Transcript T. solium

Cestode (tapeworm,绦虫)
GENERAL INTRODUCTIONS

Taxonomic position
Phylum platyhelminthes
Class Cestoda
Order Cyclophyllidae
Order Pseudophyllidae
MORPHOLOGICAL FEATURES
Flat and Segmented
 Scolex-equipped with organs of attachment:
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 suckers,
hooks, grooves
Neck - germinal portion
 Strobila:
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Proglottids
Immature proglottid
Mature proglottid
gravid proglottid
MORPHOLOGICAL FEATURES
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Body wall: Tegument and
subtegument (syncytial layer);
no coelomic cavity
Monoecious
Digestive system: completely
degenerated
PHYSIOLOGY AND PATHOGENESIS
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Surface absorption capabilities
Highly developed reproductive
functions
Anaerobic metabolism
All species are parasitic
Pathogenic stage may be adult or the
larva
LIFE CYCLE PATTERNS
1. Pseudophyllidae type
 Scolex provided 2 grooves - bothrium
 Need two intermediate hosts
 aquatic crustaceans
 fish or other vertebrate animals
 Life stages
copepod
eggcoracidium  procercoid plerocercoid(sparganum)
 adult worm
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Spirometra mansoni – cause sparganosis
Diphilobothrium latum – accidental infection in
humans
LIFE CYCLE PATTERNS
2. Cyclophyllidae type
 Scolex provided 4 suckers sometimes supplemented with
circular of hooks
 Need one intermediate host only -- usually mammals
 Life stages
egg hexacanth metacestode stage  adult worm.
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Taenia solium
Teania saginata
Echinococcus granulosus
E. multilocularis
Hymenolepis spp
Metacestode stage
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Larval stage of a cestode that develop in
the intermediate host.
 Cysticercus - Taenia spp.
 Hydatid cyst - Echinococcus granulosus
 Alveolar hydatid cyst - E. multilocularis
 Cysticercoid - Hymenolepis spp.
Important species
Taenia solium
Teania saginata
Echinococcus granulosus
Spirometra mansoni
Hymenolepis nana
Hymenolepis diminuta
Taenia solium (猪带绦虫)
Taenia saginata (牛带绦虫)
Taenia solium
GENERAL INTRODUCTION
• Worldwide distribution
• Large tapeworm
• Larval infection of Taenia solium may cause
serious clinical disease ---CYSTICERCOSIS
Morphology
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Can be up to 2 to 4 meters long
It has a globular scolex with four suckers and 2
circular rows of hooks (rostellum)
The gravid proglottids are 5×10 mm with a 7-13
branched uterus
The eggs of T. solium and T. saginata are
indistinguishable
scolex of T. solium.
Gravid proglottids of Taenia solium.
Injection of India ink in the uterus
allows visualization of the primary
lateral branches. T. solium has 7 13 branches on each side. Note the
genital pores in mid-lateral position.
Taenia solium
eggs of Taenia solium and T. saginata
The eggs are rounded or subspherical, diameter 31 - 43 µm, with a thick
brown embryophore. Inside each egg is an embryonated oncosphere with 6
hooks. A complete egg always has the primary membrane (shell) that
surrounds eggs.
