Echinococcus vogeli: causing hydatid
disease
Echinococcus multilocularis
vs Echinococcus granulosus
 Both produce hydatid
disease in many
mammals, including
rodents and humans
 Unlike E. granulosus,
E. multilocularis
produces many small
cysts that spread
throughout the
infected animal
Geographic Distribution
 Worldwide
 Higher prevalence in South America
(Argentina, Uruguay), Europe
(Mediterranean bassin), Northern Africa,
Middle East, South Central and East Asia
Larvae Stage
 E. granulosus
 Hydatid cysts are large,
roughly spherical, fluid
filled hollow bladders
containing numerous
protoscolices.
 They vary in size; those
found in the liver are
aprox. 20 cm in diameter,
but those found in the
peritoneal cavity are
usually larger
 E. multilocularis
 The cyst grows invasively
by external budding,
forming a diffuse growth
through the infected
organ, replacing that
organs tissues. In
contrast to E. Granulosus
this growth is very rapid,
infective prosocialises
being present only 2 to 3
months.
Adult Stage
 E. multilocaris
 Slightly smaller than
E. granulosus (max.
length of aprox 4 mm
and consisting of 4-5
proglottids).
 E. granulosus
 The adult parasites in
the dog represent one
of the smallest of the
tapeworms (3-9 mm
in length, usually with
3 proglottids).
 Scolex is globular in
shape and has a
prominent rostellum
Definitive Hosts
E. granulosus
 Dogs
 Coyotes
 Wolves
E. multilocularis
 Mostly foxes
Intermediate Hosts
E. granulosus
 Sheep
 Horses
 Camels
 Pigs
 Humans
E. multilocularis
 Small rodents
Life Cycle: E. granulosus
 The adult is in the small bowel of the definitive host
 Gravid proglottids release eggs that are passed in the
feces
 In the intermediate host the egg hatches in the small
bowel and releases an oncosphere
 The oncosphere penetrates the intestinal wall and
moves through the circulatory system to various organs
 In the organs they develop into cysts and enlarge
gradually
 The cysts produce protoscolices and daughter cysts
 Definitive host eats the infected organs and becomes
infected
 After ingestion, the protoscolices evaginate, attach to
the intestinal mucosa and develop into adult stages
 In 32-80 days, the cycle starts over
Life Cycle: E. multilocularis
 The life cycle is basically the
same E. granulosus
Except
 There are different definitive
and intermediate hosts
 Larval growth in the liver
remain indefinitely in the
proliferative stage, which
causes invasion of the
surrounding tissues
(sometimes this can take over
the whole organ)
Life Cycle (cont’d)
Diagnosis
 Diagnosis in the definitive host is difficult by
ordinary microscopy because it will look a lot
like Taenia and Echinococcus eggs
 Detection of antigens in feces by ELISA is
currently the best available technique
 Newer techniques like polymerase chain
reaction (PCR) is also used to identify the
parasite from DNA isolated from eggs or feces
Treatment
 Surgery: with the goal of leaving the cyst
intact so new cysts do not form
 Mebendazole can be taken over a long
period of time at low dosages
 Praziquantel
Prevention
 The best way to keep
dogs from being
infected is to prevent
them from eating
infected feces, or
contaminated meat
 The best way to
avoid human
infection is to avoid
ingesting food or
other substances
contaminated with
dog feces
Prevention (cont’d)
 The best method is to disrupt the lifecycle
 Basic hygiene practices
 Avoid feeding raw offal (internal organs of
butchered animals) to dogs
 By doing this hydatids have been virtually
eliminated in New Zealand (a once common
place for this parasite)
QUESTIONS
 1. What are the main differences
between the larvae stage of E.
granulosus and E. multilocularis?
 E. granulosus
 Hydatid cysts are large,
roughly spherical, fluid
filled hollow bladders
containing numerous
protoscolices.
 They vary in size; those
found in the liver are
aprox. 20 cm in diameter,
but those found in the
peritoneal cavity are
usually larger
 E. multilocularis
 The cyst grows invasively
by external budding,
forming a diffuse growth
through the infected
organ, replacing that
organs tissues. In
contrast to E. Granulosus
this growth is very rapid,
infective prosocialises
being present only 2 to 3
months.
2. What are the definitive hosts for each
parasite?
E. granulosus
 Dogs
 Coyotes
 Wolves
E. multilocularis
 Mostly foxes