Cestodes by Dr. Rakesh Prasad Sah

1. Helminths (Cestodes)
By Dr. Rakesh Prasad Sah
Assistant Professor

2. Introduction to Helminths
• Multicellular, bilaterally symmetrical metazoa.
• Have 3 germ layers (triploblastic metazoa)
• Helminths – 2 Phylum

3. Cestodes Vs Trematodes Vs Nematodes
Differences between Cestodes, Trematodes & Nematodes
CESTODES TREMATODES NEMATODES
Shape Tape like
segmented
Leaf like
unsegmented
Elongated, cylindrical,
unsegmented
Sexes Sexes not separate
Monoecious
Hermaphrodite
Sexes not separate
Monoecious except
Schistosoma
Sexes are separate
Diecious
Head end Suckers, often with
hooks
Suckers, no hooks No suckers, no hooks, well
developed
Alimentary
canal
Absent Present,
incomplete,
No anus
Present, complete,
anus present
Body cavity Absent Absent Absent

4. Cestodes

5. Had lunch????

6. Post-prandial somnolencia!!!

7. General characters of cestodes
• Long, segmented and tape-like
• Tapeworms
• Flattened dorsoventrally
• Habitat: Adult worms in intestinal canal of humans and animals
• Head is provided with suckers (Slit like or cup like) and sometimes with
hooks (attachment)

8. General characters of cestodes
• Sexes are not separate (Hermaphrodite)
• Body cavity is absent
• Alimentary canal is entirely absent
• Excretory and nervous system are present
• Reproductive system – highly developed and complete in all segment.

9. General characters of cestodes
• 3 regions in an adult worm
1. Head (Scolex)
2. Neck
3. Strobila (body or trunk) containing series of segments
(Proglottids)
• Based of maturity of reproductive organ
– Immature,
– Mature,
– Gravid

10. Slide Title
1.Immature:
Male and female organs not developed
2. Mature:
Male and female organs developed, male organs appear first
3. Gravid:
Uteri filled with eggs (other organs atrophied or disappeared)

11. Slide Title

12. ADULT WORM

13. Slide Title
• Scolex (Head)
– Organ of attachment
– Adult tapeworm attach to the intestinal wall
– Suckers are and in some species, hooks are present
on scolex.
– Rosetellum (apical protrusion on scolex)  usually
present but may be absent.
– Rosetllum  may or may not be armed with hooks

14. Slide Title
• Neck
– Portion lies behind the scolex is
termed as neck
– Proglottids  generated from the
neck  continuously during the
entire life of the adult worm.

15. Strobila
• Composed of a chain of segements
(proglottids)
• Types
– immature
– Mature
– gravid

16. Slide Title
• Mature proglottids
– Present behind the immature
– Are larger & contain fully developed reproductive organs.
– Testes & ovaries +nt in each mature segements
– Hermaphroditic

17. Slide Title
• Gravid
– Completely occupied  uterus  filled with eggs.
– Contains several testes, a bilobed ovary and uterus.
• Body cavity  absent
• Food  absorbed thru body surface.
• Excretory & nervous system  Rudementary (not well developed)

18. Systemic classification of cestodes
Order Family Genus Species
Pseudophyllidea Diphyllobothridae Diphyllobothrium D. latum
S. mansoni
S. theileri
S. erinace
Cyclophyllidea Taeniidae Taenia T. Solium
T. Saginata
T. Asiatica
T. Multiceps
Echinococcus E. Granulosus
E. Multiloculais
Hymenolepididae Hymenolepis H. Nana
H. Diminuta
Dilepididae Dipylidium D. caninum

19. Classification according to habitat of the adult worms and larval forms
Order Adult worms in man Larval forms in man
Pseudophyllidea Diphyllobothrium latum Spirometra mansoni
Spirometra theileri
Cyclophyllidea Taenia solium Echinococcus granulosus
T. Saginata E. Multilocularis
Hymenolepis nana Taenia solium
H. Diminuta T. Multiceps
Dipylidium caninum

