Schistosoma Parasites

Adult Flukes live in blood vessels of infected Humans

S.haematobium S.mansoni S.japonicum

Called Blood Flukes

D.H: ManR.H: Rodent, Monkeys

D.H: ManR.H: Domestic animals

D.H: ManR.H: None

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Definitive Host Man Habitat

Superior & Inferior mesenteric plexus of

veins

Vesical & pelvic plexus of veins

Where adult S.mansoni live

Where adult S.haematobium live

Blood vessels

Inferior mesenteric plexus of

veinsWhere adult

S.japonicum liveRAAFAT T. MOHAMED

• Has separate sexes.• Lives in blood.• Has non-operculated eggs.• Has no Redia stage.• Has no encysted metacercaria. • Common species affecting man:• S. mansoni, S. haematobium, • S. japonicum, S. intercalatum and • S. mekongi.

Schistosoma differs from other trematodes in:

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Theodore Bilharz: discovered the worms and their relation to the disease in 1851 in Cairo.Manson: (1893):Discovered that there are 2 different species of the parasite in Egypt.

Leiper (1915- 1918): Discovered the relation to snail intermediate hosts and the mode of infection.

McDonagh (1918)Used tartar emetic for treatment

Recent discovery:

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Sexes: separateFemale: cylindricalMale: flattened, folded (gynaecophoric canal).

Suckers: oral & ventral (smaller in females).

Digestive system :

No muscular Pharynx Intestinal ceaca reunite in a single caecum.

Adult Morphology

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S. haematobium S. mansoni S. japonicum

10x 1 mm 8x1 mm 15xo.5 mm

3-5 testes in a line

6-9 testes in cluster

6-8 testes in a line

Fine tubercles course tubercles

No tubercles

Male

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FemaleS. haematobium S. mansoni S. japonicum

20x0.2 mm 14x0.15 mm 26x0.3 mm

Ovary post 1/3 ovary ant. 1/3 Ovary in the middle

Vit. gl. post 1/3 vit. gl post 2/3 Vit. gl. in post 1/2

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EggS. haematobium

S. mansoni S. japonicum

In urine In stool

Size 140x 60 150x60 85x65

Shape Ovalterminal spine

OvalLateral spine

OvoidMinute knob

Shell translucent, non operculated

Content Mature embryo (miracidium)

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Miracidium

S. mansoni

Biomphalaria alexandrina

Snail I. H

S. Haematobium

Bulinus truncatus

S. japonicum

Oncomelania

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Infective stage (Cercaria):

Formed of body and forked tail (furcocercous)

5-6 pairs of penetration glands.Skin penetration is aided by:

1-Proteolytic enzymes.2-Surface tension of drying

water.3-Movement of the tail

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Worms in their habitat

Female lays eggs

Eggs in urine or stools

Miracidia hatch

Miracidium infects snail i.h.

Cercarial shedding

Infection in contaminated

water

Schistosomulum reaches circulation

Worms mate in the liver

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Life cycle

S.mansoni live worm pair.mp4

Schistosoma Mansoni Miracidium inside the Egg.flv

Schistosoma Mansoni Penetrating Human Flesh!.mp4

WTDV027421.swf

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Development of Schistosoma inside the body of infected human

Cercariae penetrates human skin

Schistosomula

Venous circulationSystemic circulation

Liver

Portal vein

Vesical plexus

IIII

IV

II

Inf. mesenteric plexus

Aorta

♂♀

In urine or stoolDirection of venous blood flow

S.haematobium

S.mansoni

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Pathogenesis and Clinical Picture

There are 4 progressive stages:

I- Stage of invasion

Local dermatitis, irritation.

Papular rash.

(1-4 days)

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II- Stage of migration

By schistosomula

(3-4 weeks)

Metabolic products: toxic and allergic manifestations as

urticaria, fever, headache, muscle pain. In the lung: verminous pneumonitis, minute haemorrhage

cough, haemoptysis.

In the liver: enlarged and tender.RAAFAT T. MOHAMED

III- Stage of egg deposition and extrusion

The patient may complain of:

Generalized malaise, fever,

rigors, urticaria, abdominal pain

and liver tenderness.

A- Eggs are deposited in the venous plexus

Urticaria

(acute stage: 1-2 month)

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Katayama Syndrome

Blood vessel

Soluble egg antigens are released in blood stream

Occurs mainly in S.japonicum infection

1- ♀lays large number of eggs2- greater proximity to the liver

immune complex

Deposited in the tissues

Tissue damageThe patient suffers from:

Fever, chills, diarrhoea, generalized lymphadenopathy

Due to:

Thus also called acute toxoemic schistosomiasis

antibodies

Circulate

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B- Stage of egg extrusion:

Terminal haematuria, frequency of micturition, burning pain

Dysentery with blood and mucus in stool

In vesical & pelvic plexus of veins

Bladder wall

In mesenteric plexus of veins

Intestinal wall

Damage & haemorrhage

S.haematobium S.mansoni & S.japonicum

Eggs escape from the veins to the perivascular tissue due to:

1-Pressure within the venule2-Effect of the spine3-oozing lytic secretion of the miracidium within the egg

Egg extruded Egg extruded

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IV- Stage of tissue reaction (chronic stage)

Occurs around Schistosoma eggs deposited in various tissues.

