CESTOD

1. CHAPTER THREE
Introduction to Class Cestoidea
• The Tapeworms
PLATYHELMINTHE

2. Learning objectives
 At the end of this unit the student will be able to:
 Explain the general feature of Cestodes
 Describe the classification of Cestodes
 Explain the geographical distribution Morphology,differential
characteristics, life Cycles of each species
 Apply the necessary laboratory procedure for detection and
identification of cestode parasite

3. General Classification
 Plathelimenthes:
1. Cestodes-tapeworm
Tania species- T. saginata & T. solium; others
2. Trematodes
2.1. Blood flukes: Schistosomes species (e.g. S. mansoni-intestinal,
S hematobium-urinary Schistosoma
2.2. Other flukes (Liver, lung, intestinal)

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

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

6. Classification
1. Order Cyclophyllidea
1. T. saginata
2. T. solium
3. Hymenelopis spps
4. Echinococcus granulosus
2. Order Pseudophyllidea
1. Diphyllobothrium Latum

7. Life cycle
• Complete in two host (exception H.nana)
• Habitat:- Adult live in small intestine
• Man is:-
• The only/main DH for T. saginata, T. solium, H. nana and D. Latum
Characteristic features of Tape worms (Cestodes)
Body is tape- like and is made up of a head (scolex) and many
proglottides (segments).
The head attaches the tapeworm to its host via suckers and hooks.
With few exceptions, adults live in the infesting tract with some
species growing to great length.
Proglottides are formed form behind the head.

8. Taenia species
Infection with Taenia tape worm is called Taeniasis.
Humans are definitive hosts.
Taenia saginata -beef tape worm
Taenia solium – pork tape worm
Taenia saginata
 Epidemiology:-
Is distributed world-wide.
Is found in countries where cattle are raised and beef is
eaten raw.

11. Clinical features and pathology
The majority of infections are asymptomatic.
Symptoms:-abdominal pain with intestinal disturbance, weight loss,
and loss of appetite.
 Occasionally; Intestinal obstruction, Appendicitis and/or cholangitis
(due to migrating segments)
Laboratory diagnosis
 Identifying gravid segments recovered from clothing or passed in
faeces.
 Microscopic detection of eggs in faeces

12. Prevention and control
 Avoiding eating raw or insufficiently cooked meat
 Inspecting meat and condemning any found to contain
cysticerci.
 Proper use of latrines and not using untreated human faeces to
fertilize pastureland.
 Treating infected persons
 Health education

13. Treatment
• Drug of choice: Praziquantel. Other drugs like
Niclosamide can be used
• Alternative: paromomycin, and Atabrine (quinacrine
hydrochloride)

14. Taenia solium
Epidemiology
• T. solium is not as widely distributed as T.saginata
• It occurs in places where human faeces reach pigs and pork is eaten
raw or insufficiently cooked.
Transmission and Life cycle
• Transmitted by eating raw or insufficiently cooked pork which
contains infective larva (cysticercus cellulosae)

15. Life cycle is similar to T.saginata except
• Occasionally, in a human host, the gravid segments are regurgitated
and eggs reach the stomach.
• Then, embryos carried in the blood circulation to muscles,
subcutaneous tissues, the brain, spinal cored, eyes and develop in to
cysticerci.
• This can occur by ingesting viable egg
•  Causes cysticercosis.

16. Clinical features and pathology
Infection with the tapeworm of T. solium is usually
asymptomatic.
There may be abdominal pain, and loss of appetite
 In cysticercosis:-
 Cystic nodules occur in subcutaneous tissues and muscles.
If it occurs in the brain, it causes epilepsy and other CNS
disorders.

17. Laboratory diagnosis
• Same as that of T.saginata
• Cysticercosis: diagnosed serologically by detecting
specific antibodies.
Prevention and control
• Same as that of T.saginata
• In addition, avoiding access of pigs to human faeces can
be used.

18. Treatment
• Treatment for adult tapeworm is the same as that of
T.saginata.
• Treatment of Cysticercosis, surgical removal of the larvae
from the infected tissue.

