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Genitourinary Schistosomiasis
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Q: Where is Schistosoma haematobium geographically distributed?
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A: Middle East, Egypt (Nile Valley), Africa, Europe, and India1.
2. Morphology of the Adult Worms
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Q: Describe the morphology of the male Schistosoma haematobium adult worm.
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A: Size is 10-15 mm X 1 mm1. It is flattened and folded to form the gynaecophoric canal2. The surface is covered by small tubercles except in the canal region2. It has a small sub-terminal oral sucker and a larger ventral sucker slightly behind the oral one2. There are 4-5 rounded, separate, smooth testes arranged in a line postero-lateral to the ventral sucker2. The male genital pore is just behind the ventral sucker2. The digestive system includes an oral opening surrounded by the oral sucker, an esophagus without a muscular pharynx that divides into 2 simple intestinal caeca in front of the ventral sucker2, and these caeca reunite at the middle of the body to form a single blind caecum3.
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Q: Describe the morphology of the female Schistosoma haematobium adult worm.
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A: Size is 20-25 X 0.25 mm3. It is cylindrical with a smooth surface3. Oral and ventral suckers are present but are weakly developed3. The oval ovary is located in the posterior 1/2 of the body, anterior to the intestinal reunion3. The uterus is long, contains up to 30 ova, and opens at the genital pore behind the ventral sucker3. Vitelline glands surround the single intestinal caecum from posterior to the ovary up to the posterior end4. The digestive system is similar to the male, but the reunion of the intestinal caeca is located at the junction of the anterior 2/3 with the posterior 1/3 of the body4.
3. Morphology of the Egg
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Q: Describe the morphology of the Schistosoma haematobium egg.
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A: It is 120 X 60 µ4, oval, non-operculated, transparent, and thin-shelled4. It is mature (contains miracidium) and has a terminal spine at the posterior end4.
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Q: What is the diagnostic stage for Schistosoma haematobium?
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A: The egg is the diagnostic stage4.
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Q: Where are Schistosoma haematobium eggs typically passed?
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A: In urine4.
4. Life Cycle
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Q: What is the habitat of adult Schistosoma haematobium worms in the human body?
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A: Vesical, pelvic, and prostatic plexuses of veins5.
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Q: What is the definitive host for Schistosoma haematobium?
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A: Man5.
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Q: What is the intermediate host for Schistosoma haematobium?
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A: Bulinus truncatus snail (in Egypt)5.
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Q: Is there a reservoir host for Schistosoma haematobium?
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A: No reservoir host5.
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Q: What is the infective stage of Schistosoma haematobium for humans?
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A: Furcocercous cercaria5.
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Q: How long does it take for the egg to hatch in fresh water?
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A: Within 20 minutes4.
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Q: What stage emerges from the egg in water?
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A: The miracidium4.
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Q: What happens after the miracidium penetrates the snail?
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A: It develops, through asexual multiplication, into 1st and 2nd generation sporocysts, which give rise to cercaria6.
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Q: Do schistosomes have a redial stage in the snail?
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A: No, there is no redial stage in schistosomes6.
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Q: How many cercariae can a single miracidium produce?
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A: Up to 100,000 cercariae6.
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Q: Describe the morphology of a Schistosoma haematobium cercaria.
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A: It is elongated, 500 µ in length, formed of a body (200 µ) and a forked (furcocercous) tail (300 µ)5....
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Q: How long can cercariae live in water?
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A: Only for 24-48 hours5.
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Q: What characteristic tropism do cercariae exhibit?
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A: They are photo- and thermo-tropic5.
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Q: What are the main methods of human infection by Schistosoma haematobium?
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A: Penetration of unbroken skin by cercaria5 and drinking of infected water, when the cercaria penetrates the mucous membrane before reaching the gastric acidity7.
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Q: How does the cercaria penetrate the skin?
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A: Within 15-20 minutes, with the help of secretions of penetration glands and the mechanical movement of the forked tail against the surface film of water droplets on the skin7.
