TREMATODA Order: Strigeata
SCHISTOSOMA HAEMATOBIUM
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sm1-ic
Schistosoma spp: life cycle.
The human schistosomes (blood flukes) are digenic trematodes
of the superfamily Schistosomatoidea.
The adult worms inhabit the mesenteric veins
(S.mansoni, S.japonicum, S.mekongi, S.intercalatum)
or the veins of the vesical and pelvic plexuses (S.haematobium).
The life cycle is common to all species with a sexual generation
in vascular system of the definitive host and an asexual generation
in the intermediate hosts (snails).
1) Embrionated eggs are discharged in faeces and urine;
in water miracidia hatch from the egg and penetrate the intermediate hosts:
different genera of snails (see table)
The human schistosomes (blood flukes) are digenic trematodes
of the superfamily Schistosomatoidea.
The adult worms inhabit the mesenteric veins
(S.mansoni, S.japonicum, S.mekongi, S.intercalatum)
or the veins of the vesical and pelvic plexuses (S.haematobium).
The life cycle is common to all species with a sexual generation
in vascular system of the definitive host and an asexual generation
in the intermediate hosts (snails).
1) Embrionated eggs are discharged in faeces and urine;
in water miracidia hatch from the egg and penetrate the intermediate hosts:
different genera of snails (see table)
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| Miracidium |
mira1-ic
Schistosoma spp.: miracidium
Schistosoma spp.: miracidium
 |  |  |  |  |
| planorbis1 | Biomphalaria | Bulinus-ic | Bulinus | Onchomelania |
| planorbis1-ic | biom1-ic | Bulinus-ic | bul1 | sj5-ic |
S.mansoni: intermediate host of S. mansoni are snails
of the genus Biomphalaria (Planorbidae family).
S.haematobium: intermediate host of S.haematobium
are snails of the genus Bulinus
S.japonicum: intermediate host of S.japonicum are snails
of the genus Onchomelania, hupensis spp.
of the genus Biomphalaria (Planorbidae family).
S.haematobium: intermediate host of S.haematobium
are snails of the genus Bulinus
S.japonicum: intermediate host of S.japonicum are snails
of the genus Onchomelania, hupensis spp.
| Biomphalaria and Bulinus spp.: Courtesy of Bayer, from Bayer Manual of Pest Control |
| planorbis1 and Bulinus: Courtesy of Dr. Marc Lontie: Director of the laboratory of the Medisch Centrum voor Huisartsen, Maria Theresiastraat 63a; B-3000 Leuven, Belgium. |
| Schistosome species | Snails |
| S.mansoni | Biomphalaria spp. |
| S.haematobium | Bulinus spp. |
| S.intercalatum | Bulinus spp. |
| S.japonicum | Oncomelania spp. |
| S.mekongi | Neotricula spp. |
2) after penetration in the snail the miracidium develops into sporocysts and,
in about 4 weeks, thousend of cercariae are produced (asexual multiplication);
3) the infection of the definitive host occurs by penetration of the skin.
in about 4 weeks, thousend of cercariae are produced (asexual multiplication);
3) the infection of the definitive host occurs by penetration of the skin.
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| Typical transmission site | Contact water 1 | Contact water 2 | Contact water 3 |
 |  |  |
| Cercaria |
sp1-ic sp1a-ic sp2-ic
Cercaria sp1-ic: Schistosoma spp.: cercariae are the infective forms.
They measure about 500 micron. After encountering the skin,
the cercariae penetrate and lose the tail transforming into schistosomulae.
sp1a-ic: Cercaria of Schistosoma mansoni from snail.
During the penetration process the cercariae lose their tail
and transform into the larval stage: the schistosomulum
Cercaria sp1-ic: Schistosoma spp.: cercariae are the infective forms.
They measure about 500 micron. After encountering the skin,
the cercariae penetrate and lose the tail transforming into schistosomulae.
sp1a-ic: Cercaria of Schistosoma mansoni from snail.
