Appearance and Morphology
Parasite and Appearance
Morphology
 Causative agent of taeniasis or beef tapeworm
infection
 Humans are the only definitive hosts
 Adult worm is 4 to 6 meters long
 Each worm may have 1,000 to 2,000 proglottids
 Mature segment has bilobed ovary and multiple
testes
 Gravid proglotttids are longer than wide (16 –
20 mm by 5 to 7 mm.)
 Scolex is cuboidal with 4 prominent suckers or
acetabula
 Scolex has no hooks or rostellum
 Gravid uterus may contain as many as 100,000
eggs
Taenia saginata (Beef Tapeworm)
Scolex
Gravid Proglottid
Taenia solium (Pork Tapeworm)
Gravid proglottid
Scolex with rostellum
Hymenolepi s nana (Dwarf Tapeworm)
 Causative agent of taeniasis or pork tapeworm
infection
 Humans are the only definitive host but can
become an intermediate host
 Adult worm is 2 – 4 meters in length
 May contain 800 – 2000 proglottids
 Each gravid proglottid may contain 30,000 to
50,000 eggs
 Globular scolex with 4 cup-shaped suckers and
a rostellium with double crown (hooklets)
 Mature segment has trilobed ovary; testes lesser
than T. saginata
 Eggs of Taenia cannot be differentiated
 Life may be up to 25 years
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Scolex with retractile
rostellum
Gravid proglottids
Causative agent of dwarf tapeworm infection
Short worm: 20 mm. long
May have as many as 200 proglottids
Small globular scolex bears short retractile
rostellium with a single ring of hooklets and 4
cup-shaped suckers
Mature proglottids are ellipsoidal, about 4 times
as broad as long
Gravid segments contain sac-like uteri which
may contain 80-100 eggs each.
Hymenolepis diminuta (Rat Tapeworm)
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Scolex
Causative agent of rat tapeworm infection
Adult worm is 10 to 60 cm long
It may have 800 to 1000 proglottids
Club-shaped scolex has rudimentary unarmed
rostellum and four small suckers
Proglottids resemble that of H. nana
Gravid proglottids have sac-like uteri
Proglottids
Echinococcus granulosus (Hydatid Tapeworm or Dog
Tapeworm)
Globular scolex with
prominent rostellum
Adult
Dipylidium caninum (Pumpkin Seed Tapeworm)
 Causative agent of echinococcosis, hydatid
disease or hydatid cyst
 Dogs and other canines are the most common
definitive hosts
 Herbivores are intermediate hosts
 Has become a common zoonotic infection
 Humans become accidental intermediate hosts
and dead end host
 Smallest tapeworm of medical importance
 Globular scolex with prominent rostellum
armed with 2 rows of 30 – 36 hooks
 Four prominent suckers
 Body of an adult has 3 proglottids (immature,
mature, and gravid)
 Gravid proglottid has median uterus with 12 –
15 branches
 Uterus may contain up to 500 eggs
 Eggs resemble that of the Taenia
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Scolex
Gravid Segment
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Causative agent of dipylidiasis or dog or cat
tapeworm infection
Causes tapeworm infection in dogs and cats
Humans are accidental hosts
Scolex is globular with rostellum containing 1 –
7 rows of rosethorn shaped hooklets and 4
deeply cup-shaped suckers
Gravid proglottids resemble pumpkin seeds
15 to 70 cm. in length
60 to 175 proglottids per worm
Eggs are packed in egg capsule containing 15 to
25 eggs
Each egg contains an oncosphere with six
hooklets
Diphyllobothrium latum (Broad Fish Tapeworm)
Scolex with
suctorial groves
Spirometra
 Causative agent of Diphyllobothriasis or fish
tapeworm disease
 Humans are the definitive host
 Ivory or grayish-yellow in color
 Length ranges from 3 to 10 meters
 Each worm may have more than 3,000
proglotttids.