20. • Is commonly known as fish tapeworm or the
broad tapeworm.
Morphology
Adult worm
• Longest tapeworm found in man (10metres and
3000 proglottids)
• Found in small intestine usually in the ileum.
• Scolex
– 2-3mtr in length.
– 1mm in breadth.
– No rostellum and hooklets.
Diphyllobothrium latum
•Neck
Just behind scolex
•Proglottids
3000 or more proglottids
10-20mm broad and 2-4 meter

21. • Egg
– Yellowish brown in
colour (bile stained)
– Oval in shape
– 65µm by 45µm
– does not float in
saturated salt solution

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Diphylobothrium latum
Definitive host Man
1st Intermediate host Cyclopes
2nd Intermediate host Fish
Infective form Pleurocercoid larva
Mode of transmission Ingestion
Site of localization Small intestine
(Fish Tape Worm)

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Adult worms (intestine)
Operculated eggs (stool)
Coracidium escapes
Cyclops eat coracidium
Procercoid larva in cyclopsFish eats infected cyclops
Plerocercoid larva in fish
Man eat infected fish
Larva release in intestine
Life Cycle – D latum

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Dr. Sudheer Kher2
Diphyllobotrium latum - the fish tape worm
• Common in fish eating
carnivores with little
host specificity. Salmon,
trout, perch, white fish,
eel, pike, etc.
• Adults get quite long
(10 m) and shed up to a
million eggs per day
• Eggs must reach water
for embryonation
• After several days a
coracidium hatches
through the operculum
and is eaten by a
copepod
http://www.dpd.cdc.gov/DPDx/HTML/Diphyllobothriasi
s.htm

25. • Infection of humans cause no or little
symptoms (abdominal discomfort,
nausea, diarrhea are rare)
• The parasite takes up large amounts of
Vitamin B12
• In patients with genetic deficiencies in
Vit B12 uptake the parasite competes
effectively for the entire vitamin leading
to severe pernicious anemia

26. • Egg
– Yellowish brown in
colour (bile stained)
– Oval in shape
– 65µm by 45µm
– does not float in
saturated salt solution

27. • Taenia saginata Beef tapeworm or
unarmed tapeworm.
• Taenia solium  Pork tapeworm or
armed tape worm
Taenia saginata & Taenia solium

28. Differentiating Features of Taenia solium and Taenia saginata
Features T. Solium T. Saginata
Length 2-3 meter 5-10 metres
Head Small, globular; rostellum and a double
row of hooks. Four suckers present, which
are not pigmented
Large, quadrate; without rostellum and
hooks. Four suckers present, which may
be pigmented
Neck Short Long
Segments (Proglottids)
Number <1000 1000-2000
Expulsion In chains of 5 or 6 Expelled singly
Uterus Lateral branches 5-10 on each side Lateral branches 15-30 on each side
Vaginal Sphincter Absent Present
Ovaries Two in number with an accessory lobe Two in number without any accessory
lobe
Testes 150-200 follicles 300-400 follicles
Larva Cysticercus cellulosae, present in pig (I.H.)
and may also develop in man (D.H.)
Cysticercus bovis, present in cow (I.H.)
but not in man (D.H.)

29. • Eggs
– Liberated by the rupture of proglottids
– Spherical & bile stained
– 31-43µm in diameter
– Inner embryophore is thick-walled,
radially striated and brown in colour
– Does not float in a staturated solution of
common salt
– Infective only to cattle
Taenia saginata

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Taenia saginata
Definitive host Man
Intermediate host Cattle
Infective form Cysticercus bovis (larva)
Mode of transmission Ingestion
Site of localization Small intestine
(Beef Tape Worm) or unarmed tapeworm
Lenghth 5 meters
Max reported 25 meters

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Life Cycle – T saginata
Adult worms (intestine)
Eggs (stool)
Cattle ingest
Onchosphere release
Intestine penetration
Blood to muscles
Cysticercus (bladder larva)
Man eat undercooked beef
Scolex release in intestine

