This document discusses Schistosoma, the parasite that causes schistosomiasis. It covers the morphology and life cycle of Schistosoma, which involves snail intermediate hosts and human definitive hosts. The clinical manifestations of schistosomiasis depend on the species and include symptoms caused by the body's immune response to eggs trapped in tissues. Schistosomiasis remains a major public health problem in many developing countries. Diagnosis is via identification of eggs in stool or urine samples, with praziquantel being the treatment of choice. Control relies on treating humans and reservoir hosts as well as reducing contact between people and infected waters.

1. Dr. Javaid Ali Gadahi
Associate Professor
Schistosoma

2. Schistosoma
General character:
Morphology
Reproduction system
Importance

3. History
 Once known as bilharzia. It was named after Theodor
Maximilian Bilharz.
 1st to describe the ailment in men in 1851 at the Kasr-el-Aini
in Cairo, Egypt.
 Schistosome eggs were found in ancient Chinese and
Egyptian mummies by Sir Armand Ruffer in 1910 (SRG).
 S. haematobium, first species to be discovered.
 S. japonicum, named by Fijiro Katsurada, Professor of
Medicine at Okayama Medical School.
 S. mansoni, discovered in 1907.
 S. mekongi, officially named in 1978.
 S. intercalatum, officially named in 1934.

4. Classification
• Phylum: Platyhelminthes (flatworms)
• Subclass: Digenea (alt. gen. seen in life cycle)
• Order: Strigeida
• Family: Schistosomatidae (blood flukes)
• Subfamily: Schistosomatinae
• Genus: Schistosoma
• Species: S. mansoni
S. japonicum
S. haematobium
S. indicum

5. Morphology
•Size: - Female 12 to 26 mm
- Male 6 to 22 mm
The three main species infecting
humans are
Schistosoma haematobium,
S. japonicum
S. mansoni .
Two other species, more localized
geographically, are S. mekongi
and S. intercalatum

6. Adult and larve of Sch.
Schistosomulum

7. Incidence
Species Geographical
distribution
Intestinal S. S. mansoni Africa, Middle East,
Caribbean, Brazil,
Venezuela, Suriname
S. japonicum China, Indonesia,
Philippines
S. mekongi Cambodia, Lao
S. intercalatum Rainforests of central
Africa
Urogenital S. S. haematobium Africa, Middle East
Mainly anyone in contact/sustained with infested waters.
ie. Farmers, women washing clothes, and
children

8. Geographic Distribution
• Schistosoma mansoni is found in parts of South
America and the Caribbean, Africa, and the
Middle East ;
• S. haematobium in Africa and the Middle East;
and
• S. japonicum in the Far East .
• Schistosoma mekongi and S. intercalatum are
found focally in Southeast Asia and central West
Africa, respectively .

9. Purple: S.mansoni
Blue: S.intercalatum
Orange: S. haematobium
Green: S. japonicum
Red: S. mekongi
Global
Epidemiology
Africa
Asia
South
America
Africa

10. Intermediate hosts
Different species of Schistosoma have different types of snails serving as
their intermediate host
1- Biomphalaria for S. Mansoni
2- Oncomelania for S. japonicum.
3- Bulinus for S. haematobium. ‫ا‬

11. Life Cycle

13. Life Cycle
(Eggslarvaeintosnail)
1. Parasite eggs released into freshwater
(from human urine, feces)
2. Eggs hatch  ciliated miracidia, free
swimming
3. Miracidia find & infect snail host
(different species prefer diff’t snail sp.)
4. Each miracidia transforms into many
fork-tailed, free swimming forms called
cercariae within 4-6 weeks of entering snail.
5. Cercariae leave snail and move into water at a rate of 1500/day for
up to 18 days.
Miracidia larva
with cilia

14. Life Cycle
(Intohumanlymphaticslungsliver)
6. Cercariae (bifurcated tail) find a human
host,
penetrate skin, and differentiate into
larval forms called schistosomulae.
7. Migrate through the host’s skin,
gain access to the lymphatic system.
8. Travel to the lungs (stay 3-8 days)
9. Migrate to liver portal system,
mature into male & female
adults
Cercariae with forked tail
schistosomulae

