S. Japonicum S.mekongi Report

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



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



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



Kingdom Animalia

Phylum Platyhelminthes

Class Trematoda

Subclass Digenea

Order Strigeiformes

Superfamily Schistosomatoidea

Family SchistosomatidaeGenus Schistosoma

Species japonicum



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



Ova

Broadly oval, 75-90 µm by 60-68 µm, have an

inconspicuous lateral spine, which may be

difficult to demonstrate



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



Adult female:

Longer, more slender (20 to 30 mm by 0.3mm)

Have oral and ventral suckers



Ova

70 to 90 microns by 50 to 65 microns

Have a spine (small knob-like projection)

Passed out with feces



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)



Identification of eggs in feces (with

sedimentation techniques)

Liver biopsy



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



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



Safe and effective drugs are available for the

treatment of schistosomiasis. The drug of

choice is praziquantel for infections caused

by all Schistosoma species.



Avoid direct contact with snail-infected

water

Protective clothing (use of rubber boots)

Proper disposal of human feces

Control of domestic animals and snails



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.



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.



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.



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.



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.



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.



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)



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.



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).



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.



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



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.

S. Japonicum S.mekongi Report

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