Platyhelminthes

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2. Trematodes (Flukes)
Trematodes (Flukes)
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3.  According to the site they inhabit , there are four
groups of trematodes (flukes):
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1. Blood flukes Schistosoma species:
Main species: S. Mansoni
S. haematobium, S. japonicum
2. Liver flukes
(in the liver and biliary duct)
Large liver flukes:
(Fasciola hepatica and F. gigantica)
Small liver flukes:
Clonorchis sinensis, Opisthorchis viverrini
3. Intestinal flukes
Large intestinal fluke:
(Fasciolopsis buski)
Small intestinal flukes:
(Metagonimus and Heterophyes)
Paragonimus westermani 4. Lung fluke
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4. Blood Flukes (Schistosomes)
The adult live in the veins that drain the intestine or the
urinary bladder (species dependent)
 Adults are Cylindrical shaped
 Sexes are separate
Schistosomiasis is caused by blood trematodes(flukes)
Freshwater snails serve as intermediate host
Humans the most significant definitive host
Cercaria is the infective stage
Transmission--- transcutaneous
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5. Cont…
The three main species infecting humans are:
- Schistosoma mansoni
- Schistosoma haematobium
- Schistosoma japonicum
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6. Cont….
Habitat:
 Adults (male and female )
– S. mansoni – veins of Large Intestine
– S. haematobium – veins of bladder ,prostate,
seminal vesicle
– S. japonicum – veins of small intestine
Egg:
 In the faeces (intestinal schistosomiasis )
 In the urine (urinary schistosomiasis )
Cercariae:- In fresh water (infective to human)
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7. Schistosoma mansoni
Common name: Manson’s blood fluke
- Causes Intestinal schistosomiasis (Intestinal bilharziasis)
Distribution: many African countries, S. America, Middle East
In Ethiopia: reported from all administrative regions
Morphology:
 Adults:
 Egg: has triangular lateral spine at one pole
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8. Schistosoma Haematobium
Common name: Vesical blood fluke
- Causes urinary schistosomiasis
Distribution: Africa, middle East, S. Europe
In Ethiopia – Awash, Wabeshebele, Asossa
Egg: has terminal spine at one pole
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9. cercaria cercaria and adult
Eggs,
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10. Life cycle of Schistosoma species
• Eggs are eliminated with feces or urine
• The eggs hatch and release miracidia , which swim
and penetrate specific snail intermediate hosts
• Inside the snail develop to sporocysts (two
generations), then to cercariae
• Cercariae release from the snail ,
• Infective cercariae swim in water (river, pond
lake..) penetrate the skin of the human host ,
• Shed their forked tail, becoming schistosomulae
(miracidium /miracidia , cercaria / cercariae , schistosomulum/ schistosomulae)
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11. Cont…
 Schistosomulae migrate to heart, lung,
then to liver to develop into adult
 Adults migrate to mesenteric veins or
veins around urinary bladder, depending
on species to produce eggs by female
worms
 The eggs are moved progressively
toward the lumen of the:
 intestine(S. mansoni )
= then passed in faeces
 bladder and ureters (S. haematobium)
=passed in urine
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12. Life cycle of Schistosoma species
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13. Developmental stages of blood Fluke
(Schistosoma species)
Egg miracidium sporocyst
cercaria
Schistosomulae
Adults
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14. Immunopathology
Host immune response against adult worm is
minimal
Eggs induce intense inflammatory reaction,
leading to granuloma formation
Granuloma consists of egg at center surrounded
by eosinophils , macrophages and lymphocytes
Larvae inside the egg produce enzymes that aid
in tissue destruction and allow the eggs to pass
through the mucosa and in to lumen of bowel (S.
mansoni) and bladder (S. haematobium).
