Cestodes, or tapeworms, are flat segmented parasitic worms that infect the intestines of humans and other animals. They range in size from a few millimeters to several meters in length. The body consists of a head (scolex) and chain of segments (proglottids) that contain reproductive organs. Two major orders that infect humans are Pseudophyllidea and Cyclophyllidea. Pseudophyllidea have slit-like grooves instead of suckers, while Cyclophyllidea have cup-like suckers. Common tapeworms infecting humans include Diphyllobothrium latum (fish tapeworm), Taenia saginata (beef tapeworm), Taenia sol

1. CESTODES

2. General Characteristics
Majority are long, segmented and tape-like are called
tapeworms
Dorso-ventrally flattened
Size varies from a few mm to several meters
Adult worms are found in the intestinal canal of man and
animals
“head” or scolex is provided with suckers and sometimes
with hooks that serve as organs of attachment
There are 3 regions in an adult worm:
Head: scolex
Neck
Strobila (body or trunk)
Consist of a series of segment called proglottids

3. General Characteristics
Sexes are not separate
Body cavity is absent
Alimentary canal is entirely absent
Excretory and nervous systems are present
Reproductive system is present and complete in each
segment
According to maturity of reproductive organs, three types of
segments of the strobila can be recognized from the fron backwards
Immature: male and female organs are not differentiated
Mature: male and female organs have become differentiated
(male organs appear first)
Gravid: uteri are filled with eggs (other organs are atrophied or
have disappeared)

4. Classification of Cestodes
Infecting Man
I. Pseudophyllidean cestodes
Possess false or slit-like grooves called bothria
Adult worms in Intestine
Diphyllobothrium latum: Fish Tapeworm
Larval stages: Plerocercoid in Man
Sparganum mansoni
Sparganum proliferum

5. Classification of Cestodes
Infecting Man
II. Cyclophyllidean cestodes
Possess cup-like and round suckers called
acetabula
Adult Worms in the Intestine
Taenia saginata
Taenia solium
Hymenolepis nana
Hymenolepis diminuta
Dipylidium caninum

6. Classification of Cestodes
Infecting Man
According to Habitat
II. Cyclophyllidean cestodes
Possess cup-like and round suckers called
acetabula
Larval Stages in Man
Hydatid cyst of Echinococcus granulosus and
Echinococcus multilocularis
Cysticercus cellulosa of Taenia solium
Coenurus cerebralis of Multiceps multiceps
Coenurus glomeratus of Multiceps glomeratus

7. Differences Between a Pseudophyllidean
and a Cyclophyllidean Cestode
Pseudophyllidean Cyclophyllidean
Head or scolex Bears 2 slit-like Bears 4cup-like
grooves suckers
uterus No branching Branching
Convoluted uterine May or may not be
tubes assume the present
form of rosettes
Uterine pore present absent
Common genital pore Ventral; in the midline lateral
eggs Operculated; gives Not operculated; do
rise to ciliated larvae not give rise to ciliated
larvae

8. Order Pseudophyllidea
Characteristics
Large worms consisting of a long chain of segments
“head” has two slit-like sucking grooves called bothria
instead of suckers
Uterine glands are widely scattered in the parenchyma
and is composed of many acini
Genital pores are on the ventral surface of the segment
and are not marginal
Uterus opens to the exterior through which eggs come
out
Eggs are operculated and can develop only in water;
immature when oviposited and oncosphere gives rise to
ciliated embryo
Larval development proceeds in two intermediate hosts:
First larval stage is called procercoid
Second larval stage is called plerocercoid

9. Diphyllobothrium latum
Common Name:
Fish Tapeworm
Broad Tapeworm
Morphology
Adult worm is yellowish
grey in color
Dark central markings
in the strobila are due
to the egg-filled uterus
Measures 3 to 10
meters in length
Life-span is for a period
of 5 to 15 years
http://www.revistaaquatic.com/aquatic/html/art1401/fig11.gif 3-01-08