During the penetration process the cercariae lose their tail
and transform into the larval stage: the schistosomulum
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| Schistosomulum | Eosinophils and schistosomulum |
schisto-ic eosi-ic
Schistosomulum
Schistosoma spp.: 1) schistosomulum; 2) antibody dependend cytotoxicity
to schistosomulum
4) after penetration schistosomula migrate to the lungs (in 3-4 days),
and after penetration in the pulmonary capillaries they are carried to
the systemic circulation and to the portal system.
In the hepatic circulation schistosomes mature to adult,
and in pairs they migrate to the mesenteric veins (S.japonicum and mansoni)
and to the vesical plexus (S.haematobium).
After 35 days (S.japonicum, S.mansoni) and 70 days (S.haematobium)
embryonated eggs are excreted in faeces and/or urine.
Control of schistosomiasis is difficult.
The control of snails is critical; environmental sanitation,
safety of supply water and education are essential.
Schistosomulum
Schistosoma spp.: 1) schistosomulum; 2) antibody dependend cytotoxicity
to schistosomulum
4) after penetration schistosomula migrate to the lungs (in 3-4 days),
and after penetration in the pulmonary capillaries they are carried to
the systemic circulation and to the portal system.
In the hepatic circulation schistosomes mature to adult,
and in pairs they migrate to the mesenteric veins (S.japonicum and mansoni)
and to the vesical plexus (S.haematobium).
After 35 days (S.japonicum, S.mansoni) and 70 days (S.haematobium)
embryonated eggs are excreted in faeces and/or urine.
Control of schistosomiasis is difficult.
The control of snails is critical; environmental sanitation,
safety of supply water and education are essential.
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| Collecting snails | Molluscisciding spraying | Molluscisciding drip feeding |
Schistosoma spp.: snail control with spraying and drip feeding.
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sh2-ic
S.haematobium: geographic distribution.
S.haematobium is reported from 54 countries in Africa.
S.haematobium is reported from 54 countries in Africa.
(Adapted and redrawn from: The Control of Schistosomiasis, WHO Technical Report Series, No. 830, 1994.) |
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sm2a-ic
S.haematobium: adult schistosomes live in pairs in the pelvic veins
(especially in the venous plexus surrounding the bladder);
males are 10-15 mm in lenght by 0,8-1 mm in diameter,
and have a ventral infolding from the ventral sucker
to the posterior end forming the gynecophoric canal.
Adult male with female in the copulatory groove.
(especially in the venous plexus surrounding the bladder);
males are 10-15 mm in lenght by 0,8-1 mm in diameter,
and have a ventral infolding from the ventral sucker
to the posterior end forming the gynecophoric canal.
Adult male with female in the copulatory groove.
sm2b-ic
Schistosoma haematobium: Females are slender ( 0,25 mm in diameter)
and longer (up to 20 mm in lenght),
and are held in the ginecophoric canal during copulation.
Each female lays about 150 eggs per day.
Adult male with female in the copulatory groove.
and longer (up to 20 mm in lenght),
and are held in the ginecophoric canal during copulation.
Each female lays about 150 eggs per day.
Adult male with female in the copulatory groove.
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| sh3-ic | shLon-ic |
Schistosoma haematobium: the diagnosis of urinary schistosomiasis requires
the identification of eggs in urinary sediment.
Eggs measure 115-185 by 40-70 µm and have a terminal spine;
viable eggs contain a motile miracidium. (Urine sediment).
the identification of eggs in urinary sediment.
Eggs measure 115-185 by 40-70 µm and have a terminal spine;
viable eggs contain a motile miracidium. (Urine sediment).
 |  |  |  |
| Schistosoma_4X-ic | Schistosoma_10X-ic | Schistosoma_20X-ic | Schistosoma_40X-ic |
S.haematobium:
Young men (35J) from Egypt with infertility and hematuria.
