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1. Intoroduction to Class Cestoidea
The Tapeworms

2. Otline
• General feature of cestodes
• General morphology of cestodes
– Adult , Larva and Ova
• Clarification of cestode
• Major differences between order Cyclophyllidea
and Pseudophyllidea
• Geographical distribution Morphology, differential
characteristics, life Cycles of each species
• Laboratory diagnosis, control and prevention
methods for each species

3. Learning objectives
• At the end of ths unit the student will be
able to:
• Explain the general feature of cestode
• Explain the general morphology of Adult
larvae and ova
• Describe the classification of cestode

4. Objective…
• List the major differences between order
Cyclophyllidea and Pseudophyllidea
• Explain the geographical distribution
Morphology, differential characteristics,
life Cycles of each species
• Apply the necessary laboratory procedure
for detection and identification of cestode
parasite

5. General characteristics:
Adult
• Segmented long tape-like
worms
• Vary from few mm to several
meters
• No mouth/digestive system.
• Obtains its nutrient by
absorption through body
surface.

6. Body is divided into three main regions
a. Scolex (head)
b. Neck
c. Strobila made
up of proglottids
Morphology

7. Scolex
– “head” of the organism
– Has holdfast organs to keep the tapeworm in
place
– Three main types of Scolex

8. • Three main types of Scolex
Cyclophyllidae
A-Globular head with 4
Muscular Sucker
B- 4 Sucker +Rostellum
armed with hooks
Pseudohyllidea
Bothria-Shallow grooves
or pits

9. • Area where new
segments are
created
• Give rise to
proglottids in
strobila.
Neck

10. Proglottids/segment
• Proglottid
– Set of reproductive organs
– Includes male and female organs and
genital pore
• Segment
– Segments may have one or more
proglottids
– Body divisisions
– More mature as gets farther from neck
• Size and shape of segment along with
number of proglottids and location of
genital pore key to identification many of the
tapeworms.

11. RED = Male BLUE = Female

12. Reproduction
• Sex:- Hermaphrodites
• Have well developed reproductive
system.
• Reproduction
–Sexual-Oviporous
–Asexual-Sometimes multiplication
with in larval forms

13. Strobila • Is the entire chain of
proglottids

14. Strobila is divided into three regions:
• a/ Immature segment:
– near neck, sex organs are
immature.
• b/ mature segment:
– large segment, sex organs are
fully mature.
• c/ gravid segment:
– found at the tail end, uterus is
filled with eggs

15. Egg: -
• Two type
– Operculated, immature when voided to the
external environment.
– Non-operculated ,fully embryonated when
voided to the external environment.

16. Operculated
Operculum

17. Non-operculated

18. Larvae:
• Generally two types
1. Solid :
– eg. Procercoid, Plerocercoid,
cysticercoid
2. Cystic ( true bladder) can be with:
– Single scolex
eg. Cysticercus;
– Many scolexes and/or with daughter cyst
eg. hydatid cyst, coenurus cyst, etc

19. Cysticercus Coenurus
Cysticercoid
Strobilocercus

20. Classification
1. Order Cyclophyllidea
1. T. saginata,
2. T. solium,
3. Hymenelopis sps
4. Echinococcus
granulosus
2. Order Pseudophyllidea
1. Diphyllobothrium latum
• Less medically important:
– Order Cyclophyllidea
• T. multiceps
• Dipylidium caninum
• Echinococcus
multicuralis.
– Order Pseudophyllidea
• Spirometra species

21. Life cycle
• Complete in two host (exception H.nana)
• Haibtat:- Adult live in small intestine
• Man is:-
• The only/main DH for T. saginata, T. solium, H. nana
and D. latum
• IH for E. granulosus and E. multilcolaris
• DH & IH for H. nana and T. solium

22. Egg
Coracidium Oncosphere
Cysticercus Cysticercoide, coenuruses, Hydatid Cysts
Intermediate
Host
Adult
Definitive
Host
Cystic larval form
Solid larval
form
procercoid larva
Plerocercoid larva
Operculated, Non-operculated
1-Pseudohyllidea
2-Cyclophyllidea

23. Order- Pseudophillidea Order –Cyclophillidea
1. Scolex Spoonshaped, grooves - globular with 4 suckers
2. Genital pore - venteral - marginal
3. Utrine pore -Present(ventral) - absent
4. Uterus - coiled - sacular tubular or branched
5. Ova - operculated - non-operculated
6. Onchosphere - ciliated - non-ciliated
7. Rostellum - absent - present
8. Progilottids - broader than long - longer than broader
9. Larval forms - solid - cystic