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15. Schistosoma granuloma in the Liver
A section of an egg is visible in the center of the granuloma
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16. Clinical Features
Syndromes include:
1. Cercarial dermatitis :- Penetration of skin by
cercariae causes transient dermatitis (swimmers' itch)
2. Acute schistosomiasis (Katayama's fever) may
occur weeks after the initial infection, especially by
S. mansoni and S. japonicum.
Associated with heavy primary infection and the
initiation of egg production
Manifestations include fever, abdominal pain,
diarrhea, hepatosplenomegaly, lymphadenopathy
and eosinophilia.
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17. 3. Chronic schistosomiasis
 May have mild, chronic bloody stools due to passage of
egg through intestinal wall
 Host reaction to eggs lodged in the intestinal/bladder
mucosa leads to the formation of
- Granuloma
- Ulceration and
- Thickening of the wall
..
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18. Chronic…
Continuing infection may cause granulomatous
reactions and fibrosis in the affected organs, which
may result in manifestations that include:
Colonic polyposis with bloody diarrhea
(Schistosoma mansoni mostly);
Portal hypertension with hematemesis and
splenomegaly (S. mansoni, S. japonicum);
Cystitis and ureteritis with hematuria, which can
progress to bladder cancer(S. haematobium)
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19. Chronic…
• In less than 10% of
cases, granulomas
can cause blockage
of blood flow in liver
causing
enlargement of the
spleen and fluid
retention in
abdomen.
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20. Laboratory Diagnosis
Microscopic identification of eggs in stool or urine is the
most practical method for diagnosis.
Stool examination should be performed when infection
with S. mansoni or S. japonicum is suspected
urine examination should be performed if
S. haematobium is suspected
Treatment
Praziquantel: effective against all species
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21. Prevention and Control
Avoid contamination of water with the feces/urine of
man
Providing safe recreational bathing & swimming sites
Latrine construction and sanitary disposal of feces
and urine
Destroying snail hosts
Treatment of infected individuals
Health information dissemination
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22. Liver, Intestinal, and lung flukes
Liver, lung, and intestinal flukes:
 General characteristics :
 Transmission via food (infected fish, crabs, or water
vegetation)
 Hermaphrodities
 Flat ---leaf-like
 Redia and metacercaria (additional stages)
 Metacercaria infective stage
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23. Liver, Intestinal, and lung flukes
• The trematodes that infect liver, lung, and intestine are all
food-borne.
• Freshwater fish, crustaceans (crabs), and aquatic vegetation
are the sources of human infection.
Developmental stages :
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24. Cestodes
(Tape Worms)
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25. Cestodes (Tapeworms)
General characteristics:
Segmented, tape-like worms
Hermaphrodities
Size: from few mm to several meters
Obtains its nutrient by absorption through body
surface
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26. Morphology
The body is divided in to three main body regions:
Head (scolex) – attachment organ
Neck – growth region
Strobila – a collection of of proglottids
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27. Cestode (Tapeworm) Body Structure:
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28. Morphology…
a, Scolex (head)
b. Neck
c. Strobila made up of proglottids
(segments)
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29.  Cestodes of medically important include:
 Human infection with adult cestodes (intestinal cestodes):
oTaenia saginata (Beef tapeworm)
oTaenia solium (Pork tapeworm)
oHymenolepis nana (Dwarf tapeworm)
oHymenolepis diminuta (Rat tapeworm)
oDipylidium caninum (Dog tapeworm)
oDiphyllobothrium latum (fish tapeworm)
 Human infection with larval cestodes (Tissue cestodes):
oEchinococcus granulosus (Hydatid tapeworm)
oEchinococcus multilocularis
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30. 1. Taenia saginata
Common name: Beef tapeworm
Geographical distribution:
 Human infection with T. saginata occurs world wide
 very common in Ethiopia
Habitat
– Adult : in the small intesine of human
(4 -12 m long, ivory white color)
– Larvae: in muscular tissues of cattle
– Eggs: in faeces of human or in gravid segments
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31. T. Saginata morphology
- Scolex with 4suckers,
no hooks, no rostellum. - Proglottid(segement)
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32. Transmission and Life Cycle
Humans are the DH while cattle are the IH
The infective form for humans is cysticercus bovis
A person is infected with T. saginata after consuming raw or undercooked
beef containing cysticerci
In the small intestine the process of strobilization start & adult worm
forms.