Cysticercus
Life cycle of T.solium
Main points of the life cycle
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Man is the only definitive host, but he can also
be the intermediate host for T.solium
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Pig is the important intermediate host for
T.solium
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Adult worm reside in the lumen of the upper
part of small intestine
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The infective stage to man are both egg/gravid
proglottid and cysticercus for T.solium
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A tapeworm larval cyst (cysticercus) is ingested
with poorly cooked rice-like meat
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The larva escapes the cyst and passes to the
small intestine where it attaches to the mucosa by
the scolex suckers
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The proglottids develop as the worm matures in 3
to 4 months
Main points of the life cycle
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The adult may live in the small intestine as
long as 25 years and pass gravid proglottids
with the feces
When eggs consumed by pigs in which they
hatch and form cysticerci
T.solium eggs can also infect humans and
cause cysticercosis (larval cysts in lung, liver,
eye, maxillofacial region and brain)
 Eggs from ----auto-infection, external
 Eggs from ----auto-infection, internal
 Eggs from ----external
auto-infection
internal
man
Egg
man
external
Egg
auto-infection
external
Pathogenesis and clinical features
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Adult worm —Teaniasis
Light infections remain asymptomatic
Heavier infections may produce
abdominal discomfort, epigastric pain,
vomiting and diarrhea
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Metacestode stage –Cysticercosis
 The cysticercus stage of T. solium can be found
anywhere in the body -- subcutaneous, muscles, eye,
brain
 Regardless of the tissue affected, pathological
consequences are those of a space-occupying lesion
 Cysticerci in brain tend to grow a larger size than those
in other tissues
 The process of calcification may be accompanied by the
release of antigens -- inflammatory reaction
Cysticercosis
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The incidence of cerebral cysticercosis can be as high 1 per
1000 population and may account for up to 20% of
neurological case in some countries (e.g., Mexico);
cysticercosis ocular involvement occurs in about 2.5% of
patients and muscular involvement is as high as 10%
(India).
Cysticercus on the
eyeground
subcutaneous
nodules
pseudohypertrophy of muscle
Cysticerci in brain
Cysticerci in heart
Cysticerci in tongue
DIAGNOSIS
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For adult worm infection (Teaniasis)
* History of eating raw pork
* Find gravid proglottids in feces
* Perianal swab to find eggs
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For cysticercosis
* Specific diagnosis is difficult to establish, the
history and adult worm infection attribute to
strong suspicion
* Biopsy to subcutaneous lesions
* Computerized axial tomography or magnetic
resonance imaging
* Serological examination for specific antibody
Epidemiological distribution
World-wide distribution.
Epidemic in central and south America (Mexico), Africa,
South-east Asia, eastern Europe, Micronesia .
High prevenlence
Medium prevelence
Low or no prevelence
Epidemic limited area
Data unavialable
PRINCIPLES OF CONTROL
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Treat all patients to eradicate the source of larvae
parasitism
Pumpkin seed and areca nut ;
Praziquantel
Avoid the fecal contamination of pig feed
Modernization of raising pigs
Pay attention to personal and food hygiene
Intensive examination of the pork
Adequate cooking or freezing of meat are effective
precautions
 cysticerci do not survive at temperatures below -10℃ and
above 50 ℃.
Customs of pig husbandry
Teania saginata
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Can be up to 4 to 8 meters long
The scolex with four suckers
The gravid proglottids with a 15-30 branched uterus
The eggs of T. solium and T. saginata are
indistinguishable
gravid proglottid of T. solium
gravid proglottid of T. saginata
LIFE CYCLE
LIFE CYCLE
Human is the only definitive host, cattle is
the intermediate host
 Adult worm reside in the lumen of the upper
part small intestine
 The infective stage to man is larva
 No cysticercus in human
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PATHOGENESIS
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The adult parasite induces some host reaction
The process of calcification may be accompanied
by the release of antigens -- inflammatory
reaction
DIAGNOSIS
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For adult worm infection
Find gravid proglottids in feces or
experimental inducing worm
DISTRIBUTION
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T.saginata is prevalent in regions where
cattle are raised: Africa, Middle-East,
Central and South America, Europe and
Asia.
PRINCIPLES OF CONTROL
Treat the patients --Pumpkin seed and
areca nut; Praziquantel
 Modernization of raising cattle
 Intensive examination of the beef
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COMPARISON OF THE TWO TAPEWORMS
T. solium
T. saginata
Size
2-4m
4-8m
Scolex
Rostellum & hooks
No
Mature Proglottid
3 lobes of ovary
2 lobes of ovary
Gravid proglottid
Uterine Branches<13
>15
Intermediate Host
Swine & Human
Cattle
Disease caused
Taeniasis & cysticercosis
Taeniasis only
Infective stage
Egg & Cysticercus
Cysticercus Only
Mode of infection
Cross or autoinfection
Cross only
Diagnosis
Egg may be found in stool
Perianal egg exam
Clinical significance
Much more important
Less than T. solium
Chemotherapy
Should be instant
Not so urgent