33. • Eggs
– Liberated by the rupture of proglottids
– Spherical & bile stained
– 31-43µm in diameter
– Inner embryophore is thick-walled,
radially striated and brown in colour
– Does not float in a staturated solution of
common salt
– Infective to both pig and man.
Taenia solium

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Taenia solium
Definitive host Man
Intermediate host Pig
Infective form Cysticercus cellulosae (larva)
Mode of transmission Ingestion
Site of localization Small intestine
Eggs
(Pork Tape Worm)

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Life Cycle - T solium
Adult worms (intestine)
Eggs (stool)
Pigs ingest
Onchosphere
release
Intestine penetration
Blood to muscles
Cysticercus (bladder
larva)
Man eat undercooked pork
Scolex release in
intestine

36. Life cycle

37. • Larval stage or cysticercus cellulosae (bladder worm) of Taenia
solium develops in the muscles of its intermediate host i.e. pig
• Muscles of tongue, neck, shoulder and ham are the most
commonly involved. Cardiac muscles may also be affected.
• A mature cyst an opalescent ellipsoidal body and the long
axis of cyst  parallel to the muscle fibre.
• Cyst develops further when ingested by man, its definitive
host.
Cysticercus cellulosae

38. • Man  gets infection  same way as pig  either by drinking contaminated water or
by eating raw vegetables infected with eggs.
• Autoinfection man harbouring adult worm unhygenic personal or by a reversal of
peristaltic movements of the intestine by which gravid segments are thrown back to
the stomach  equivalent to ingestion of thousands of eggs.
• May develop in any organs but are usually present in the subcutaneous tissues and
muscles.
• May aslo be found in the brain leading to epileptic attacks.
• Cysts calcified over a period of 5-6 yrs. (Cysticercosis)
• Neurocysticercosis (NCC)  most serious form of cysticercosis
Cysticercosis

40. • Larval stage or cysticercus bovis (bladder worm) of
Taenia saginata  muscles of I.H. i.e. a cow or a
buffalo.
• Contains scolex without hooks and rostellum
invaginated at one side.
• Develop into adult worm when ingested by man, its
D.H.
• Does not occur in man.
Cysticercus bovis

41. Pathogenesis
• Asymptomatic
• Passage of proglottids in feces
• Discomfort in perianal region
• Symptomatic
– Abdominal discomfort
– Nausea
– Change in appetite
– Weakness and weight loss
• Rare
– Cholangitis

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Diagnosis & Treatment
Disease Digestive disturbances
Neurocysticercosis – 60%
Diagnosis Eggs / segments in stool
Treatment Niclosamide / Praziquantel
US / CT / MRI
ELISA
Albendazole (NC)

43. • Avoidance of eating raw or undercooked meat.
• Avoid eating raw vegetables grown on soil irrigated
by sewage water.
• Effective treatment of infected individual to prevent
infection of the I.H.
• Personal hygiene to prevent the risk of acquiring
cysticercosis by autoinfection.
Prevention

44. Echinococcus granulosus
• Hydatid worm or Hyper Tape-worm
• Man sheep and dog have close contact
Organism characteristics
•Adult worm: 3 to 6 mm
•Dogs intestine
•Life span 5-20 months
•scolex :4 suckers with rostellem two pairs of hook
•neck :
•strobila :only three segments
– immature
– mature
– gravid

45. Adult Echinococcus
granulosus

46. • Egg :
– 32-36µm in length and 25-
32µm in breadth
– ovoid
– Hexacanth embryo
– 3 pairs of hook lets
– Indistinguishable from taenia
• Larval form (hydatid cyst)

47. • Definitive host : dog ,wolf ,fox and jackal
• Intermediate host : sheep , pig ,cattle ,goat , and man
Mode of infection
•Direct contact with infected dogs.
•Feeding dogs from same dish.
•Uncooked vegetables contaminated with infected animal faeces .