15. Life Cycle
(maturationmovementtotargetorganseggproduction)
10. In liver, m & f pair up  female inserts
herself into the gynecophoral canal of male
 they are now ‘paired’.
11. Migrate to favoured sites:
S. mansoni – mesenteric venules of
large bowel & rectum
S. japonicum – mesenteric veins of the
small intestine
S. haematobium – perivesical venous plexus
surrounding the bladder
Paired male & female

16. Life Cycle
(Eggrelease)
Females release eggs.
Egg characteristics
- Covered in microbarbs  cling to vascular
endothelium
- Pores, which allow the release of
1) Antigens
2) Enzymes (aid in passage of eggs
through host tissues)
Eggs enter lumen of excretory organs
50%  passed out of body
50%  trapped in tissues, carried away by
blood circulation, lymph.

17. Schistosomiasis is considered by the World Health Organization as
the second most socioeconomically devastating parasitic disease,
(after malaria), with hundreds of millions infected in a worldwide.

18. Pathogenesis
 Schistosomiasis is an immune disease
 All stages in host may be pathogenic: cercaria,
schistosomulae, egg and adult
 The main pathogenic factor is the egg
 Deposit in important organs – liver, intestine,etc
 Formation of egg granuloma
 Accumulation of eggs (thousands of eggs per day)
 Ectopic migration – brain, lung

20. Clinical Features
• Many infections are asymptomatic.
• Swimmer’s itch ( Cercarial Dermatitis)
• Acute schistosomiasis (Katayama's fever) may occur weeks after
the initial infection, especially by S. mansoni and S. japonicum.
• Manifestations include fever, cough, abdominal pain, diarrhea,
hepatospenomegaly, and eosinophilia.
• Occasionally central nervous system lesions occur:
cerebral granulomatous disease may be caused by ectopic S.
japonicum eggs in the brain,
Granulomatous lesions around ectopic eggs in the spinal cord
from S. mansoni and S. haematobium infections.

21. Clinical Features
Symptoms of schistosomiasis are caused by the body’s reaction
to the worms’ eggs.
• Intestinal schistosomiasis
• 1- abdominal pain,
• 2- diarrhoea
• 3- 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 spleen (hepatospenomegaly).
• Urogenital schistosomiasis is:
• 1-haematuria (blood in urine).
• 2- Fibrosis of the bladder and ureter,
• 3- and kidney damage.
• 4- Bladder cancer

22. Epidemiology of Schistomiasis

24. Cercarial Dermatitis

25. Immuno-pathologic
consequences
• 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 (S. haematobium) with hematuria, which can
progress to bladder cancer;
• pulmonary hypertension (S. mansoni ,S. japonicum ,more rarely S.
haematobium) ;glomerulonephritis; and central nervous system
lesions

26. Hepatomegaly & splenomegaly

27. Granuloma
( Sch. japonicum egg)

28. Granuloma
( Sch. hematobium egg)

29. Granuloma

30. Cellular reaction around eggs of
Schistosoma mansoni

31. 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.
Tissue biopsy (rectal biopsy for all species and biopsy of the
bladder for S. haematobium) may demonstrate eggs when stool
or urine examinations are negative .

32. Schistosoma egg
• JK
Sch. japonicum egg
Sch.mansoni egg
Sch. Haematobium
egg

33. Antibody detection
•
Antibody detection can be useful to indicate schistosome
infection in patients who have traveled in schistosomiasis
endemic areas and in whom eggs cannot be demonstrated in
fecal or urine specimens .

34. Treatment
•
Safe and effective drugs are available for the
treatment of schistosomiasis.
• The drug of choice is praziquantel for infections
caused by all Schistosoma species.
• Oxamniquine has been effective in treating
infections caused by S. mansoni in some areas in
which praziquantel is less effective .

35. Control methods
 Treat both human and the reservoir animals, such as
buffalo, swine etc ---praziquantel
 Feces (egg) control—avoid being discharged into water
 Snail control---molluscicides
 Ask people to avoid contacting with water that contained
the snails and cercariae