 proglotttids are broader than long
 The scolex is small and almond-shaped with 2
suctorial groves called bothria
 Life span may reach up to 20 years
 The uterus in each segment is coiled and
rosette-like
Rosette-like uteri
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Echinococcus multilocularis
Caused by the presence of plerocercoid larvae
or sparganum of the Genus Spirometra in
humans
Spirometra resembles D. latum but are smaller
S. mansoni, S. erinacei, and S. ranarum
commonly infect humans
Life cycle has the same pattern with D. latum
Dogs, cats and wild carnivores are definitive
hosts
Cyclops or copepods are primary intermediate
hosts
Rodents, frogs and snakes are secondary
intermediate hosts
More than 6 cases have been reported in the
Philippines
 Foxes, wolves and cats are definitive hosts
 Rodents are intermediate hosts
 Humans become intermediate and dead end
host after contact with soil or ingestion of raw
vegetation contaminated with feces of definitive
hosts
 Ingested eggs release oncosphere which
develop into cyst
 Cyst is multilocular or multicelled
 Encystation usually occurs in the liver
 Cysts usually do not complete normal
development
 Protoscolices do not develop
Eggs and larvae
Egg and larvae
Parasite
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T. saginata &
T. solium
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Yellowish brown
Spherical or subspherical in shape
Consists of a thick covering called the
embryophore
Embryophore is striated
The embryo or the oncosphere is enclosed
within the embryophore
Three pairs of hooklets can be seen in the
embryo
Eggs cannot be distinguished from Taenia
solium
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Yellowish-brown in color
55-76 µ by 41-56 µ in size
Single-shelled
Has an inconspicuous operculum at one end
and a knob-like thickening at the other end
H. nana
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Oval or globular in shape
Two membranes enclose the embryo
Inner membrane has two polar thickenings,
from each of which 4 to 8 polar filaments
arise
H. diminuta
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Almost resembles H. nana egg
Slightly bigger than H. nana
There are no polar filaments in the inner
membrane
D. latum
Appearance
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D. caninum
E. granulosus
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Passed out in the feces along with the
proglottids
Released by contraction of proglottids or
disintegration outside the host
Spherical
Thin shelled
With a hexacanth embryo
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Ovoid in shape
Resemble Taenia ova
Hexacanth embryo with 3 pairs of hooks
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Parasite
Life Cycle
Diphyllobothrium latum
intermediate hosts
Primary
• Freshwater copepods
• Cyclops
• Diaptomus
Secondary
• Trout
• Salmon
• Pike
• Perch
• Whitefish
• Turbot
Taenia saginata
Taenia solium
 Gravid proglottids of adult in the intestines of host separate from strobila
(groups of 5 or 6)
 Proglottids rupture before or after leaving the host releasing the eggs
 Eggs are ingested by hogs or wild boars thru contaminated food or water
 Embryophore is digested and oncosphere is released, penetrate the intestinal
mucosa and enter the lymph or blood circulation
 Oncosphere reaches the muscles and visceral organs and encyst forming the
larval form cysticercus cellulosae
 Humans become definitive hosts upon ingestion of improperly cooked
infected meat
 Larva is liberated from the cyst and scolex attaches to the intestinal mucosa
 Maturity is achieved in about 12 weeks
Hymenolepis nana
Hymenolepis diminuta
Dipylidium caninum
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Echinococcus granulosus
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Parasite
D. latum
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T. saginata
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T. solium
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Adult worms inhabit the small intestines of definitive hosts
Eggs from proglottids may be released inside or outside of the host
Herbivores become intermediate hosts upon ingestion of contaminated
vegetation
Humans may also become intermediate dead end hosts
Oncospheres are released, penetrate the intestinal wall and are carried to the
bloodstream
Oncospheres are carried by the blood to the different parts of the body where
they form the larval stage called hydatid cyst
Canines become definitive hosts upon ingestion of animal organs containing
the cyst
Protoscolices within the cyst envaginate, attach to the small instestines and
become adults
Pathogenesis and Symptoms
Infection is usually limited to a single worm
Large number of worms are rarely involved and cause intestinal obstruction
Infected individuals may show no signs of infection
Worm attached to the upper jejunum compete with the host for vitamin B12 resulting in
anemia similar to pernicious anemia
Nervous disturbances, digestive disorders, abdominal discomfort, weight loss and
weakness may be experienced
Usually involves single worm infection
6 – 28 worms in a single patient were reported
No significant clinical manifestation
Complaints due to highly motile proglottids
Proglottids may cause obstruction in the biliary duct and may enter the appendix
Passing out of proglottids, or even the strobila, is very common
Cysticercosis
Humans can harbor the larval stage of T. solium
Humans ingest T. solium eggs from contaminated food or water
May also be a result of autoinfection due to poor hygenic practices
Oncosphere will penetrate the intestinal mucosa, enter the circulation and encyst in
various tissues (Cysticercus cellulosae)
Symptoms depends upon intensity, size, and location
Most serious manifestation involves cerebral cysticercosis or neurocysticercosis (NCC)
NCC is considered one of the most serious zoonotic disease in the world.