10. Diphyllobothrium latum
Scolex is spoon-shaped
or spatulate
Scolex bears 2 slit-like
grooves called bothria
(1 on the dorsal surface
and 1 on the ventral
surface)
Scolex has no rostellum
and no hooklets
Neck is thin and
unsegmented and is
much longer than the
head

11. Diphyllobothrium latum
Morphology
3,000 to 4,000
A mature segment is filled
with male and female
reproductive organs
Terminal segments shrink
and becomes empty as
eggs are constantly
discharged
Dried up segments break
off from the body in chains
and are passed out in the
host’s feces
Uterus at the center of the
segment appears in the
form of a rosette

12. Diphyllobothrium latum
http://pathmicro.med.sc.edu/parasitology/dip1.jpg 3-01-08

13. Diphyllobothrium latum
Ova
Passed out in the host’s
feces in large numbers
Oval
Bile stained
Contains abundant
granules and
unsegmented ovum
Inconspicuous operculum
at one end and a small
knob at the other end
Does not float in saturated
solutions of common salt
A single egg gives rise to
a single larva
Not infective to man
http://workforce.cup.edu/Buckelew/images/Diphyllobothrium%20latum%20egg.jpg 3-01-08

14. Diphyllobothrium latum
larva
Passed first in water and then in the respective intermediate
hosts
3 stage
– First stage larva
Coracidium
Ciliated oncosphere that develops from egg in water
– Second stage larva
Procercoid
Spindle-like solid body with cephalic invagination
Found inside the cyclops (the first intermediate host)
– Third stage larva
Plerocercoid
Head is invaginated in the neck
Found in the fresh water fish, the second intermediate host

15. Diphyllobothrium latum

16. Diphyllobothrium latum

17. Diphyllobothrium latum
Final Host
Man, dog, cat
Small intestine
1st I.H.
Cyclops or Diaptomus
2nd I.H.
Fresh water fish, pike, trout, salmon, perch
Mode of Infection
Ingestion of imperfectly cooked infected fish or roe containing
plerocercoid larvae
Infection
Diphyllobothriasis
G.I. disturbances and anemia
Diagnosis
Microscopic examination of feces for the characteristic
operculated eggs

18. Order Cyclophyllidea
Characteristics
Large or small worms consisting of chains of segments
Scolex is quadrate with four cup-like round suckers
An apical rostellum with hooklets may be present
Vitelline glands concentrated in a single mass
Common genital pore is marginal (on lateral side of
segment)
No uterine opening for the exit of eggs from the gravid
uterus
Eggs only escape from the rupture or disintegration of
ripe segments
Eggs are not operculated and can develop only in the
intermediate host, fully embryonated
Oncosphere is never a ciliated embryo
Larval development proceeds in one intermediate host

19. Taenia saginata
Beef Tapeworm
Unarmed Tapeworm
of Man
Adult worms are white
and semi-transparent
Measures about 5-10
meters or sometimes
up to 24 meters
Live up to 10 years or
more

20. Taenia saginata
1,000 to 2,000 proglottids
Common genital pore is marginally
situated
Vagina is provided with a
sphincter muscle
Gravid proglottid consists of a
uterus and a central longitudinal
stem with 15 – 30 branches on
each side
Highly branched proglottids
Gravid proglottid contains 97,000
to 124,000 ova
Gravid segments are expelled
singly and force their way through
the anal sphincter
Free gravid proglottid crawls out of
the anal orifice and oviposits on
the perianal skin

21. Taenia saginata

22. Taenia saginata
Ova
Liberated by rupture of
ripe proglottids
No uterine opening
Spherical
Thin, outer transparent
shell
Inner embryophore is
brown, thick walled and
radially striated
Has an oncosphere with 3
pairs of hooklets
Does not float in saturated
salt solutions
Eggs are resistant and
remain viable for 8 weeks
Infective only to cattle

23. Taenia saginata
Final Host: Man
Intermediate Host: cattle, cow buffalo
Mode of Infection; eating beef containing Cysticercus
bovis
Pathogenesis
Taeniasis
Passage of proglottids in stool
Mild irritation at site of attachment
Epigastric pain
Hunger fangs
Weakness
Weight loss
Loss of appetite
Pruritis
Obstruction in intestine but also in bile and pancreatic ducts and
appendix because proglottids are actively motile

