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8/8/2019 S. Japonicum S.mekongi Report
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Ova: female discharges ova into mesenteric venule ofdefinitive host; ova readily reach the liver; smaller sizeof the ova predisposes them to dissemination, especiallyto the brain and spinal cord
Miracidium: a free-swimming larva; once the ova isreleased into environment, miracidium hatches
immediately Sporocyst: a sac-like secondary larval stage; miracidium
transf
orms into a primary (mother) sporocyst;
Cercarium: an infectious form of Schistosoma whichinfects their hosts by direct skin penetration;
Schistosomulum: a tailless cercarium; after penetrationschistosomula migrate to the lungs (in 3-4 days),
Adult: adult worms can live for years; male and femaleare always hugged together; live primarily in thedistribution of the superior mesenteric vein
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Common name: Blood Fluke; Oriental Blood
Fluke
Causes disease that is clinically similar to
that of S.mansoni but often more seriousbecause more eggs (up to 10 times as many)
are produced by S.japonicum
Has been essentially eliminated from Japan,
although animal reservoirs still exist
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In 1847, Doctor Y. Fujii, who lived in
Katayama area, had reported the symptoms
of schistosomiasis in " Katayama - Report´
July 4, 1904: Dr. F. Katsurada discovered apair of adult SJ from a housecat named "
H ime (princess)´
In 1914, Dr. K. Miyairi discovered the
intermediate host
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Kingdom Animalia
Phylum Platyhelminthes
Class Trematoda
Subclass Digenea
Order Strigeiformes
Superfamily Schistosomatoidea
Family SchistosomatidaeGenus Schistosoma
Species japonicum
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Cercaria:
400-600 µm in length, and contain a pear-shapedhead and a forked tail
Infects hosts by direct skin penetration
Emerge daily from the snail host
Highly motile, alternating between vigorousupward movement and sinking
Attaches to human skin and secretes proteolytic
enzymes helping it to enter into cuteneouscapillary vessel; upon the penetration thecercarium sheds its tail and transforms intoschistosomulum
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Ova
Broadly oval, 75-90 µm by 60-68 µm, have an
inconspicuous lateral spine, which may be
difficult to demonstrate
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Adult male:
Shorter and sturdier (12-20 mm in length and 0.5
mm wide)
Has oral and ventral suckers Has 6 or 7 testes arranged in a row immediately
behind ventral suckers
Gynecophoral canal- groove on ventral surface
extending to posterior end where the male holds
the female
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Adult female:
Longer, more slender (20 to 30 mm by 0.3mm)
Have oral and ventral suckers
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Ova
70 to 90 microns by 50 to 65 microns
Have a spine (small knob-like projection)
Passed out with feces
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Mainly by contact with contaminated water.
Infective free-swimming larval forms
(cercariae) penetrate directly through the
skinNot directly transmitted from person-to-
person; infective person will release eggs in
feces; infective snails will release cercariae
as long as they live (several weeks to 3months)
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Identification of eggs in feces (with
sedimentation techniques)
Liver biopsy
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Disease: Oriental schistosomiasis
Chronic pathology Hepatic schistosomiasis and hepatosplenic
schistosomiasis (S. mansoni, S. japonicum); Ectopic
("displaced") schistosomiasis; Neuroschistosomiasis(S. japonicum, S. haematobium)
Acute schistosomiasis (Katayama's fever) mayoccur weeks after the initial infection: fever, cough, abdominal pain, diarrhea,
hepatosplenomegaly, andeosinophilia. Occasionally central nervoussystem lesions occur: cerebral granulomatousdisease may be caused by ectopic S. japonicumeggs in the brain
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S. japonicum is found China, Japan, the
Philippines and Indonesia; an estimated 500-
600 million people are infected in 75
countries Endemic in the Philippines:
Sorsogon, Oriental Mindoro, Samar, Leyte, Bohol,
provinces of Mindanao
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Safe and effective drugs are available for the
treatment of schistosomiasis. The drug of
choice is praziquantel for infections caused
by all Schistosoma species.
