البوم لبويضات ال Schistosoma

Schistosoma
mansoni

Schistosoma
mansoni eggs.

Schistosoma mansoni eggs are large
(114 to 180 µm long by 45-70 µm wide) and have a characteristic shape,
with a prominent lateral spine near the posterior end. The
anterior end is tapered and slightly curved. When the eggs are
excreted in stool, they contain a mature miracidium.


A	B

A, B: Eggs of S.
mansoni in unstained wet mounts. Images courtesy of the
Wisconsin State Laboratory of Hygiene.


C	D

C, D: Eggs of S.
mansoni in unstained wet mounts. Images courtesy of the
Missouri State Public Health Laboratory.


E	F

E, F: Eggs of S.
mansoni in unstained wet mounts.

Schistosoma mansoni adults.

Adults of Schistosoma mansoni.
Unlike the flukes, adult schistosomes have the sexes separate, with the
female residing in a gynecophoral canal within the male. Male
worms are robust, tuberculate and measure 6-12 mm in length. Females are
longer (7-17 mm in length) and slender. Adult S. mansoni
reside in the venous plexuses of the colon and lower ileum and in the
portal system of the liver of their host.


A	B

A, B: Adults of S.
mansoni. The thin female resides in the gynecophoral canal of
the thicker male. Note the tuberculate exterior of the male in
Figure B.

Life cycle
of Schistosoma spp

البوم لبويضات ال Schistosoma Schistomes_LifeCycle

Eggs are
eliminated with feces or urine
.
Under optimal conditions the eggs hatch and
release miracidia
, which swim and penetrate specific snail intermediate
hosts
.
The stages
in the snail include 2 generations of sporocysts

and the production of cercariae
. Upon
release from the snail, the infective cercariae swim, penetrate the skin of the human
host
,
and shed their forked tail, becoming schistosomulae
.
The schistosomulae migrate through several tissues and stages to their residence in the
veins (,
).
Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each
species
.
For instance, S. japonicum is more frequently found in the superior mesenteric
veins draining the small intestine
,
and S. mansoni occurs more often in the superior mesenteric veins
draining the large intestine
.
However, both species can occupy either location, and they are capable of moving between
sites, so it is not possible to state unequivocally that one species only occurs in one location.
S. haematobium most often occurs in the venous plexus of bladder
, but it can also be found in
the rectal
venules.
The females (size 7 to 20 mm; males slightly
smaller) deposit eggs in the small venules of the portal and
perivesical systems.
The eggs are moved progressively toward the lumen of the intestine (S. mansoni and S.
japonicum) and of the bladder and ureters (S. haematobium), and are
eliminated with feces or urine, respectively
. Pathology of
S. mansoni and S. japonicum schistosomiasis includes: Katayama fever, presinusoidal egg granulomas, Symmers’ pipe stem periportal fibrosis,
portal hypertension, and occasional embolic egg granulomas in brain or spinal cord.
Pathology of S. haematobium
schistosomiasis includes: hematuria, scarring, calcification, squamous
cell carcinoma, and occasional embolic egg granulomas in brain or
spinal cord.

Human contact with water is
thus necessary for infection by schistosomes. Various animals, such as
dogs, cats, rodents, pigs, hourse and goats, serve as reservoirs for S.
japonicum, and dogs for S. mekongi.

Schistosoma
haematobium

Schistosoma
haematobium eggs.

The eggs of Schistosoma haematobium
are large (110-170 µm long by 40-70 µm wide) and bear a conspicuous
terminal spine. Eggs contain a mature miracidium when shed in
urine.


A	B

A, B: Eggs of S.
haematobium in wet mounts of urine concentrates, showing the
characteristic terminal spine.

C

C: Egg of S. haematobium
in a wet mount of a urine concentrate.

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