Attract inflammatory cells

Deposition of fibrous tissue

Damage of affected organ and its fibrosis

Loss of its function

Egg shellmiracidium

Inflammatory cells

Shell & miracidial antigens

Delayed-type hypersensitivity

Granuloma formation in tissue

(months – years)

Granuloma develops

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Polyps in the colon in S.mansoni infection

hydroureter

hydronephrosis

Egg trapped in bladder wall

Fibrous tissue

Stone formation

In normal condition

In S.haematobium infection

Cancer bladder may occur

Normal mucosa of colon

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IV- Stage of tissue reaction (chronic stage)

In S.haematobium infection In S.mansoni infection

Eggs extruded in urine1

Eggs trapped in Bladder wall

2

Eggs fail to fix to venule wall are swept by

blood

3

Eggs trapped in Intestinal wall

Eggs extruded in stool

1

2

Eggs fail to fix to venule wall are swept by

blood

3

Cause Embolic lesions Cause Embolic lesions

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Embolic Lesions in the LiverPortal hypertension Hepatosplenomegaly

Oesophageal varicesAscites.

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Embolic Lesions in the lungPulmonary hypertensionBilharzial cor-pulmonale

Embolic lesions may occur in any other organ.

Cor-pulmonale = right-sided heart failure

Dilated right ventricle

Thickened wall

In Normal condition

In Schistosoma infection

Enlarged right ventricle

Trapped eggs

Means: enlargement of right ventricle due to high blood pressure in the arteries of the lung

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Diagnosis of Schistosomiasis

Clinically (suggestive)

Laboratory

1- Detection of eggs in urine or stool

3- Serological tests

2- Blood examination

Radiological imaging

Endoscopy

1- History of contact with infected water.2- Clinical picture according to stage of infection.

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I- Laboratory Diagnosis

1- Direct parasitological methods:- Detection of S.haematobium eggs in urine.

- Test for viability.

- Detection of S.mansoni eggs in stool by direct smear method or by concentration method.

- Kato thick faecal smear: for egg counting to assess the intensity of infection

- Rectal swab

S: 140X60 µ 150X60 µ

Oval, thin shellTerminal spine Lateral spineS:

C: Translucent C: Miracidium

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I- Laboratory Diagnosis

Eosinophilia, leucocytosis.

2- Blood examination:

3- Serological Tests:Detection of anti-Schistosoma antibodies or antigen in patient’s serum

a- IHAT (Indirect Haemagglutination test)

Latex particles

Sensitized sheep RBCs

+ve

-ve

(Immunodiagnostic Tests)

Anaemia due to

1- Egg extrusionIron deficiency anaemia

2- Hypersplenism Haemolytic anaemia

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b- ELISA (Enzyme-linked immunosorbent assay)

c- IFAT (Indirect Fluorescent Antibody test)

wash wash

wash wash washAb

detected

wash wash wash Ag detected

Coating with Schisto Ag

Coating with anti-Schisto

MAb

Schisto AgPatient serum

Ab detected

Patient’s serum

Ab linked to enzyme substrate

substratePatient’s serum

Ab linked to enzyme

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Calcified bladder with hydroureter

Intestinal affection

Stenosed ureters and

hydronephrosis

II- Radiological imaging

S.haematobium infection S.mansoni infection

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III- Endoscopyالمناظير

Cystoscopy in S.haematobium

Colonoscopy, sigmoidoscopy in S.mansoni

Done in chronic cases to detect lesions and take biopsies

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Treatment

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Praziquantel (Biltricide): For all schistosome species.Dose:40 mg/kg single oral dose

Oxamniquine (vancil):For S. mansoniDose: 30 mg/kg for 2 days

Metriphonate:For S. haematobium only. Dose: 10mg/kg every 2 weeks for 3

doses.

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Prevention and Control

- Mass treatment.

- Health Education.

- Snail control:

Physical methods

Biological methods

Chemical methods

X

Balanites aegyptica

Copper sulphate

Cercarial Dermatitis (Bather’s itch)

A condition that occurs due to penetration of cercariae of non-human species of schistosomes the skin of man.

Cercariae cannot go beyond the germinal layer.

Clinical picture:

Dermatitis, itching, oedema and secondary bacterial infection.

Treatment:

Antipruritics, antihistamincs,

antibiotics.RAAFAT T. MOHAMED

b- S.japonicum

b- Schistosomiasis mansoni

d- Fascioliasis

b- S.mansonid- non human schistosomes

Multiple Choice Questions

The major cause of morbidity in schistosomiasis is:a- Migration of adult worms against blood stream.b- Maturation of worms to adult stage in the liver.c- Occurrence of Embolic lesions.d- Deposition of eggs in tissues.

Kato technique is used to diagnose: a- Paragonimiasis

c- Schistosomiasis haematobium

Bather’s itch occurs frequently with:a- S.haematobium

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Katayama syndrome:

a- occurs most frequently in S.haematobium infection.

b- occurs most frequently in S.mansoni infection.

c- occurs most frequently in S.japonicum infection.

d- occurs in chronic schistosomiasis.

Multiple Choice Questions

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Give reasons for

Terminal haematuria is due to active deposition of eggs by adult female S. haematobium in vesical venous plexuses.

Eggs escape to the perivascular tissue and become extruded to the lumen of the urinary bladder.

Powerful contraction of the bladder at the end of micturition (to squeeze the last drops of urine) leads to haemorrhage (terminal haematuria).

Occurrence of terminal haematuria in S.haematobium infection

Egg passes lumen of urinary

bladderRAAFAT T. MOHAMED

Give reasons for

Many eggs that fail to be fixed to walls of venules are swept by blood to reach various organs

as the lungs where they form granulomas and fibrosis with obliteration of flow resulting in pulmonary hypertension and right-sided heart failure.

Occurrence of Bilharzial cor-pulmonale in schistosomiasis

Swept by blood

Lung Heart RAAFAT T. MOHAMED