Convulsions/epileptic seizures are common manifestations of NCC and may be
accompanied by focal motor, sensory and mental changes
Mental disorders depend upon the site and intensity of infection
Cyst remain in the tissue for up to 5 years producing inflammatory response
Cyst is calcified upon the death of the larva
Intestinal Infection
Mild nonspecific abdominal complaints
proglotttids of T. solium are not as active as T. saginata
No anemia in pork tapeworm infection
H. nana
H. diminuta
D. caninum
E. granulosus
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E. multilocularis
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Spirometra
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No significant damage to the intestinal mucosa
Heavy infection may lead to enteritis
No symptoms or only vague abdominal pain for light infection
Children may experience lack of appetite, anorexia, vomiting and dizziness
Autoinfection can occur
Cercocystis cyst in intestinal villus
Asymptomatic
Mild abdominal pain
Gastrointestinal complaints
Infected individuals are usually asymptomatic
Symptoms if present are minimal
Multiple worm infection is rare
Presence of actively motile proglottids in the feces are usually observed
Dependent upon the location of the cyst
Distribution of cyst in humans
Liver and peritoneal cavity: 66%
Lungs:
22%
Kidney:
3%
Bone: 2%
Brain: 1%
Other tissues: 6%
Damage to the tissue resulting from pressure caused by the enlargement of the cyst
Cyst may rupture in the tissue releasing protoscolices and resulting in formation of
secondary cysts in other organs (autoinfection)
Hydatid cyst
Usually 1 – 7 cm. in diameter (may reach 20 cm.)
Generally spherical in human hosts
E. granulosus cyst is unilocular or one celled
Composed of 6 parts/ layers
• External elastic non-nucleated hyaline cuticle secreted by the second layer (semipermeable)
• Inner nucleated germinal layer
• Colorless or light yellow hydatid fluid
• Brood capsules containing protoscolices
• Daughter cyst which resembles the mother cyst
“Hydatid sand” refers to protoscolices that are not enclosed in brood capsules
Ingested eggs release oncosphere which develop into cyst
Cyst is multilocular or multicelled
Encystation usually occurs in the liver
Cysts usually do not complete normal development
Protoscolices do not develop
Larva may migrate to any part of the body
Eyes, subcutaneous tissues, muscles of the thorax, thighs, abdomen, and inguinal regions
are commonly affected
Elongation and contraction of larvae cause inflammatory and painful edema
Degeneration of larva causes local inflammation and tissue necrosis
Periodic giant urticaria, local indurations, edema and erythema may appear accompanied
by chills, fevers and high eosinophilia
Parasite
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D. latum
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T. saginata
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T. solium
H. nana
H. diminuta
D. caninum
E. granulosus
E. multilocularis
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Diagnosis
History of travel to endemic areas accompanied
by a raw fish diet and pernicious type anemia is
suggestive
Finding the characteristic eggs in the stool
through DFS or Kato technique
Examination of the gastric juice to differentiate
between diphyllobothriasis anemia and pernicious
anemia
Achlorhydria accompanies pernicious anemia
Identification of the gravid proglottids or the eggs
Eggs are usually collected thru scotch tape (swab)
method
Gravid proglottids may be seen in beddings and
undergarments
Counting the uterine branches in a proglottids is
useful in differentiating T. saginata from T.