19. Hymenolepis nana
• Dwarf Tapeworm - the smallest (3–4 cm) tapeworm
 The only tape worm capable of completing its life cycle in one
host
 widely distributed in countries with warm climates
• Definitive Host: Humans, rodents
 Most common tapeworm of humans in the world
 Children are more commonly infected than adults

20. H. nana…
• Egg:
– Shell: double; thin external
membrane and internal
membrane
– contain a six-hooked
oncosphere
– Thread like polar filaments
coming from both poles

21. o Mode of transmission:
i. Ingestion of egg: with contaminated food, drink or finger
• Eggs can’t survive more than 10 days in the external env’t
ii. Autoinfection
iii. Ingestion of infected arthropods
o Life Cycle: has a direct life cycle
– human: serving as both DH and IH
– The oncospheres (hexacanth larvae) penetrate the intestinal
villus and develop into cysticercoid larvae
H. nana…

22. Life cycle …>>>

23. Clinical manifestation
• More common in children
• Majority of infections are asymptomatic
• Symptoms: abdominal pain, nausea, vomiting, weight loss,
diarrhea
• Toxins released from the worms can cause allergic reactions.
• Severe and sometimes disseminated infections can occur in
malnourished and immunosuppressed persons.

24. Laboratory Diagnosis
• Finding the eggs in feces
• Caution: Eggs are infective when excreted in the feces.

25. Echinococcus granulosus
Common name: Hydatid worm or minute tape worm of dog
Geographical Distribution
 worldwide, and more frequently in rural, grazing areas where dogs
ingest organs from infected animals
 In Ethiopia
common among the pastoral people in the South and
South-East of Ethiopia
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26. Habitat
Adult: 3-6mm ,mucus membrane of small intestine
of carnivores such as dog, fox
Scolex : with 4 suckers, rostellum with 2 rows of
hooklets
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Cont…

27. Cont..
Hydatid cyst/larvae: in the different body parts (liver,
lung, brain, etc) of man & herbivorous animals
Egg: in the faece s of dog, fox, and jackals ,morphologically similar
to Taenia species
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28.  Gravid proglottids release eggs that are passed in the feces by dogs
or other carnivorous
 Human acquire infection by accidentally ingesting eggs, usually
hand –to-mouth contact with infected dog faeces
 the egg hatches in the small bowel and penetrates the intestinal wall
 migrates through the circulatory system into various organs,
especially the liver , lungs ……
 In these organs, develops into a cyst that enlarges gradually
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Life Cycle

29. Life cycle of E.granulosus
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30.  The symptoms depend upon the size & location of the cyst
Large abdominal cysts produce increasing discomfort
Liver cysts cause obstructive jaundice
 in the lung : cough ,dyspnea and chest pain
Brain cysts produce intracranial pressure & epilepsy
Kidney cysts cause renal dysfunction
 Cyst rapture : fever ,anaphylactic shock and death
 may also lead to dissemination of infection
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Clinical feature and Pathology

31. 1. Radiologic examination
Pulmonary cysts and calcified cysts can be visualized
2.Serology
 Antibodies against hydatid fluid antigens detected by ELISA or
indirect hemagglutination test
3.Examination of cystic fluid following surgical removal of a cyst or
fine needle aspiration
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Laboratory Diagnosis

32. Diphyllobothrium latum
• Known as the fish tapeworm
• Humans are the important definitive hosts and fish is IH.
• widely distributed in the lake areas of Europe, North America and
the Far East.
• It is also found in parts of Asia and South America, particularly
Chile.
• D. latum is transmitted by ingesting plerocercoids (infective
larvae) in raw or undercooked fish.

33. Transmission
1. Plerocercoid larvae
ingested in raw or
undercooked fish
Human host
2. Larvae attach to wall of small
intestine.
3. Become mature tapeworms
4. Eggs produced and passed in
feces
Fresh water
5. Eggs reach water.
Hatch coracidia.
Crustacean host
6. Coracidia ingested by
crustacean. Coracidia →
procercoids
Fish host
7. Fish ingests infected
crustacean.
8. Procercoids migrate to
muscles. Become
plerocercoids.
Life cycle

34. Life cycle…

35. Clinical feature and Pathology :
– Abdominal discomfort, loss of weight, loss of appetite
– Megaloblastic anemia and neurological problems associated with
vitamin B12 deficiency
Laboratory Diagnosis
– eggs in the faeces
– scolex in the faeces
– adult worms in the faeces
Prevention: good personal hygiene and avoidance of fecal
contamination of food and water.
D. Latum …

36. Laboratory Diagnosis
Egg of D. latum
yellow-brown and oval ( 70x45µm)
Has an operculum (lid) which is
usually difficult to see.
Contains a mass of granulated yolk
cells surrounding an undeveloped
ovum.