2. Schistosomes
Professor Dr. Azza El-Ghareeb

3. Differences between Schistosomes and other
Trematodes
Cylindrical ♀
Scistosomes are NOT hermaphrodite
(sexes are separate).
Male is flat and female is cylindrical.
Eggs are NOT operculated but have a spine.
Inside the snail: NO redia stage.
Infective stage: Cercaria NOT encysted metacercaria.
Mode of infection: skin penetration NOT by ingestion.
Flat ♂
Inside snail
miracidium
operculum
S.haematobium
S.mansoni
sporocyst
redia
Heterophyes
Fasciola
Cercaria
spine

10. Forked cercaria of Schistosoma
  Cercaria is the infective stage. It is composed of the body and forked tail (including tail stem and fork) and has pairs of penetrating glands in the body.

13. Mode of infection
Skin penetration by cercaria from contaminated water of canals aided by:-
1- Surface tension of drying droplets of water.
Proteolytic enzymes secreted by penetration glands.
Strong lashing movement of the tail pressing the body of cercaria into human skin

14. People are at risk of infection due to agricultural, domestic and recreational activities which expose them to infested water

18. Eggs pass into the perivascular tissue of the urogenital system and finally to the lumen of the urinary bladder ( in case of $. haematobium) and then pass in urine. Eggs do not hatch in urine, except when it is diluted with fresh water.
In case of $.mansoni the female is carried in gynaecophoric canal of male and pass against the blood stream but through the inferior mesenteric veins to rectum, sigmoid and descending colon peripheral venules.
Eggs pass to the lumen of the bowel, reach external environment with feces.

20. SCHISTOSOMA HAEMATOBIUM
Pathogenesis
1) Stage of invasion
Cercarial dermatitis occur
2) Stage of migration
Lung: verminous pneumonitis, cough, sputum & haemoptysis.
Liver & spleen: hepatosplenomegaly.
Toxic & allergic manifestations: by metabolic products of worms e.g., fever, headache, muscle pain and eosinophilia.

21. 3) Stage of egg deposition = Acute stage = open lesion
Terminal haematuria: contraction of bladder during micturition leads to injury of venules by egg spines leading to passage of blood in urine.
Polyuria, urgency and frequency of micturition due to inflammation.

22. 4) Stage of tissue fibrosis = chronic stage = [complications of urinary bilharziasis]
Kidney: hydronephrosis, pyonephrosis, renal failure.
Ureter: stricture and hydroureter.
Bladder: polyp, ulcer, sandy patches, contracted, calcified and cancer.
Urethra: fistula and stricture.
Genital organs: 1/ pseudo elephantiasis of penis
2/ granuloma in prostate, seminal vesicle, ovary and uterus.

23. Bilharzial corpulmonale
Schistosoma eggs that fail to fix to venule wall are swept by blood to reach pulmonary capillaries leads to:
1- Granuloma formation around the eggs and fibrosis.
2- Obliteration of pulmonary arterioles.
Cause pulmonary hypertension that leads to Rt ventricle hypertrophy leading to Rt sided heart failure.

24. Clinical picture
a- In endemic area: haematuria, dysuria, urgency and frequency.
b- In mild infection: haematuria manifested after muscular activity.
c- Infection of seminal vesicle manifest by blood in seminal fluid

25. Diagnosis

26. I- Signs & symptoms of the disease. II- Laboratory.
1- Direct a) In acute cases [when egg can be detected easily in urine]
Examination of last drop of urine for detection of egg.
b) In chronic cases [when egg cannot be detected in urine]
Biopsy from mucosa of urinary bladder for detection of eggs and histopathological lesion of schistosomiasis

27. c) Chemical reagent strips for detecting haematuria: Positive result is interpreted as indicating of active infection in endemic areas.

28. 2- Indirect (Serodiagnosis)
Diagnostic techniques: (still positive for a period after cure)
a- Indirect haemagglutination test (IHAT).
b- Enzyme linked immunosorbent assay (ELISA).

29. III. Radiology: it can detect bladder and ureteral changes.
a- X-ray.
b- Ultrasonography: It is non-invasive, simple, and portable and has no biological hazards to the patient or operator. It can be used for grading hydronephrosis, renal and urinary bladder wall lesions.