solium
Segment is pressed between two slides and
examined under microscope (may be stained)
15 to 30 uterine branches for T. saginata as to 7 to
15 branches for T. solium
Identification of characteristic gravid proglottids
in the feces and eggs in the perianal region
Eggs cannot be differentiated from T. saginata
Examination of gravid proglottids is used for
specific diagnosis
NCC Diagnosis
Sudden convulsions and epileptic seizures in
teenagers and adults not associated with other
brain dysfunctions
Patient’s location, travel history, feeding habit
Biopsy
CT scan and MRI
ELISA and Western Blot
Finding of the characteristic eggs in the stool
Finding the characteristic eggs in the feces
 Pertinent patient information
 Residence in endemic area
 Close contact with definitive host
 Finding protoscolices, brood capsules or daughter
cyst in the hydatid cyst after surgery
 Serological tests
 Enzyme Linked Immunosorbent Assay
(ELISA)
 Indirect Hemagglutination (IHA)
 Indirect Fluorescence Antibody (IFA)
 CT scan and ultrasound may reveal the cyst
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Treatment
Praziquantel is the drug of
choice
Make sure that the scolex is
expelled
Niclosamide is also effective
but it produces digested worms
Re-examine the stool after 3
months if scolex was not seen
 Praziquantel is the drug of
choice
 Make sure that the scolex is
expelled
 Niclosamide is also effective
but it produces digested worms
 Recovery of the scolex
 No infection after three months
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Same as T. saginata and D.
latum for intestinal infection
Recovery of scolex and
negative stool exam in 3 months
Praziquantel at 50 – 75 mg/kg
for 30 days for NCC
Steroids are given to relieve
inflammatory response
Ocular cysticercosis can be
treated surgically
Praziquantel and Niclosamide
Praziquantel and Niclosamide
Same as other tapeworms
Surgery
Rupture of the cyst should be
avoided during surgery
Enucleation is usually done
Removal of the hydatid fluid
and replacing it with chemicals
that destroy the daughter cells
and protoscolices before
removal
Chemotherapy with albendazole
Cyclosporin A
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Spirometra
Parasite
Finding the larva in lesions
Feeding experiments to animals is necessary to
identify the species.
Mode of Transmission
Surgical removal of the larva is the
only treatment
Epidemiology
Prevention and Control
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D. latum
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T. saginata
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T. solium
Very common in places
where people eat raw or
poorly cooked beef
Poor sanitation and
flooded pastures along
rivers
Raw sewage disposed
disposed in the river
Use of nightsoil
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Common in places
where hogs and humans
have access to human
feces
Lack of sanitation
Human feces are fed to
hogs
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H. nana
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H. diminuta
Direct hand to mouth
Rarely thru
contaminated food
and water
Eggs are easily
dessicated
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Proper human fecal
disposal
Avoidance of eating raw or
undercooked fish
Thorough cooking of fish
before consumption
Cysticercus bovis in cattle
meat may be destroyed by:
freezing (-10°C) for 5 days
Heating above 57°C
(thermal death point)
Soaking in 25% salt
solution for 5 days
Control source of infection
Avoid soil contamination
Proper meat inspection
Cysticercus bovis in cattle
meat may be destroyed by:
freezing (-10°C) for 5 days
Heating above 57°C
(thermal death point)
Soaking in 25% salt
solution for 5 days
Control source of infection
Avoid soil contamination
Proper meat inspection
Freezing meat at (-20°C)
for 10 days kills the cyst
Treatment of infected
persons
Improving hygienic
practices of children
Sanitation
Rodent control
Control of infected
individuals
Control of intermediate
hosts
Rodent control
Control of insect
droppings
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D. caninum
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E. granulosus
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Accidental ingestion
of infected dog or cat
fleas or lice
Ingestion may be thru
contaminated food or
hand to mouth
Children are more
susceptible
High percentage of
dogs are infected
Hand to mouth after
contact with
contaminated soil
Hand to mouth after
contact with fur of
infected dog
Infected dog licking
the face of humans
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E.
multilocularis
Spirometra
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Humans acquire the
infection thru:
Ingestion of water
contaminated with
the infected primary
intermediate host
Consuming frogs,
snakes or rodents
harboring the
plerocercoid larva or
sparganum
Use of infected frogs
and snakes as
poultice (plerocercoid
larva or sparganum
penetrate the
cutaneous tissue)
Common in places
where dogs are fed with
fresh meat or animal
viscera
Dog owners from
endemic areas are highly
susceptible
High incidence in places
where close contact with
pets is practiced
Eggs remain alive in soil
that is moist and shaded
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Deworming and flea
control of pets
Avoid close contact with
pets especially if the pet is
flea infested
Eradication of parasite in
natural intermediate and
definitive hosts
Dogs should not be fed
uncooked animal parts
Control of stray dogs
Personal hygiene