Phylum: Platyhelminthes (Flatworms)
1-Cestoda (tape worms).
2-Trematoda (flukes).
Cestoda (tape worms)
A) Intestinal adult tapeworms.
B) Extra-intestinal larval tapeworms.
Class: Cestoda (Tape worm)
1- The length of the different species varies from 3mm to 10 meters.
2- Segmented body: The body of the typical cestode consists of 3 distinct
regions: scolex, neck, and strobila
3- Scolex (head) provided with suckers, sometime hooks.
4- Hermaphroditic mature segment has male and female reproductive system
5- Despite the lack of a digestive system (no mouth, no gut, no anus) they
do absorb food from the hosts intestine
1- The size 3mm – 10 m.
General Morphology
• The body of the typical cestode consists of 3 distinct regions:
• scolex
• neck
• strobila
Form and Function: The Scolex cont.
• The scolices of tapeworms are typically categorized as either acetabulate or bothriate,
depending on the type of sucker present
• An acetabulate scolex is characterized by the presence of 4 muscular cups sunk into
the equatorial surface of the scolex; cups are radially arranged equidistant from each
other
In addition to muscular cups, there may be accessory •
holdfast structures, such as hooks to help anchor the
scolex to the host’s intestinal wall
In this case, the scolex is called an armed scolex•
These hooks are usually grouped at the apical end of •
the scolex on a protrusible rostellum
rostellum
Scolex:
is located at the anterior end and functions as an attachment
structure
 4 suckers
 hooklets: These hooks are usually grouped at the apical end
of the scolex on a protrusible rostellum
Neck
• The neck is an unsegmented, poorly differentiated region
immediately posterior to the scolex
• short measuring 5 to 10 mm in length
The Strobila
• As new proglottids are formed from the neck region, they
push the older ones progressively posteriad, creating a chain of
proglottids - the strobila
• The asexual process of forming segments is termed
strobilation.
The stroblia can be loosely subdivided into 3 regions:
 Immature
 Mature
 Gravid proglottids
mature segment contain
testes and ovary
gravid proglottid
has a median uterus filled with eggs (50 – 80 000)
Larval (metacestoda):
1- The larval are extracellular parasites, visible to the
naked eye, seen as bladders with an scolex.
2- The external surface is a tegumentary tissue, similar
to that found in the adult worm.
3- In human infection, these larvae can survive for a
many years.
4- Dead parasite tissue, leaving a calcified in both
muscle and brain tissue.
Classification of Cestoda
Intestinal adult tapeworms.
Taenia solium
Taenia saginata
Taenia multicepsis
Hymenolepis nana
Hymenolepis diminuta
Dipylidium caninum
Diphyllobothrium latum
Extra-intestinal larval tapeworms
Echinococcus granulosus
Echinococcus multilocularis
Taenia solium (pork Tapeworm)
Taenia solium
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Common name: The Pork Tapeworm.
Habitat: Small intestine.
Route of infection: Eating of unwell cooked Pork meat.
Definitive host : Human.
Intermediate host: Pork, Human (occasional).
Infective stage: Cysticercus larvae (Pork).
Diagnostic stage: Eggs or gravid in Feces.
Disease: Adults cause: Taeniasis.
Larvae cause: Cysticercosis( presences of
Cysticercus larvae in brain and muscles.
Taenia solium
Adult worm
1- 2-4 meters in length)
2- Head or scolex
globular in shaped with 4 suckers
rounded rostellum armed with
double rows of large and small hooks
numbering 22 to 36.
3- Neck
short measuring 5 to 10 mm in length.
Proglottids
 Numbers : 700 to 1000 proglottids
Composed of:
1- Immature proglottid
2- Mature proglottid: nearly square containing full set
of functioning male and female reproductive organs
3- Gravid proglottid
 longer than broader consists:
 gravid uterus with 3 to 13 lateral uterine branches
arranged.
Mature proglottid
Gravid proglottid
Egg
 Shape – spherical
 Size: 30-40 um in diameter
 radially-striated shells
 Outer shell – thin and rarely seen
 Inner shell brown, thick and striated
 embryo or oncosphere with six hooklets
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 Larval stage or bladder worm
 also called Cysticercus cellulosae
 measurement – 5 to 10 mm in length and
5 mm in diameter
 scolex
 hooks
 suckers.
EPIDEMIOLOGY
T. solium infection
 Human infected (raw or undercooked pork)
 Man is the only definitive host and the pig
appears to be the only intermediate host
Man become the intermediate host Can be caused by:
 ingestion of eggs from contaminated food or water
 by internal autoinfection when the eggs are carried by
reverse peristalsis back to the duodenum or stomach
Pathology
1- By adult in lumen of the small intestines :
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intestinal obstruction
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abdominal pain
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Vomiting .
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nausea
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weight loss and diarrhea.
2- By larval stage (cysticercus) Symptoms depend on
location and number of larva, which encyst in the
muscle and other tissues :
a. cellular reactions
b. fibrosis
c. necrosis
 cysticercosis in the brain may cause:
a. epilepsy
b. meningitis, and encephalitis
 Eye – cause blindness
Symptoms depend on location and number of larva
Diagnosis:
1-Adult worms:
Taenia infections are diagnosis by finding gravid segments in
the feces, because their eggs are identical.