Eggs are produced in the gravid segment of the worm
Cattle while grazing, ingest eggs along with their food
The ingested eggs hatch to liberate oncospheres in the animals intestine
The hooked oncospheres penetrate the mucosa to invade bloodstream
or lymphatic's to reach muscles of cattle
An oncosphere develop into cysticercus bovis
Cysticerci can develop anywhere in the animal’s body; the preferred
locations being striated muscles of hind limbs, diaphragm & tongue
When beef is consumed raw or undercooked by humans the life cycle
completes.
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33. Cont…
• Larval form of T. saginata is called cysticercus bovis.
(in bovine musculature, see below)
 It consists of a fluid filled sac, containing a small
invaginated scolex.
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34. Life Cycle
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35. Clinical features and pathology
 T. saginata infections are usually asymptomatic
 When the infection is symptomatic; vague abdominal
discomfort, nausea, weakness and weight loss may be
present.
 Very rarely migrating segments may cause appendicitis
or cholangitis
 Entanglement of worms may lead to intestinal
obstruction
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36. Laboratory Diagnosis
 Diagnosis of T. saginata infection is made by detection
of Eggs (microscopy)
 Demonstration of proglottids in feces
Treatment
Praziquantel or
Niclosamide
Prevention and control
Avoid eating raw or or insufficiently cooked meat
Cooking of beef at 560
C for 5 minutes will destroy
cysticerci
Proper sewage disposal prevents infection of cattle
Treating infected persons & providing health education
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37. 2. Hymenolepis nana
Distribution: occurs worlwide
Common name: Dwarf tapeworm
It is a common cestode infection of humans
More common in children
Organism Characteristics and Life Cycle
Hymenolepis nana exists in two forms, an adult and a
larval stage
Both the forms live in the human intestine
The adult worm lives in the small intestine. It is 2 to 4 cm
long. The smallest tapeworm known to infect humans.
The scolex has 4 suckers and rostellum with a single row
of hooklets
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38. Transmission and life cycle
Infection is acquired by ingestion of infective eggs
The oncosphrere is set free in the intestine
It penetrates the intestinal villi and transforms into a
cysticercoid larva
Larvae migrate back into the intestinal lumen, attach to the
mucosa, and mature into adult worm.
Eggs pass in feces to infect a new host. Eggs are infective when
passed in the feces.
Eggs can also hatch in the intestine of the same individual to
cause autoinfection (internal autoinfection)
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39. Hymenolepis nana (Dwarf Tape worm)
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40. Clinical features and pathology
Even with a large number of intestinal worms the
infection is usually asymptomatic
When symptomatic, patients have( especially children)
- anorexia, abdominal pain and
- diarrhoea
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41. Laboratory Diagnosis
H. nana infection is diagnosed by finding eggs in feces
Eggs of Hymenolepis nana
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42. Treatment
Praziquantel: the treatment of choice (acts against
both adult and larval forms of the parasite)
Niclosamide
Prevention and control
• Good personal hygiene and improved sanitation can
prevent the disease
• Health education
• Treatment of infected persons
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43. 3. Diphyllobothrium latum (fish tapeworm)
• Habitat:
• Adult- in the small intestine of man and fish-eating
animals
• Larval forms:
• Coracidium (1st
stage larva ) --------- in water
• Procercoid ( 2nd stage larva ) ------ in the body cavity of
Cyclops/ copepod (crustacean )
• Plerocercoid ( 3rd stage larva ) ----- in the fresh water fish
 Human Infection acquired by ingesting the infective stage,
plerocercoid in raw or undercooked fresh water fish.
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44. D. latum
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45. Developmental stages of Diphylobothrium latum
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46. Life cycle
• Immature eggs passed with in the feces of human.
• Eggs mature and yield oncospheres which develop into a coracidia.