30. Bilharzial corpulmonale

31. IV- Endoscopy a- Cystoscopy in case of $. haematobium.
b- Colonoscopy and Sigmoidoscopy in case of $. mansoni.
Done in chronic cases to detect lesions and take biopsy.

32. Treatment
1- Praziquantel: It is the drug of choice. The dose is 40 mg/kg body weight, once, orally.
2- Merazide: This is a Commiphora plant extract, taken as two 300 mg capsules, one hour before breakfast, for 3 successive days.
3- Surgical treatment: Needed for irreversible lesions.

33. SCHISTOSOMA MANSONI Pathology and clinical picture
1- Stages of invasion and migration: same as in $. haematobium.
2- Stage of egg deposition = Acute stage = open lesion
Egg deposition in pelvic colon and rectum leading to erosion of mucosa and inflammation.

34. 3- Stage of tissue fibrosis = chronic stage = late stage.
 Egg trapped in wall leads to sandy patches, bilharzial nodules, polyps. These changes end by stricture, fistula, sinuses and rectal prolapsed.

35. - Liver leads to Symmer's fibrosis
50% of egg pass by blood to liver lead to granuloma formation around egg lead to hepatic periportal fibrosis that result in portal hypertension leads to open portosystemic anastomosis around cardiac end of the oesophagus leads to oesophageal varices.

37. - Lung
when portal pressure become more than systemic pressure, egg pass to blood to lungs leads to bilharzial corpulmonale.

38. Clinical picture
1- Stages of invasion and migration: The same as S. haematobioum.
2- Stage of acute intestinal phase: dysentery (passage of stool with mucus and blood), colic, fever, anorexia and loss of weight.

39. 3- Stage of chronic irreversible effects:
- Chronic intestinal form: Abdominal pain, diarrhea or even dysentery. Intestinal polyposis leads to severe bloody dysentery with protein and weight loss. Hypertrophic osteoarthropathy may occur.

40. - Hepatosplenic schistosomiasis
Early firm enlargement of liver with or without splenomegaly. Later on, portal hypertension, ascites, hematemesis and bleeding esophageal varices. Melena due to rupture of veins in rectum.

41. become distended up to 1–2 cm in diameter in association with portal hypertension.
Esophageal varices seven days after banding, showing ulceration at the site of banding

43. Diagnosis Laboratory diagnosis 1- Direct method: -
-Stool examination by direct smear method or by concentration method.
- Kato thick faecal smear: for egg counting to assess the intensity of infection
- Rrectal mucosa biobsy
-Rectal swab

44. 2- Indirect methods: As for. S. haematobium.
3- Blood examination: anaemia due to:
a. Blood loss results in iron deficiency anaemia.
b. Hypersplenism may result in pancytopenia.
c. Liver cell failure may results in prolonged prothrombin time with bleeding.

45. Treatment As for. S. haematobium. Oxammiquine (vancil) for $.m. only.
It is taken as mg/kg oral, in two doses per a day with 8 hours interval.

46. Prevention and Control of schistosomiasis
Schistosomiasis is a preventable disease but once complications occur, it is non-curative disease.
1- Health education (TV media)
Avoid urination or defecation in water canal.
Avoid washing or swimming in water canal.
Rapid drying of wet skin to prevent cercarial penetration.

47. 2- Personal prophylaxis
Wearing of boots and gloves.
Use of repellants.
Mass treatment.
a- Proper sanitation of the environment
- Clean water supply.
- Sanitary latrines.
- Proper sewage disposal.
- Construction of canals away from villages.
b- Treatment of canal to become safe by
- Addition of chlorine.
- Boiling of drinking water or
- Storage more than 48 hours.

48. 3- Snail control Physical method • Dryness of canals.
• Clearance of weeds to prevent feeding of snails.
• Wine screens at inlets of canals to collect snails.

49. Biological method • Toxic plants to snails. e.g. Balanites aegyptiaca.
• Natural enemies to snail as ducks, birds & other snails e.g.,Marisa spp.

50. Chemical methods
An ideal molluscicide should be cheap, easy to apply, effective in low concentration with residual effect and non-toxic to man, animals, fishes and plants.

51. • Bayluscide: 2 p.p.m. kills snails, their eggs, miracidia and cercariae.