24. Taenia saginata
Diagnosis
Identifying characteristic eggs, proglottids or scolex
Usual specimen is gravid proglottids ( lateral
branches 15-20)
Concentration techniques for eggs (eggs rarely
passed out in stool)
Perianal swabs
Treatment
Praziquantel
5-10mg/kg single dose
Criteria for cure
Recovery of the scolex
Negative stool examination 3 months after
treatment

25. Taenia solium
Pork Tape worm
Armed Tapeworm of Man
Taeniasis is common among
those eating raw or insufficiently
cooked “measly pork”
Uncommon among non-pork
eaters

26. Taenia solium
Scolex is globular in
outline with 4 circular
suckers
Scolex has a
rostellum armed with
a double row of
alternating large and
small hooklets
Rostellar hooklets are
shaped like daggers
or Arabian poniards

27. Taenia solium

28. Taenia solium

29. Taenia solium
Adult worms measure
2-3 meters
Adult worms live up to 25
years

30. Taenia solium
800-900 proglottids
Common genital pore is
marginal and thick lipped
Vaginal opening is not
guarded by a muscular
sphincter
Gravid segments are
expelled passively in
chains of 5-6 at a time
and not singly.
Gravid proglottids
contains approx. 30,000
to 50,000 eggs

31. Taenia solium
Ova
– Same as those of
Taenia saginata
– Infective to man as
well as pigs
– Thick brown striated
embryophore
surrounding a
hexacanth embryo

32. Taenia solium
Final Host: Man
Intermediate Host: Pig
Mode of infection; eating measly pork
containing Cysticercus cellulosae
Diagnosis: stool examination for
proglottids/eggs

33. Taenia solium
Pathogenesis
Mild, non-specific abdominal complaints
Proglottids are not as motile as T. saginata so organ
obstruction is less likely.
Cysticercosis
Multiple
Develop in any organ or tissue
Neurocysticercosis (most serious zoonotic disease)
Chorioretinitis
vasculitis

34. Taenia solium
Diagnosis
Intestinal
Identifying the characteristic proglottids, eggs or scolex
Cysticercosis
Computed Axial Tomography
Magnetic Resonance Imaging
Treatment
Praziquantel: 5-10 mg/kg single dose for children and adults
Niclosamide not available locally
Criteria for cure:
Recovery of scolex
Negative stool exam 3 months after treatment

36. Comparison Between
T. saginata and T. solium
Taenia saginata Taenia solium
length 5-10 meters 2-5 meters
Head or scolex Large, quadrate, no Armed; with rostellum;
rostellum and hooks with hooklets
Number of proglottids 1,000 to 2,000 Below 1000
Expulsion Expelled singly and may Explelled passively in
be forced through the chains of 5 or 6
anal sphincter
uterus Highly branched with 15- Lateral branches 5-10 on
30 lateral branches on each side, thin, dendritic
each side; thin; and vaginal sphincter is
dichotomous absent
testes 300-400 follicles 150-200 follicles

37. Echinococcus granulosus
Taenia echinococcus
Dog Tapeworm
Hydatid Worm
Man harbors the larval form and not the
adult worms which however is found in the
intestine of dogs and canines

38. Echinococcus granulosus
Adult worms are small
(3-6 mm in length)
It is composed of a
Scolex
Neck
Strobila
3 segments
(occassionally 4)
Immature
Mature
Gravid

39. Echinococcus granulosus
Scolex bears 4
suckers and a
protrusible rostellum
with 2 circular rows of
hooks.

40. Echinococcus granulosus
Ova
Ovoid in shape
Resemble Taenia ova
Hexacanth embryo with
3 pairs of hooks
Infective to:
Man
Cattle
Sheep and other
herbivorous animals

41. Echinococcus granulosus
Larva
Found within the hydatid cyst developing inside the
intermediate host
Represents the structure of the scolex of the future
adult worm
Young larva are transformed into a hollow bladder
(hydatis , drop of water)
Brood capsules develop within the cysts and may
contain thousands of scolices
On entering the final host, the scolex armed with a
rostellum and 4 suckers become adult worms

