1. Schistosoma
Dr. R. Someshwaran, MD., Assistant professor,
Department of Microbiology,
Karpagam faculty of Medical Sciences & Research
2. Objective of today’s class
• To define the General features,
Species and life cycle of Genus
Schistosoma
• To elucidate briefly on the clinical
spectrum, lab diagnosis and
management of Schistosomiasis.
4. Unlike trematodes
Schistosoma has only one intermediate host.
No reservoir.
Schistosoma eggs bile stained and not operculated .
Forked tail cercaria (Infective form).
Cylindrical worm (Not flat – leaf like).
Only trematode in which sex is separated while other
trematodes are hermaphrodite (Monoecious)
5. INTRODUCTION
• Geographic distributions:
• Schistosoma hematobium - Africa,
• Schistosoma mansoni - Africa and America
• Schistosoma japonicum - Far East Asia, Some
parts of Africa
• Epidemiology
Approximately 250 million people are infected
with schistosomes and 600 million are at risk.
8. Morphology
• Adult worms are 10 to
20 mm long
• Schistosomes have
separate sexes
• the male has a canal in
which the slender
female worm resides
9. The eggs are very characteristic and confirm diagnosis.
• S. mansoni eggs in feces
have a spine on the side
• S. hematobium eggs in
urine have an apical spine
• S. japonicum eggs are more
round with a vague spine on
the side.
10. Schistosoma
haematobium
Schistosoma
mansoni
Diagnostic
Diagnostic
Stage:
Stage:
Eggs in urine Eggs in stool
Infective Stage:
Infective Stage: Forked tailed Cercaria swimming in fresh
water
Mode of
Mode of
infection:
infection:
• Cercaria penetrates human skin upon exposure
to fresh water containing cercaria & cause
itching at site of penetration.
• After 2-3 weeks of infection, fever, chills and
diarrhoea occurs due to presence of the
Schistosoma larva in blood, which migrate to the
liver venules.
13. • Definitive host for Schistosoma spp., is Man
• Dogs, cats, rodents, pigs, hourse and goats,
serve as Reservoir host for S. Japonicum
14. The cercariae
• Man is infected by fork
tailed cercaria in fresh
water by skin penetration
• The cercaria travel through
the venous circulation to the
heart, lungs and portal
circulation
• They mature and reach:
• the mesenteric veins (S.
japonicum and S. mansoni)
• The bladder vessels (S.
hematobium) where they live
and ovulate for the duration
of the host's life.
15. Infective Stage
Schistosoma cercaria (forked tail).
Found in fresh water.
Penetrate the skin of human upon contact with
water containing it.
17. Sites for localization
• S. japonicum - Superior mesenteric veins
draining the small intestine
• S. Mansoni - Superior mesenteric veins
draining the large intestine
• S. Haematobium - Venous plexus of bladder, it
can also be found in the rectal venules
27. Pathology of schistosomiasis
• S. mansoni and S. japonicum includes:
• Katayama fever, periportal fibrosis, portal
hypertension, and embolic egg granulomas in
brain or spinal cord.
• S. haematobium includes: hematuria,
calcification, squamous cell carcinoma, and
occasional embolic egg granulomas in brain or
spinal cord.
28. Pathology of Schistosomiasis
• Schistosoma haematobium
Causes urinary schistosomiasis
1. PREPATENT PERIOD 10-12 wks
2. EGG DEPOSITION AND EXTRUSION:
1. painless haematuria
2. Inflammation of bladder and burning
micturition
3. TISSUE PROLIFERATION AND REPAIR:
• Fibrosis , papillomata in the bladder
and lower ureter leading to
obstructive uropathy.
• Periportal fibrosis
• Lung and CNS involvement
• Schistosoma mansoni
Causes intestinal schistosomiasis
1. PREPATENT PERIOD 5-7 wks
2. EGG DEPOSITION AND
EXTRUSION:
1. dysentery (blood and mucus in
stools),
2. hepatomegaly splenomegaly
3. TISSUE PROLIFERATION AND
REPAIR:Fibrosis ,
• Papillomata in intestine,
• Pperiportal fibrosis,hematemesis
• Lung and CNS involvement.
29. Schistosomiasis or bilharzia
• Disease affecting many people in developing
countries.
• ‘Acute schistosomiasis’ - snail fever and
cutaneous schistosomiasis.
• Low mortality rate, schistosomiasis can also
be very debilitating.
• Bilharzia, or bilharziosis, is named after
Theodor Bilharz, who first described the
cause of urinary schistosomiasis in 1851.
30. A 13-year-old boy with
schistosomiasis
• Hepatosplenomegaly,
• ascites,
• muscle atrophy,
• anaemia,
• diarrhea
• haemorrhage from the
gastrointestinal tract
33. Diagnostic Stage
* Schistosoma mansoni:-
- Eggs found in stool of intestinal Schistosomiasis
patients.
- Oval egg with lateral spine.
34.
35. Management
• Contaminated water should be avoided
• Sanitary disposal of sewage
• Prevent the contamination of water by feces
and urine
• Destruction of snails
• Treat the patients
• No vaccine is available
• Praziquantel is effective against all species
37. Drugs used in elimination of worms
(Praziquantel)
Drug of choice for all Trematodes & Cestodes except
Fasciola species & hydated sand.
The nervous system of Trematodes and Cestodes is
not completely studied. However Praziquantel was
found to increase the calcium ion influx inside the
worm muscle causing prolonged spasms for the
worm; leading to spastic paralysis & death of the
worm.
This action not observed on Nematodes, insects or
mammalians.
38. Take home message
• Schistosoma – Blood flukes
• Fork tailed cercaria – Infective form
• Not metacercariae unlike Typical trematodes
• Bile stained eggs
• Schistosoma hamtobium – Terminal spine
• Schistosoma mansoni – Lateral spine
• Schistosoma japonicum – Lateral knob
• Biharrziasis – Treat with Praziquantel