49. Hydatid cyst
• Larval form (hydatid cyst)
• Develops in tissues (Liver)
• 1-5cm /year
• Cyst filled with fluid (hydatid fluid) and have
double layer
Ectocyst
•Outer layer, tough, acellular, hyaline membrane
•White of boiled egg
Endocyst
•inner/germinal lies on inner surface of ectocyst
•give rise to ectocyst , brood capsules, scolices &
daughter cyst
•Several proscolices develop in brood capsule
•each protoscolex gives rise to an adult worm

50. Internal structure of Hydatid Cyst

51. Hyadatid sand :
when the embryo break, free from the membrane and float in the fluid within
cyst, called as hydatid sand. It secretes hydaid fluid.
Hyadatid fluid :
–clear ,colourless
–low specific gravity 1.005 to 1.010
–acidic pH 6.7
–contain NaCl , Na2So4 ,Sodium phosphate,
–sodium & calcium salts of succinic acid
–antigenic {casoni’s test }
•Highly toxic  Anaphylaxis

53. Hydatid cyst

54. Clinical feature
• Remains symptomsless many years but may pressure effect & visible swelling.
• Chronic abdominal discomfort may be present in case of liver cysts.
• If cyst ruptures  either spontaneously, from trauma or during surgery  anaphylatic
shock or death
• Cysts in lungs  asymptomatic but may cause cough, breathlessness or chest pain.
• Rupture produce fever, pruritis,urticaria ,eosinophilia and fatal anaphylaxis
•Liver (commonest site and right lobe is
frequently involved)
•Lung
•Brain
•Heart
•Kidney
•Spleen
•Muscles

55. Lab diagnosis
Casoni’ test
Blood Exam : Eosinophilia
Serology :
• ELISA ,
• COMPLEMENT FIXATION TEST(CFT)
• INDIRECT HEAMAGGLUTINATION ASSAY(IHA)
• LATEX AGGLUTINATION ASSAY
• X ray
• CT
HISTOPATHOLOGICAL EXAMINATION

56. Casoni’ test
• 0.2 ml fluid id
• A positive measures 5 cm
wheal

57. Treatment
• Praziquintel and albendazole
• Surgical intervention

58. Prophylaxis
• Not allowing dogs to eat carcasses of slaughtered
animals endemic areas
• Improving personal hygiene

59. Hymenolepis nana
• Dwarf tapeworm
• found throughout the world
• Smallest tapeworm infecting humans
• Hymenolepis :
– Hymen: meaning membrane,
– Lepsis: covering (Thin membrane covering the egg.
– Nanus: dwarf or small

60. Morphology
• 40 mm long and 1 mm wide.
• The scolex bears a retractable rostellum
armed with a single circle of 20 to 30
hooks.
• The scolex also has four suckers
• 200 -300 proglottids

63. • Eggs
– 30-45µm in diameter
– Non bile stained
– Outer covering thin
colourless
– Inner covering is
embryophore
– Polar filaments and yolk
granules
– Hexacanth embryo

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Hymenolepis nana
Definitive host Man
Intermediate host No
Infective form
Mode of transmission Ingestion
Site of localization Small intestine
Eggs
(Dwarf Tape Worm)
Internal autoinfection

65. • Infection acquired most commonly from eggs in the
faeces , which are transferred in food, by contaminated
fingers, or in sewage-contaminated drinking water.
• Immediately infective
• Infection through fecoral route
• the only cestode that does not require an intermediate
host to develop into its infective stage.

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Life Cycle – H nana
Adult worms (intestine)
eggs (stool)
ingestion
Onchosphere
release
Cysticercoid larva
Scolex release in
intestine

67. Clinical Manifestations
• enteritis,
• abdominal pain,
• diarrhoea,
• loss of appetite, restlessness, irritability,
• restless sleep, anal and nasal pruritus, vomiting, nausea,
bloody diarrhoea, hives, extremity pain, headache, dizziness
and behavioural disturbances.
• Occasionally epileptic seizures occur in infected children.

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Diagnosis & Treatment
Disease Digestive disturbances
Diagnosis Eggs / segments in stool
Treatment Niclosamide / Praziquantel

69. Treatment
• praziquantel
• niclosamide.

70. Prophylaxis
• Personal hygiene
• Sanitary improvement
• Avoid contaminated food and water