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Avoid direct contact with snail-infected
water
Protective clothing (use of rubber boots)
Proper disposal of human feces
Control of domestic animals and snails
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Parasitic blood-fluke (also called Mekong
Schistosome) found exclusively in the Mekong
river basin of Laos and Cambodia in South-
east Asia.The adult worms feed on nutrients found in
the blood; globulins and red blood cells,
through anaerobic glycolysis, thus depriving
the host of these nutrients.
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Def initive host: Humans (causes damage to
the liver, spleen, gastrointestinal tract, and
esophagus)
Intermediate host: N eotricula aperta snail,which is the origin of the name for the
disease, ´snail fever.
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S. mekongi cases were first reported in 1957
in Laos and 1968 in Cambodia. Due to many
similar characteristics with the close relative
S. japonicum, S. mekongi was first identifiedas a unique species in 1978.
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Adult worms are dioecious, where males andfemales are morphologically different.
Male worms can grow up to 2.2 cm, whilefemales grow up to 2.6 cm. Adults have both an
oral and ventral sucker which attaches to thevenous wall, preventing blood flow fromdislodging the parasite.
The worms are an off-white color, and the malepossesses a gynecophoric channel; a troughrunning laterally in which the female rests. Thisis known as eternal copulation, and is mostcommonly found in the mesenteric venousplexus.
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Nearly spherical embyronated
eggs by the mating worms are
smaller compared to Schistosoma
japonicum, with diminutive spine
on the lateral axis.
About 100 eggs per day, lower
than other schistosomes; S.
japonicum (>200 eggs per day)
Small and lacking a pronouncedspine, facilitates circulation.
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Cercarium are thelarval stage infectiousto humans, and aremorphologically
distinct from theother larval stagesbased on theirbifurcated tail andthe presence of
embryonic suckersused to attach andpenetrate the humanhost.
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Infection is verified by the
presence of eggs in stool
samples. S. mekongi eggs are
differentiated from those of S.japonicum based on size. S.
mekongi eggs are smaller (60-
70 m by 52-61 µm) than eggs
of S. japonicum (75-90 µm by
60-68 µm)
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S. mekongi infection hasalso been called MekongSchistosomiasis.
Though similar to S.japonicum, the clinicalpresentation of diseasedue to S. mekongi ismilder. Acute pathologyincludes a rash at the site
of penetration of the skin,known as cercarialdermatitis or swimmers·itch.
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Single dose of the anti-parasitic drug
praziquantel, delivered at 40 mg/kg (15), for
clearing the infection via paralysis of worms and
destruction of the tegument encasing the worm.
The drug is ineffective at killing either eggs or
immature worms. There is no treatment for the
scarring that the eggs can cause, but reducing
the production of eggs through the elimination
of mating worms will limit further cirrhosis. A single dose of praziquantel is 70-100% effective
at eliminating all egg excretion in 4-6 weeks (4).
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Abstract
Twelve Israeli travelers acquired
schistosomiasis in Laos during 2002²2008, and
7 of them had acute schistosomiasis. Thepatients were probably exposed to
Schistosoma mekongi in southern Laos, an
area known to be endemic for
schistosomiasis. Four possibly were infected
in northern Laos, where reports of
schistosomiasis are rare.
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Morphology of ova (size and spine)
S. japonicum: bigger with spine
S. mekongi: smaller and lacks distinct spine
Intermediate host S. japonicum: Onchomelania hupensis
S. mekongi: Neotricula aperta
Location inside the human host
S. japonicum: commonly found in mesenteric
veins draining the small intestine
S. mekongi: bloodstream
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Egg-laying capacity
S. japonicum: 12 times per day with 100 to 300
ova
S. mekongi: almost 100 eggs per egg-layingVirulence of disease caused
S. japonicum-caused disease is more virulent.
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