24. • Geographical Distribution:-
– T. saginata
• World wide distribution where cattle are raised and beef is eaten
raw or under cooked.
• Very common in Ethiopia
– T. solium
• Not widely distributed as T saginata.
• Common in all areas where raw or partially cooked pork is eaten.
• Common throughout Mexico, South America and southern Africa &
southern Europe.
• Not reported from Ethiopia
Taenia species

25. Morphology:
• Adult:
– Size: 4-10 m long (can
reach up to 20 m)
– Colour: ivory white
– Strobila : 1000-2000
proglottides
– Mature segment: 1-2cm
long
T. saginata
• Adult
– Size: 2-3m
– Colour: pale blue
– Strobila: 800-1000
Proglottides
– Mature segment :0.5-1.5
cm
T. solium

26. Taenia saginata
Scolex (head):
• Quadrate, with four suckers, no
hooks, no rostellum on scolex
• Size-2mm across

27. Taenia solium
Scolex has
• Four sucker
• two rows of hooks on a prominent
rostellum
• Size-1mm

28. Taenia sp.
• Larval stage is cysticercus
– Invaginated scolex in fluid filled body
– Cysticercus bovis-T saginata
– Cysticercus celluless-T solium
• Eggs are very round with very thick walls.

29. Transmission and life cycle
• Transmission
– Humans become infected by ingesting raw or
undercooked meat infected with cystcerus
larvae:
• Beef- T saginata
• pork meat –T.solium
– T. solium can also be transmitted by :
• Ingesting ova in food or water
• Internal autoinfections

31. Taenia solium
• Distinct difference with T. saginata is that humans
can be infected with egg stage and onocosphere
migrates to some site in body and develops into
cycticercus
• This can be serious, called Cysticercosis

33. Clinical manifestation
• T saginata
–Taeniasis.
• Usually asymptomatic but may
cause dizziness, abdominal pain,
diarrhea, headache and nausea.
–Proglottids obvious in feces.
– Proglottides have a strong tendency
to crawl from the anus during the day
when its host is active

34. • T. solium
–Taeniasis
• Major symptoms of taeniasis are as a
result of the adult worm.
• These include abdominal pain, loss
of appetite, and
–Cysticercosis
• T. solium ( when infected by eggs)
cause cysticercosis (larval cysts in
lung, liver, eye and brain) resulting in
blindness and neurological disorders.

35. Laboratory Diagnosis
• Detecting eggs in faeces .
• Identifying macroscopically
– gravid segments in faeces
– scolex recovered from clothing or
passed in faeces.
• In addition
• T.saginata-
– ova on perianal skin (cellotape slide)
• T.solium ( cysticercosis)
– Finding calcified larvae in
histological or X-rays examination .

36. Egg : T.solium &T.saginata
• Size: - 33-40 m
• Shape: -Round
• Colour: - Shell-dark
yellowish-brown,
• Content: light yellowish
gray.
• Shell:-Thick, Smooth,
brown, radially straited
(embryophore)
• Content: - A round granular
mass enclosed by a fine
membrane with six hooklets

37. • T. saginata ova stains red
(acid fast) in Ziehl-
Neelsen stain
• this character helps to
differentiate it from
T.solium which do not
have red color in such
staining ( not acid fast)
Morphologically eggs of T.saginata and T. solium are
indistinguishable unless stained by AFB

38. Taenia saginata
• Gravid proglottide
• Detach when fully develop
and pass through the
anus independently.
• Color- white and opaque
• Size- 20mmX6mm
• Uterus- > 13 main (15-
30) lateral uterine
branches.

39. Taenia solium
• Gravid proglottides-
• Grey-blue and transluscent
• Size-13mmX8m
• 7 to 12, on average 10 lateral
compound uterine branches.
• Small chains of 3-4 rectangular
segments found in the faeces

40. • Hymenolepis nana-
Dwarf Tape Worm

41. Hymenolepis nana
• Dwarf Tapeworm
– Vampirolepis nana
• Definitive Host: Humans, rodents
– Most common tapeworm of humans in the
world
– 1% rate of infection in the southern U.S.
– 97.3% rate of infection in Moscow, Russia
• Intermediate Host: Larval and adult
beetles (but optional)
– Larval stage, cysticercoid, can develop in
D.H. if it eats the eggs
• Probably a recent evolutionary event

42. • Small tapeworm
• Scolex has rostellum
with row of hooks
• Proglottids are wider
than long with lateral
genital pore

43. • Geographical Distribution:-
– H.nana is widely distributed in countries
with warm climates than in cold climates
and fairly common in Ethiopia.
– Children are more commonly infected than
adults.

44. • Mode of Transmisssion: -
– Ingestion of egg with contaminated food,
drink or finger.
– Autoinfection.
• Life Cycle: H. nana has a direct life
cycle with a human host serving as both
definitive and intermediate host.

46. Hymenolepis
dimunata
• Slight larger than H.
nana but still very
small.
• Scolex has very
small rostellum with
no hooks
• Proglottid same as
H. nana but larger.