• Coracidia ingested by a suitable freshwater crustacean (copepod 1st
IH),
develop into procercoid larvae .
• Ingestion of the copepod by 2nd
IH (small freshwater fish), the procercoid
larvae are released from the crustacean and migrate into the fish flesh,
develop into a plerocercoid larvae.
• After ingestion of the infected fish by the human host, the plerocercoid
develop into mature adult tapeworms which will reside in the small
intestine of human.
• The adults of D. latum attach to the intestinal mucosa by means of the
two bilateral groves (bothria) of their scolex .
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47. Clinical features and pathology
 Clinical symptoms may be mild, depending on the number
of worms
 Major symptoms:
 Abdominal pain
 Diarrhoea, constipation
 Weight loss, intestinal obstruction
 Eosinophilia
 As many as 40% of D. latum carriers may have low serum
levels of vitamin B12, presumably because of the
competition between the host and the worm for dietary
vitamin B12.
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48. Laboratory diagnosis
• Diagnosis of D. latum infection is made by the
recovery of eggs in human feces. ( microscopy)
Treatment
• praziquantel
Prevention and control
• Avoid eating raw, poorly cooked,or pickled fish
• Proper disposal of faeces
• Treatment of individuals and health education
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49. Human infection with larval cestodes
4. Echinococcus granulosus
 Common name: Hydatid worm
or minute tape worm of dog.
 In Ethiopia
 pastoral people in the South
and South-East of Ethiopia
 The smallest of all tapeworms (adult)
 Largest larval stage of all tapeworms
(Hydatid cyst)
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50. Habitat
Adult: small intestine of carnivores
such as dog, fox
Hydatid cyst/larvae: in the different body
parts (liver, lung, kidney, brain, etc) of human
and herbivorous animals (sheep)
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51. Cont…
The larval form of E. granulosus is the hydatid cyst
Hydatid cysts develop in tissues of the intermediate
host e.g. sheep, cattle, human..
The growth rate of hydatid cyst is 1 to 5 cm per year
hydatid cysts are filled with fluid (hydatid fluid) and
have a doubled layered covering.
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52. Life cycle of E.granulosus 52
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53. Clinical features and Pathology
The symptoms depend upon the location and
size of the hydatid cyst.
• Causes obstruction and pressure on vital
organs
The cyst grows slowly but continuously
The majority of hydatid cyst occur in the liver
Liver cysts cause obstructive jaundice
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54. Clinical …
• Cysts in the lungs may produce cough, dyspnea
and chest pain. Cyst rupture can lead to pulmonary
abscesses
• Large abdominal cysts ----- increasing discomfort
• Kidney cysts cause renal dysfunction
• Brain cysts produce intracranial pressure and
epilepsy
• In bones, the growing hydatid cyst leads to bone
erosion and pathological fractures.
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55. 55
Cont…
Group of Turkana people
waiting for an operation to
remove hydatid cysts.
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56. Laboratory diagnosis
Serological diagnosis – ELISA for Antibody detection
Examination of cystic fluid (for brood capsules and protoscolices) following
surgical removal of a cyst or fine needle aspiration
In symptomatic hydatid cyst: X-ray, CT scan, ultrasound studies are useful
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57. Treatment
Surgery is the main line of treatment in hydatid cyst disease
Albendazole
Puncture -Aspiration-Injection- Reaspiration (PAIR )
PAIR is minimally invasive and includes the following steps:
1. Under ultrasonographic guidance, percutaneous Puncture of
the cyst
2. Aspiration of 10 -15 ml of the cyst fluid
3. Injection of a parasitocidalsolution (95% ethanol ) in a
volume one-third the amount of fluid aspirated; and
4. Reaspiration of the fluid after 5 minutes
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58. Prevention and Control
 Proper personal hygiene
 Thorough washing of hands after handling dogs
 Periodic deworming of pet dogs
 Preventing dogs access to butchering site or offals of
infected animals is useful in controlling E. granulosus
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