INTESTINAL (Helminths) AND LIVER PARASITES
TREMATODA Order: Strigeata

SCHISTOSOMA MANSONI

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)


 

Miracidium

mira1-ic

Schistosoma spp.: miracidium

planorbis1	Biomphalaria	Bulinus-ic	Bulinus	Onchomelania

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.

 

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.

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

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.

Collecting snails	Molluscisciding spraying	Molluscisciding drip feeding

Schistosoma spp.: snail control with spraying and drip feeding.

sm2-ic

S.mansoni: geographical distribution.
S.mansoni is endemic in 43 countries in Africa and occurs in the americas in Brazil,
Suriname, Venezuela and in the Caribbean.

sm2a-ic	sm2c-ic

sm2a: S.mansoni: adult schistosomes live in pairs
in the portal system and in the mesenteric venules;
males are shorter (7-12 mm in lenght and 2 mm wide)
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. 

sm2c: Adult male and female of S.mansoni.

sm2d-ic

 S.mansoni : Females are slender (1 mm in diameter) 
and longer (9-17 mm in lenght),
and are held in the ginecophoric canal during copulation.
Each female lays about 300 eggs per day.
Adult male with female in the copulatory groove. 
Adult of S.mansoni in mesenteric veins of hamster.

sm3-ic

S.mansoni egg: S.mansoni eggs measure 110-175 by 45-70 µm;
the colour is yellow, with a thin transparent shell and a strong lateral spine.
Fresh examination of intestinal biopsy with one egg in the mucosa.

sm4-ic

S.mansoni egg: viable eggs contain the motile larva, the miracidium.
After breaking the shell the ciliated miracidium moves in the water
and reaches the mollusca.
Fresh examination.

sm5-ic

S.mansoni egg: egg with typical spine in stools
(formol-ether concentration). Demonstration of eggs in faeces
and urine is the standard method of diagnosis of schistosomiasis.
Sensitivity of one stool examination does not exceed 60%.

sm6-ic

S.mansoni egg: lateral spine at higher magnification.
Other diagnostic methods include intestinal or liver biopsy.
Serology is useful in travellers from endemic areas before shedding
of eggs or in extraintestinal forms (spinal) but not in natives.

sm7-ic

sm7: S.mansoni: hepatosplenic schistosomiasis occurs in S.mansoni
and S.japonicum infections; it results by eggs embolization in hepatic venules
with formation of granulomas and portal fibrosis.
Epatosplenomegaly, bleeding oesophageal varices and hepatic insufficiency
are the more severe manifestations. Praziquantel is the drug of choice.
Liver biopsy: egg surrounded by granuloma and fibrosis of portal space. 

SM12_25X	SM13_25X	SM3_40X

SM4_10X	SM5_25X	SM8_25X	SM9_25X

S.mansoni: Cross-section of granulomas around eggs 
of Schistosoma mansoni observed in the appendix. 
Granulomas are composed of aggregation of mononuclear cells, 
neutrophils, lymphocites, plasmacells and fibroblasts; 
giant cells are also clearly visible in some sections (SM9_25X, SM12_25X). 
A newly deposited egg appears well preserved 
(SM4_10X, SM5_25X, SM3_40X). 
(H&E stain)

sh_01-HE-25X	sh_02-HE-25X	sh_04-HE-100X
sh_04-HE-250X	sh_05-HE-100X	sh_05-HE-250X

sh_07-HE-100X	sh_07-HE-250X	sh_08-HE-100X	sh_08-HE-250X

Shistosoma spp.: Cross-section of granulomas around eggs
of Schistosoma observed in the liver. Liver biopsy (20 gauge needle) from a 44 y.o. male Egyptian patient. Schistosoma eggs (ova) surrounded by granulomas and giant cell reaction. HE: Hematoxylin-Eosin stain and GM: Giemsa – May Gruenwald stain. Camera: LEICA DFC 320 DIGITAL CAMERA; Microscope: LEICA DMLB (TRINOCULAR).

sm7a-ic	sm7b-ic	sm7c-ic	10-hepa-ic	9-hepa-ic

sm7a: Polyposis due to S.mansoni infection. 
sm7b: Egyptian with splenomegaly due to infection with S.mansoni. 
sm7c: Brazilian with portal hypertension and ascites due to S.mansoni.
10-hepatosplenomegaly adult: Adult patient with severe hepatosplenomegaly
and ascites due to schistosoma mansoni
9-hepatosplenomegaly child: Ten year old girl with severe
hepatosplenomegaly due to schistosoma mansoni.

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.

INT...(Helminths)LIVER....