2- Cysticercosis:
A- Serologic tests ELISA.
B- X-rays may reveal calcified cysticerci.
C- CT scan can show living cysticerci.
Taenia saginata
Beef Tapeworm.
Taenia saginata
 Common name: The Beef Tapeworm.
 Habitat: Small intestine.
 infection: Eating of unwell cooked cow meat.
 Definitive host : Human.
 Intermediate host: Cows also other herbivores.
 Infective stage: Cysticercus larvae.
 Diagnostic stage: Eggs and gravid in Feces.
 Disease: Adults cause Taeniasis.
Taenia solium
Intermediate host:
Length :
No. proglottids:
Scolex :
Pig
2-4 m
700-1000
4 suckers
with hooklets
Taenia saginata
cattle
4-8 m
1000-2000
4 suckers but
no hooklets
Taenia solium
Gravid proglottid:
3-13 branches
Taenia saginata
13-30 branches
Larval stage (Cysticercus)
Taenia solium
(Cysticercus cellulose)
Scolex with hooklets
found in pig and man
Taenia saginata
(Cysticercus bovis)
no hooklets on Scolex
only found in cattle
Echinococcus granulosus
Dog tape worm
Echinococcus granulosus
Dog tape worm
 Habitat: adult: Small intestine in Dogs
Larvae (Hydatid cyst): in Liver, Lung, brain in
Intermediate host
 Definitive host : Dogs and other canines.
 Intermediate host: Sheep, cattle, etc, and other herbivores.
Accidentally Human.
 Disease: Unilocular Hydatid disease.
Morphology:
 3-8 mm in length.
 Scolex with Four suckers.
 Neck.
 Immature segment.
 Mature segment.
 Gravid segment.
Ova:
 Shape Round to Oval
 Embryonated ( Hexacanth embryo inside)
 Radially striated egg shell.
 Onchosphere: six-hooked embryo inside the egg.
Hydatid cysts in the Liver
Hydatid Cyst:
• At maturity, the cyst wall contains 2 layers:
1- laminated, noncellular outer tegument called the ectocyst,
2- inner, germinal epithelium that produces the protoscolices called the endocyst
• Brood capsules attached to the germinal epithelium by the stalk, extend into the
fluid filled cavity of the cyst
•Each brood capsule contains 10-30 protoscolices
• If a cyst ruptures within a host, each liberated protoscolex can produce a
daughter cyst
Protoscolices(hydatid sand)
From hydatid cyst
Types of Hydatid Cyst
1-Sterile cyst
2- Fertile cyst
Pathology:
Some people may have cysts in their bodies 5-20 years
without experiencing symptoms, or may never
experience symptoms.
A. Mechanical
1. Growing hydatid cyst lodged in the vital organs like
liver, lungs, brain, heart interferes with the functions of
the organs
2. Infection may become fatal due to growing cyst which
can cause obstruction to the organ
B. Toxic
Rupture of the cyst may produce allergic.
A hydatid cyst in the cranium
of a child (the ruler at the top
measures 6 inches long, and the
child's brain is below the
hydatid cyst). This infection
resulted in the child's death.
A figure showing a surgery procedure to remove
hydatid cyst from a human patient
Diagnosis:
The diagnosis of Hydatidosis relies mainly on finding
cysts by:
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CT scan,
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X- Ray
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Serological tests.
Treatment:
 Surgery is the most common form of treatment for
Hydatid cysts. After surgery, medication may be
necessary to keep the cyst from recurring.
 The drug of choice is
 Albendazole, mebendazol
Prevention and Control
1- Personal hygiene
2- Prevent dogs from eating carcasses of sheep, goat
cattle,etc.
3- c0ntrol of stray dogs.
Hymenolepis nana
dwarf tapeworm
Hymenolepis nana
 Common name: The Dwarf-Tape-Worm, ---Nanos = dwarf
 Disease: Hymenolepiasis.
 Habitat: Small intestine
 Definitive host: Human, Mice,Rats
 Infective stage:
1- Eggs ( if it eaten directly by Definitive host).
2-Cysticercoid larvae from insects.
 Diagnostic stage: Eggs in feces.
Hosts:
 Definitive host
 Human
 Mice
 Rats
The only cestode that
parasitizes humans
without requiring an
intermediate host.
Intermediate host (Optional):
Fleas, Beetles
Morphology:
 Adult worm 1-4.5 cm long and 0.5-1 mm wide
 Neck is long and slender
 They have 100-200 segments that are wider then they
are long
 Scolex also has four suckers and, rostellum armed with
a single circle of 20-30 hooks
 proglottids are much broader than long
 Male system has 3 spherical testes, and female
bi-lobed ovary
Hymenolepis nana adult:
Egg:
 Eggs generally measure between 30 to 47
microns in diameter.
 They are round to oval, and should contain a
six-hooked oncosphere.
 They have polar filaments that lie between
the eggshell and the oncosphere.
polar filaments
Hymenolepis nana life cycle2
Pathology and Clinical disease:
Most cases are asymptomatic, but with heavy infection they
may be:
1- abdominal pain, nausea, vomiting, diarrhea, and anemia.
2- nervous symptoms, including dizziness and irritability, can
occur in children.
Diagnosis:
Ova found in the feces
polar filaments