3. 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
4. Geographic Distribution
Worldwide
Higher prevalence in South America (Argentina,
Uruguay), Europe (Mediterranean bassin),
Northern Africa, Middle East, South Central and
East Asia
5. 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.
6. 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
9. 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
10. 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)
12. 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
13. 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
14. 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
15. 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)
16. 1. What are the main differences between the
larvae stage of E. granulosus and E. multilocularis?
17. 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.
18. 2. What are the definitive hosts for each parasite?
20. Echinoccocus
is caused by infection with the larval stage of Echinococcus
granulosus. CE is found in Africa, Europe, Asia, the Middle East,
Central and South America, and in rare cases, North America. The
parasite is transmitted to dogs when they ingest the organs of
other animals that contain hydatid cysts. The cysts develop into
adult tapeworms in the dog. Infected dogs shed tapeworm eggs
in their feces which contaminate the ground. Sheep, cattle, goats,
and pigs ingest tapeworm eggs in the contaminated ground;
once ingested, the eggs hatch and develop into cysts in the
internal organs. The most common mode of transmission to
humans is by the accidental consumption of soil, water, or food
that has been contaminated by the fecal matter of an infected
dog. Echinococcus eggs that have been deposited in soil can
stay viable for up to a year. The disease is most commonly found in
people involved in raising sheep, as a result of the sheep's role as
an intermediate host of the parasite and the presence of working
dogs that are allowed to eat the offal of infected sheep.
21. Alveoccocus
is caused by infection with the larval
stage of Echinococcus multilocularis. AE is
found across the globe and is especially
prevalent in the northern latitudes of
Europe, Asia, and North America. The
adult tapeworm is normally found in
foxes, coyotes, and dogs. Infection with
the larval stages is transmitted to people
through ingestion of food or water
contaminated with tapeworm eggs.