48. • Egg: H nana
– Size: 35-50m
– Shape: oval, almost round
– Shell: double; thin external
membrane and internal membrane
often thicker at the poles. Thread like
polar filaments coming from both
poles
– Colour: colour less or very pale gray
– Content: Rounded mass (embryo)
with six refractile hooklets arranged
in fan shaped.

49. Egg: H dimunata
• Color:-Yellow-brown or
bile pigmented.
• Size:-70 by 60μm
• Shell with double shell
and with out thread like
polar filaments.
• Content: A rounded
embryo containing six
hooklets arranged in fan
shape.

50. Echinococcus granulosus
• Sheep Tapeworm
• Definitive Host: Carnivores including dogs,
wolves, and coyotes
• Intermediate Host: Herbivores including
sheep and mice.
• Occasionally infect humans.
• The hyatid cysts growin humans very slowly
and can overcrowd organs
• Geographic Distribution: Most common in
sheep raising countries
– New Zealand and Australia highest incidence

51. MORPHOLOGY
• Smallest of all tapeworms
– Scolex, neck, 3 segments
– Segments look like Taenia
sp.
• Largest larval stage of all
tapeworms
– Hydatid cyst

53. Clinical feature and Pathology:
• The symptoms, depend upon the location of the cyst.
• Large abdominal cysts produce increasing
discomfort.
• Liver cysts cause obstructive jaundice.
• Peribronchial cysts may produce pulmonary
abscesses.
• Brain cysts produce intracranial pressure and
Jacksonian epilepsy.
• Kidney cysts cause renal dysfunction.
• The contents of a cyst may produce anaphylactic
responses

54. E.
granulosus
hydatid
cyst

55. Laboratory Diagnosis
• Histological examination to find larvae
• X-ray examination to find larvae
• Examination of cystic fluid for brood
capsules and protoscoleces
• Casoni's skin test

56. Dipylidium caninum
Dog Tapeworm
• World wide
Distribution
• Dogs or cats
(humans rarely) as
the definitive host
• Fleas or lice are
the intermediate
host.
• Habitat:
• Adult: mucus membrane of
small intestine of carnivores
such as dog, cat, Man
• Cysticercoid larvae: In the
body cavity of insects
• Egg: in the faeces of dog,
cat, man

58. Dipylidium caninum
• Flea or louse
ingests the eggs in
the perianal region
of the dog or cat.
• The dog or cat (or
human) is infected
when they ingest a
flea or louse
infected with the
metacestode state
(cysticercoid) Dog flea

59. Dipylidium caninum
Proglottids of Dipylidium
caninum compared to a
match stick.
These are often passed
intact in the feces of an
infected dog.
When the proglottids
dry, their appearance is
similar to grains of rice.

60. Dipylidium
caninum
• Egg: 5-15 eggs in
capsule
• 40m in size and
yellowish brown in
color

61. Eggs
Taenia sp.
Diphyllobothrium
latum
H. nana
Dipylidium
caninum
H. dimunata

62. Diphyllobothrium latum
Common name: Fish tapeworm
• Geographical Distribution:-
– Widely distributed in the lake areas of
Europe, Asia, Far East, North America,
South America and Central Africa .

63. Diphyllobothrium latum
Fish tapeworm
• Important parasite of
man.
• Definitive hosts can be
humans, dogs, foxes,
cats, mink, bears, and
seals.
• Site of attachment :
small intestine.

64. Diphyllobothrium latum
Fish tapeworm
• humans are infected
with the plerocercoid .
• In humans the
tapeworm can reach
a length of 10
meters (>30 feet)
and produce over a
million eggs a day! .

65. Diphyllobothrium
latum
• Scolex has bothria
– Shallow groove
• Segments have one
proglottid
– Wider than long
egg-
58-76µm by 40-51µm
Broadly ovoid
Light golden yellow,
Operculated
Thick shell
Contains immature

66. Morphology
Adult: the largest tapeworm
Size: 10m or more
Grayish-yellow in colour
Scolex is elongated, spoon shaped,
longitudinal suctorial
mangroove/bothria/slits with no
rostellum and hooklets.
Long and slender neck

68. • Clinical feature and Pathology :
– Clinical symptoms may be mild, depending on the
number of worms.
– They include abdominal discomfort, loss of weight,
loss of appetite and some malnutrition.
– Anemia and neurological problems associated
with vitamin B12 deficiency are seen in heavily
infected individuals.
• Laboratory Diagnosis
– Eggs in the faeces
– Scolex in the faeces
– Adult worms in the faeces

69. Egg:
• 58-76m by 40-51m
• Broadly ovoid
• Light golden yellow,
Operculated
• Thick shell
• Contains immature
embryo