42. Echinococcus granulosus

43. Echinococcus granulosus

44. Echinococcus granulosus
Definitive Host
Dog
Wolf
Fox
Jackal
Intermediate Host
Sheep
Pig
Cattle
Horse
Goat

45. Echinococcus granulosus
Definitive Host
Dog
Wolf
Fox
Jackal
Intermediate Host
Sheep
Pig
Cattle
Horse
Goat

46. Echinococcus granulosus
Pathogenesis
Echinococcosis
Pathology is caused by the developing larval cyst
in the intermediate host
Most common site of involvement is the liver
Echinococcus granulosus cyst: Unilocular hydatid
cyst
Echinococcus multilocularis: alveolar cyst
Some may be asymptomatic for years
Rupture of cyst in the lungs may present coughing
accompanied by allergic reactions

47. Echinococcus granulosus

48. Echinococcus granulosus
Encysted scolices of Echinococcus granulosus
in lung "hydatid sand"

49. Echinococcus granulosus
Encysted scolices of Echinococcus granulosus
in lung "hydatid sand"

50. Echinococcus granulosus
Encysted scolices of Echinococcus granulosus
in lung "hydatid sand"

51. Echinococcus granulosus
Diagnosis
Radiographic findings
Immunodiagnosis
Antibody detection
IHA
IFA
EIA
Antigen detection

52. Echinococcus granulosus
Treatment
Surgical resection: not 100% effective
Solicidal agent
Hibitane
95% ethanol
Hypertonic 30% Normal Saline Solution
PAIR technique for inoperable cyst
Puncture, Aspiration, Injection, Reaspiration
Intervention
Albendazole

53. Hymenolepis species
Genus is derived from the membranous character of the
egg shell “hymen”
3 testes in each mature segment
Uterus is sac-like and transverse
Eggs possess two membranes’ outer membrane is thin
and transparent
larval stage is called cysticercoid
Small bladder containing the invaginated head proximally
and a solid, elongted portion as a caudal appendage
There are 2 species;
Hymenolepis nana
Hymenolepis diminuta

54. Hymenolepis nana
Dwarf Tapeworm
Smallest tapeworm infecting man
Found worldwide
Mainly among children
Only human tapeworm that can complete its life
cycle in a single host
Man can harbor both the adult and larval stages
of the parasite
Exception to the general rule that
“Helminths do not multiply inside the body of
the definitive host”

55. Hymenolepis nana
Adult
Found in the ileum
Delicate strobila
25 mm to 45 mm
Worms may be presenr in
large numbers from 1,000
to 8,000
Short life span, about 2
weeks
Up to 200 proglottids
Transverse uterus
3 testes

56. Hymenolepis nana
Scolex
Subglobular
4 suckers
Provided with a
short retractile
rostellum armed
with a single row of
20-30 hooklets
Rostellar hooklets
are shaped like
tuning forks

57. Hymenolepis nana
Ova
Spherical or oval
Floats in saturated
solutions of common
salt
2 distinct membranes
Outer membrane is
thin transparent and
colorless
Inner embryophore
that encloses an
oncosphere with 3
pairs of lancet shaped
hooklets
Intermembranous
space is filled with
yolk granules and 4-8
polar filaments
emating from little
knobs at either end of
the embryophore

58. Hymenolepis nana

59. Hymenolepis nana
Mode of transmission is thru
Direct
Host ingests eggs that hatches in the duodenum
Indirect pathway
Accidental ingestion of infected arthropod
intermediate host like rice and flour beetles in
which cysticercoid arve are released nd develop
into adult worms in the small intestine of the host

60. Hymenolepis nana
Pathogenesis
Symptoms are produced due to patient’s immunological
response to the parasite
Asymptomatic for light worm burden
Headache
Dizziness
Anorexia
Pruritus of the nose and anus
Abdominal pain
Pallor
Desquamation of intestinal epithelial cell or as serious as
necrosis may occur
Regulatory immunity will eventually limit the
infection

