Schistosoma Species PDF

Schistosoma species by Dr. Shaimaa Helmy Ass. Professor of Medical parasitology Acting Head of Parasitology Department Faculty of Medicine Helwan University  Objectives By the end of this lecture, you will be able to: Rec...

Schistosoma species by Dr. Shaimaa Helmy Ass. Professor of Medical parasitology Acting Head of Parasitology Department Faculty of Medicine Helwan University  Objectives By the end of this lecture, you will be able to: Recognize Schistosoma species regarding its: Geographical distribution Life cycle Mode of infection Pathogenesis Clinical picture Diagnosis Treatment Prevention and control Define cercarial dermatitis  Schistosoma spp. Blood flukes Schist= split ; soma=body (Schistosomes, Bilharzia) Schistosoma mansoni & Gynecophoric canal Schistosoma japonicum (Intestinal bilharziasis) Schistosoma haematobium (Urinary bilharziasis) Geographical Distribution of Schistosoma Species Schistosoma mansoni Schistosoma japonicum Schistosoma haematobium  Habitat Adult Flukes live in blood vessels of infected man Inferior & Superior mesenteric plexus S. japonicum of veins Inferior mesenteric S. mansoni Vesical & pelvic plexus of veins plexus of veins S. haematobium  Life Cycle of Schistosoma Infected Man (DH) Mode of infection Skin penetration by furcocercous cercaria from contaminated canal water. Habitat (venous plexus) Egg (DS) Fresh water Furco-cercous cercaria (IS) Snails (IH) Bulinus Biomphalaria Onchomelania truncatus  Mode of Infection Skin penetration by furcocercous cercaria from contaminated canal water. HOW?? - Surface tension of drying droplets of water. - Proteolytic enzymes secreted by penetration glands. - Strong lashing movement of the tail pressing the body of the cercaria into the skin.  Development of Schistosoma inside the body of infected human III II IV Schistosomulum I Furco-cercus cercaria Infective stage Eggs Diagnostic stage Development of Schistosoma inside the body of infected human (cont.)  Pathogenesis and Clinical Picture There are 4 progressive stages: I- Stage of invasion (1-4 days) Local dermatitis, irritation. Papular rash.  II- Stage of migration [3-4 weeks] Metabolic products: toxic and allergic manifestations as urticaria, fever, headache, muscle pain. Liver Lung verminous enlarged and tender pneumonitis, minute haemorrhage cough, haemoptysis  III- Stage of egg deposition and extrusion (acute stage) [1-2 month] A- Eggs are deposited in the venous plexus Release of soluble egg antigens in the circulation The patient may complain of: Generalized malaise, fever. Rigors, urticaria, abdominal pain and liver tenderness. Acute toxoemic schistosomiasis (Katayama Syndrome) Occurs mainly in S. japonicum infection lays large number of eggs & greater proximity to the liver Soluble egg antigens are released in blood stream Immunoglobulins production immune complex Circulate Deposit in the tissues Complement stimulation Fever, chills, diarrhoea, MAC generalized lymphadenopathy Tissue damage  B- Stage of egg extrusion Eggs escape from the veins to the perivascular tissue due to: 1-Pressure within the venule 2-Effect of the spine Damage & haemorrhage 3- Lytic secretion of the miracidium within the egg  B- Stage of egg extrusion (cont.) Blood Vessel Blood Vessel Intestinal wall in S. mansoni Bladder wall in S. & japonicum heamatobium Intestinal lumen bladder lumen Egg extruded Egg extruded in stool in urine Dysentery with blood and Terminal haematuria, frequency of mucus in stool micturition, burning pain  IV- Stage of tissue reaction (chronic stage) Tissue reaction occurs around Schistosoma eggs deposited in tissues Granuloma Formation This takes (months – years) Shell & miracidial antigens Attract inflammatory cells Deposition of fibrous tissue Damage of affected organ and its fibrosis Loss of its function  IV- Stage of tissue reaction (chronic stage) cont. In S. mansoni & japonicum Normal mucosa of colon Fibrous thickening and Colonic Polyps stenosis Sandy patches  IV- Stage of tissue reaction (chronic stage) cont. In S. haematobium hydroureter Stone formation Bladder cancer may occur IV- Stage of tissue reaction (chronic stage) cont. Eggs fail to fix 3 to venule wall are swept by blood Eggs trapped in 2 Intestinal wall & bladder wall 1inEggs extruded stool &urine Cause Embolic lesions  Embolic Lesions in the Liver Oesophageal varices Portal hypertension  Embolic Lesions in the Liver Hepatosplenomegaly Ascites.  Embolic Lesions in the lung Schistosoma eggs that fail to fix to venule wall are swept by blood to reach pulmonary capillaries Pulmonary arteriolitis Pulmonary hypertension Trapped Enlargement of right side of the heart eggs Congestive heart failure = Cor-pulmonale Enlarged right ventricle [Bilharzial Cor-pulmonale]  Diagnosis of Schistosomiasis (A) Clinically 1- History of contact with infected water. 2- Clinical picture according to stage of infection. (B) Laboratory (C) Radiological imaging (D) Endoscopy  (B) Laboratory Diagnosis 1- Stool & Urine Examination: Detection eggs in stool & Urine In S. Haematobium: Last drops after 15 min of physical exercise In S. mansoni: Kato thick faecal smear: for egg counting to assess the intensity of infection - Rectal swab S. Haematobium haematobium S: 150X60 µ S. mansoni 140X60 µ S: Oval, thin shell , lateral spine With terminal spine C: Translucent C: Miracidium  (B)Laboratory Diagnosis cont. 2- Serological Tests: (Immunodiagnostic Tests) Detection of antibodies or antigen in patient’s serum by: - ELISA (Enzyme-linked immunosorbent assay) - IHAT (Indirect Haemagglutination test) - IFAT (Indirect Fluorescent Antibody test)  (B)Laboratory Diagnosis cont. 3- Blood examination: Anaemia due to ❑ Iron deficiency anaemia: a- Blood loss: dysentery, varices, hemorrhoids & melena c- bleeding tendency due to liver cell failure ❑ Haemolytic anaemia: due to Hypersplenism Eosinophilia leucocytosis.  (C)Radiological imaging X- Ray Calcified bladder Stenosed ureters and colonic with hydroureter hydronephrosis affection  (D)Endoscopy Cystoscopy in Colonoscopy, sigmoidoscopy in S. mansoni S. haematobium Done in chronic cases to detect lesions and take biopsies  Treatment Praziquantel Prevention and Control - Mass treatment. - Health Education. - Snail control.  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.