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1. The
Schistosomes
The Blood fluke

2. Outline
– General feature of the blood fluke
– List of the blood flukes of medical importance
– For each species of blood flukes
• Geographical distribution
• Morphology and differential characteristics,
• Transmission and life Cycles,
• Laboratory diagnosis and
• Prevention and control

3. 1- A genus of Trematodes, Schistosoma, commonly known as blood-fluke, are parasitic
flatworms responsible for a highly significant group of infections in humans termed
schistosomiasis.
.
2- The sexes are separate (they are dioecious)
3- They reside in the blood vessels of the definitive host in their life cycles. Hence the
common name “Blood Flukes.”
4- Male worm has a split body called the gynecophoral canal. The female is usually found
within this canal “safe in the arms of her lover.” She leaves only during the egg laying period.
Males are broader and females are filiform and larger than male
General feature of the blood fluke

4. Snail hosts
The different species of Schistosoma have different types of snails serving as their intermediate
hosts; these hosts are as follows:
1- Biomphalaria for S. Mansoni ‫البولية‬ ‫المجاري‬ ‫بلهارسيا‬ ‫قوقع‬
.))
2
- Oncomelania for S. japonicum.
3- Bulinus for S. haematobium. ‫المستقيم‬ ‫بلهارسيا‬ ‫قوقع‬
)
Symptoms of schistosomiasis are caused by the body’s reaction to the worms’ eggs.
Intestinal schistosomiasis
1- abdominal pain,
2- diarrhoea
3- and blood in the stool.
4- Liver enlargement is common in advanced cases, and is frequently associated with an
accumulation of fluid in the peritoneal cavity and hypertension of the abdominal blood vessels.
In such cases there may also be enlargement of the
The classic sign of urogenital schistosomiasis is:
1-haematuria (blood in urine).
2- Fibrosis of the bladder and ureter,
3- and kidney damage.

5. Learning objective
• At the end of this section the student will be
able to
– Explain the general feature of blood fluke
– List the blood flukes of medical importance
– Explain the geographical distribution,
Morphology, differential characteristics,
transmission, life Cycles and pathogenesis of each
species
– Apply the necessary laboratory procedure for
detection and identification of the liver fluke

6. Blood fluke
• S. mansoni
• S. hematobium
• S. japonicum
• S. intrecalatum
• S. mekongi
• Animal schistosome
which occasionally
infect humans
– Schistosoma mattheel
– Schistosoma bovis
– Schistosoma rodhaini
– Schistosoma
margrebowiei

7. The Schistosomes
• General feature:
– They reside in the blood
vessels of the definitive host
in their life cycles. Hence
the common name “Blood
Flukes.”
– The sexes are separate (they
are dioecious)
– They are long cylindrical(~
20mm) and adopted to life in
blood vessel

8. • Male worm has a split body
called the gynecophoral
canal. The female is usually
found within this canal “safe
in the arms of her lover.”
She leaves only during the
egg laying period.
• Males are broader and
females are filiform and
larger than male

9. – Humans are the only or most significant host for
most of the species
– Snail host is required as intermediate host to
complete their life cycle
– There are no second intermediate hosts
– Reproduction takes in the sporocyst stage in the
snail.
– No redia and metacercariae stages
– Cercaria is the infective stage to humans in water
and the infective route is by skin
– egg without operculum, but with spine
– The eggs are main pathogenic stage.

10. Epidemology:
• Wide spread species
– Schistosoma mansoni causes intestinal schistosomiasis and
is prevalent in 52 countries and territories of Africa,
Caribbean, the Eastern Mediterranean and South America
– Schistosoma haematobium causes urinary schistosomiasis
and affects 54 countries in Africa and the Eastern
Mediterranean
– Schistosoma japonicum cause intestinal schistosomiasis
and are Common in parts of Japan, China, Taiwan,
Philippines, Thailand, and other parts of Southeast Asia
• Less wide spread species
– Schistosoma mekongi cause intestinal schistosomiasis and
are prevalent in 7 African countries and the Pacific region
– Schistosoma intercalatum is found in ten African countries

11. Distribution of Schistosomiasis

12. Life cycle

13. Transmissions

14. Life Cycle of Schistosoma spp.
• The eggs escape from
the body by penetrating
the walls of the veins
and small intestine or
urinary bladder (where
adults reside), and they
are passed in the feces
or urine. Example of a
Schistosoma mansoni egg

15. Life Cycle of Schistosoma spp.
Miracidium Swimming towards Snail Intermediate Host
• The eggs, if and when they reach fresh water,
will quickly hatch.
• The miracidium swims ceaselessly until
finds a snail host (die in 3-6 hours).

16. Life cycle in Snail
• After miracidum enters, the parasite goes through two
asexual developmental stages: mother and daughter
sporocysts.
• Mother sporocysts contain the daughters, which are
then released and found in the snail’s digestive and
reproductive organs.
• The daughter sporocysts hold the cercaiae,
• Continues producing sporocystes for up to seven
weeks within snail

17. Intermediate Hosts of Schistosoma spp.
S. mansoni only infect snails of the genus Biomphalaria.

18. Intermediate Hosts of Schistosoma spp.
S. japonicum are found in Oncomelania snails

19. Intermediate Hosts of Schistosoma spp.
S. haematobium persist in species of Bulinus.

20. Life cycle of Schistosoma spp.: Cercariae
• Cercaiae start to
emerge four
weeks after
penetration by
miracidium
• There is NO
second
intermediate
host

21. Life cycle of Schistosoma spp.: Cercariae
• Cercariae swim up and down in the water column until
finding host; without host die after three days.
• Move around and then enter and can disappear below surface
in 10 to 30 seconds, and into circulation system within 24
hours.