61. Hymenolepis nana
Diagnosis
Demonstration of characteristic ova in the stool
Proglottids are not recovered because they
undergo degeneration prior to passage
Treatment
Praziquantel
– 25mg/kg single dose
– Drug dosage is higher than that of taeniasis
because of resistant cysticercoids in intestinal
tissue

62. Hymenolepis nana
Epidemiology
Countries with warm temperature
Southern USA
Latin America
Mediterranean
East Asia
Philippines

63. Hymenolepis diminuta
Rat tapeworm
Common parasite of rats and mice
Accidental human infections
Differs from Hymenolepis nana in morphology
and life cycle because it requires an
intermediate host
2 Hosts
Larval stage: cysticercoid is passed in fleas
Adult stage: in rats and mice and accidentally in humans
especially children who accidentally ingest infected fleas

64. Hymenolepis diminuta
Adult
Larger than
Hymenolepis nana
Measures 60 cm in
length

65. Hymenolepis diminuta
Scolex
Unarmed
rostellum
4 suckers

66. Hymenolepis diminuta

67. Hymenolepis diminuta
Proglottid
8,00 – 1,000
Mature proglottids of
Hymenolepis diminuta
from the laboratory rat.
The three spherical
bodies are testes which
surround the ovaries,
ootype and vitelline
glands. The genital
pores are on the left
margin

68. Hymenolepis diminuta
Ova
Larger than H.
nana
Outer shell is
yellowish in color
Inner
embryohore has
2 knob-like
thickenings
No polar
filaments

69. Hymenolepis diminuta
cysticercoid of Hymenolepis
diminuta.
The suffix indicates it is like a
cysticercus but this larva has
no bladder but instead has a
tail.
The dark body within the
spherical portion is the scolex.
The longer the tail, the more
mature the cysticercoid.
This stage is found inside an
insect such as the mealworm,

70. Hymenolepis diminuta

71. Hymenolepis diminuta
Pathogenesis
Hymenolepiasis
Worm burden in rodents is relatively
low
In man, highest worm burden is 19
Clinical manifestations are minimal
and non-specific

72. Hymenolepis diminuta
Treatment
Praziquantel
25mg/kg body weight single dose
Epidemiology
World wide
Common among children due to ingestion of
infected grain beetles, dried fruits, flour and
cereals
Prevalence of H. diminuta in Philippine rats is
about 8%

73. Dipylidium caninum
Double Pored Dog Tapeworm
Presence of bilateral genital pores in each
segment (di: 2; pylis: gate): 2 entrances
Common intestinal parasite of dogs

74. Dipylidium caninum
Adult
10-70 cm in
length
Pale reddish

75. Dipylidium caninum
Scolex
Small and
globular
4 deeply cupped
elliptical suckers
Protrusible/retrac
tile rostellum
Rostellum has 1-
7 rows of rose
thorn shaped
hooklets

76. Dipylidium caninum

77. Dipylidium caninum
Strobila
200
proglottids
narrow

78. Dipylidium caninum
Mature
proglottids
2 sets of male
and female
reproductive
organs
Bilatera genital
pores

79. Dipylidium caninum
Gravid
proglottids
Have size and
shape of
pumpkin seeds
Filled with
capsules or
packets of 8-15
eggs enclosed n
an embryonic
membrane

80. Dipylidium caninum
Proglottids

81. Dipylidium caninum

82. Dipylidium caninum
Ova
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

83. Dipylidium caninum
Intermediate hosts
Ctenocephalides canis : dog flea
Ctenocephalides felis : cat flea
Pulex irritans : human flea
Trichoedectes canis : dog flea

84. Dipylidium caninum
Pathogenesis
Dipylidiasis
Rarely multiple
Symptoms are minimal
Slight intestinal discomfort
Epigastric pain
Diarrhea
Anal pruritus
Allergic reactions

85. Dipylidium caninum
Treatment
Praziquantel
5-10 mg/kg body weight single dose
Epidemiology
USA
Rhodesia
Argentina
China
Philippines

86. Dipylidium caninum