Schistosoma haematobium eggs are concentrated in the tissue of the bladder.
Young men (35J) from Egypt with infertility and hematuria.
Schistosoma haematobium eggs are concentrated in the tissue of the bladder.
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sh4-ic
Schistosoma haematobium: S.h. eggs can occasionally be found in faeces.
Eggs are the main agent of pathology inducing granuloma formation.
Eggs are the main agent of pathology inducing granuloma formation.
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sh5-ic
S.haematobium: bladder wall enlargement on echography.
Hyperplasia of the mucosa due to the presence of granuloma is the first finding;
fibrosis and calcification follow with polips formation in bladder and urether stenosis.
Hydronephrosis and possibly cancer are late complications of the infection..
Hyperplasia of the mucosa due to the presence of granuloma is the first finding;
fibrosis and calcification follow with polips formation in bladder and urether stenosis.
Hydronephrosis and possibly cancer are late complications of the infection..
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sh6-ic sh7-ic
S.haematobium: eggs of S.haematobium are not uncommonly
found in male genital organs,
but the significance of this finding has not yet been clarified.
The damage of the seminal vescicles seems to correlate
with the degree of the obstructive uropathy.
Less commonly affected are the prostate, the testes and the epididymis;
a relationship between the presence of eggs in seminal fluid
and male infertility has not been demonstrated.
S.haematobium: eggs of S.haematobium in seminal fluid.
found in male genital organs,
but the significance of this finding has not yet been clarified.
The damage of the seminal vescicles seems to correlate
with the degree of the obstructive uropathy.
Less commonly affected are the prostate, the testes and the epididymis;
a relationship between the presence of eggs in seminal fluid
and male infertility has not been demonstrated.
S.haematobium: eggs of S.haematobium in seminal fluid.
Courtesy of David Raymondo, MLT, CLS(m): Gamma-Dynacare Medical Laboratories, 1095 Carling Avenue, Suite 500; Ottawa, Ontario, Canada K1Y-4P6 |
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sh8-es-ic
Schistosoma haematobium: urine sediment, miracidium hatching
from the egg (400 X).
from the egg (400 X).
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sm8-ic
S.mansoni: different schistosome stages are used as antigen source
(cercariae, schistosomula, adults, eggs) for standard immunodiagnostic tests:
enzyme linked immunosorbent assay (ELISA), indirect immunofluorescence
test (IFAT), radioimmunoassay (RIA), indirect haemoagglutination (IHA),
circumovale precipitin assay.
Serological tests may be useful for travellers returning from endemic areas
and in patients with light or ectopic infection, with no detectable eggs in
the faeces, urine or intestinal biopsies (i.e. hepatic, CNS infections).
On the contrary, in patients living in endemic areas, the positive test may
reflect previous exposure to the agent rather than an active infection;
a slow decrease in titer after effective treatment is usually observed.
Recently, new tests for the detection of schistosome antigens
have been prepared using monoclonal antibodies.
The larval stage of S.mansoni used as antigen in the indirect fluorescence test.
From the Editor Pietro Caramello, MD
(cercariae, schistosomula, adults, eggs) for standard immunodiagnostic tests:
enzyme linked immunosorbent assay (ELISA), indirect immunofluorescence
test (IFAT), radioimmunoassay (RIA), indirect haemoagglutination (IHA),
circumovale precipitin assay.
Serological tests may be useful for travellers returning from endemic areas
and in patients with light or ectopic infection, with no detectable eggs in
the faeces, urine or intestinal biopsies (i.e. hepatic, CNS infections).
On the contrary, in patients living in endemic areas, the positive test may
reflect previous exposure to the agent rather than an active infection;
a slow decrease in titer after effective treatment is usually observed.
Recently, new tests for the detection of schistosome antigens
have been prepared using monoclonal antibodies.
The larval stage of S.mansoni used as antigen in the indirect fluorescence test.
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