22. 5 Minutes after penetration of the human skin by cercaria,
the newly transformed schistosomule has penetrated the
outer layer of the epidermis, and is positioned just
beneath the skin.

23. 20 minutes after penetration of
the skin. Here the
schistosomule is migrating
through the dermis. This it will
do until it locates a blood
vessel. The schistosomule will
then break through into the
blood vessel, to be transported
in the circulatory system to the
heart and then the lungs.

24. Life cycle of
Schistosoma spp.: In
Human
• Various ways of migrating
through circulatory system
(heart, liver). End up in
veins draining liver where
they develop for three
weeks
• Pair up in these veins and
migrate to walls of guts or
bladder, depending on
species to produce eggs.

25. Adults can live 20
to 30 years!!

26. Life cycle of Schistosoma spp.: In
Human
• Species differences in Site Preferences of
Adults (male and female in copula)
– S. mansoni –veins of Large Intestine
– S. haematobium – veins of bladder
– S. japonicum – veins of small intestine

27. • The infective inhabitation of
Schistosoma in mesenteric
vein

28. Life cycle of Schistosoma spp.:
In Human
• Unusual in that eggs are the damaging
stage
– Traverse the walls of veins, tissues and mucosa
– Egg promotes growth of granuloma and this is
moved out into lumen of intestine or bladder where
expelled.

29. Granuloma of Schistosoma
2/3 of eggs remain in abdomen granuloma

31. Intestinal schistosomiasis
• Penetration of skin:- Penetration of of skin by
cercariae causes transient dermatitis
(swimmers' itch)
• Migratory phase - 4-10 weeks after infection.
– Is characterized by fever and toxic or allergic
reactions resulting from migration of immature
organisms.
– Often results in bronchitis, hepatomegaly,
splenomegaly, and diarrhea.

32. • Chronic phase - persons living in endemic
regions are often asymptotic.
– May have mild, chronic bloody stools or urine.
– Often have formation of granulomas.
Hepatomegaly, Spleenomegaly, Ascites
(accumulation of fluid in abdominal cavity
– Terminal stage is characterized by portal vein
hypertension syndrome, common saying, abdomen
distention looks like a big drum
– Ectopic lesion: The damage to the central nervous
system ( brain, spinal ) may cause paralysis
(monoplegia, hemiplegia ).

33. • 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.

34. abdomen distention looks like
a big drum, Ascites,
emaciation, varicosity, and
splenomegaly

35. abdomen distention looks like a big drum,
emaciation looks like a fire wood.

36. A patient of
schistosomiasis

39. Laboratory diagnosis
• Intestinal schistosomiasis
– Finding the eggs in faeces by direct examination or more
commonly by using concentration ;
– Mucus and blood are often present in the faecal specimen
1. Formol-ether conc. Tech
2. Formol detergent gravity sed tech
3. Kotho-katz technique
– Examining a rectal biopsy for eggs when they cannot be
found in faeces.
– occasionally eggs may also be found in urine often
following faecal contamination

40. Egg:S.mansoni
• Size : 114-17µm 45-68µm
• Shape: Oval, with one well
rounded pole and one more
conical pole
• Colour: pale yellow-brown
• Spine: large, triangular lateral
spine near the rounded end
• Shell: smooth, very thin
• Content: fully embryonated
(developed miracidium) when
discharged with the faeces

41. Egg: S japonicum
• Size: 70-80m
• Shape: oval, almost
round
• Colour: transparent or
pale-yellow
• Spine: very small hook-
like spine laterally
• Contain a fully
developed miracidium

42. • Ab-detection
– Immunodiagnosis using ELISA, RIA, Latex
`agglutination are helpful particularly in prepatent
period, and in chronic and ectopic cases in which
eggs are difficult to be demonstrated in the faeces.
• Ag-detection.
• EIA- detect circulating schistosoma antigens

43. Urinary schistosomiasis
• Finding eggs or occasionally the hatched miracidia in urine.
• Quantitative report is required, no of eggs/10ml urine
– Urine contains blood and appears red or red-brown and cloudy.
• Hematuria
• Protienuria
• Eosinphil
– Eggs may not be present in the urine all the time; it is neccessary to
examine urine collected over several days.
• Less frequently detecting eggs in faeces, rectal biopsy or
bladder mucosal biopsy when an infection is light.
• Immunodiagnosis: a variety of serodiagnostic methods are
currently available. These include: RIA, ELISA IHA.

44. Egg:S.hematobium
• Size : 120 - 170 µm by 40-70µm
• Shape: oval, with one well rounded
pole
• Spine : Terminal spine at one pole
• Shell: Smooth, very thin except minute
spines on the sucker
• Shell is not acid fast in Ziehl-Neelsen
staining, but the egg shell of other
terminally spined Schistosoma species
is acid fast
• Colour: pale yellow-brown
• Contain fully developed miracidium
when laid