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Q: Does skin penetration by cercaria occur under the water surface?
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A: No, penetration does not occur under the water surface7.
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Q: What does a cercaria become after penetrating the skin and losing its tail?
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A: Schistosomulum8.
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Q: Where does the schistosomulum travel after entering the bloodstream?
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A: It reaches the lungs within 48 hours8, then migrates via portal circulation to the liver8.
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Q: What happens in the liver?
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A: The schistosomulum grows and differentiates into sexually mature male and female adult worms within 7 weeks8.
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Q: Where do the adult worms migrate after maturing in the liver?
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A: The male carries the female in its gynaecophoric canal, and they move out of the liver, against the blood stream, to the small venules of the vesical, pelvic, and prostatic plexuses of veins8....
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Q: Where does the female adult worm primarily deposit eggs?
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A: In the small venules of the urinary bladder9.
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Q: How many eggs can a fertilized female deposit per day?
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A: Up to 500 eggs/day9.
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Q: How do the eggs pass through the venules and bladder mucosa?
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A: With the help of the piercing action of the terminal spine, pressure inside the venules, and proteolytic enzymes secreted by the embryo9.
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Q: How are the eggs released into the urine?
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A: When the bladder contracts, the eggs are released into the lumen with extra-vasated blood and are usually voided in the urine9.
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Q: What clinical sign is often associated with the passage of eggs in urine?
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A: Terminal hematuria9.
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Q: What stage is contained within the egg when it is passed in the urine?
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A: A fully developed miracidium10.
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Q: What is the pre-patent period for Schistosoma haematobium infection in humans?
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A: About 2-3 months10.
5. Pathogenicity and Clinical Manifestations
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Q: What stages of Schistosoma haematobium contribute to pathogenicity?
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A: Cercariae, adult worms, and eggs10.
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Q: Describe the pathogenicity related to cercariae (Stage of Invasion).
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A: It is called Cercarial Dermatitis10 or bather's itch11. It appears 2 hours after skin penetration10, characterized by papular pruritic rash and local oedema10.... This is a sensitization phenomenon11.
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Q: Describe the pathogenicity related to schistosomula or young adult worms (Migration Phase).
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A: This phase lasts 4-10 weeks12. It is characterized by toxic and allergic reactions from metabolic products of the maturing parasites13. Symptoms may include fever, headache, muscle pain, eosinophilia, urticaria, cough, wheezes, and leucocytosis11.... Pulmonary congestion with small patches of inflammation (Verminous pneumonitis) can occur, causing cough and hemoptysis11.... Hepatosplenomegaly may also be present13.
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Q: What is the main cause of pathogenicity in Schistosoma haematobium infection (Egg Deposition Phase)?
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A: The deposition of eggs in the different tissues12.
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Q: How do the miracidial antigens in the eggs affect the host's immune system?
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A: They stimulate both humoral and cell-mediated immune responses12.
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Q: Which immune response is primarily responsible for the pathological lesions?
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A: The cell-mediated immune response12.
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Q: What are the symptoms in the early acute stage of egg deposition?
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A: Tissue damage and hemorrhage from the passage of eggs, manifesting as terminal haematuria (blood in the last part of urination), increased frequency of micturition, and dysuria (burning pain during urination)14....
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Q: What happens in the late chronic stage (Tissue Proliferation, Repair, and Fibrosis)?
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A: Inflammatory reactions to eggs lead to fibrosis14.... This results in the formation of parasitic granulomas, sandy patches, nodules, papillomas, and ulcerations14. Degenerated or calcified eggs surrounded by fibrous and scar tissues cause obstructive changes17.
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Q: What are the components of a parasitic granuloma?
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A: Eggs at the center, surrounded by eosinophils, macrophages, and lymphocytes14.
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Q: Where are granulomas commonly found in genitourinary schistosomiasis?
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A: In the lower urinary tract, such as the urinary bladder and ureters14. The spermatic cord may also be involved14.
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Q: What are some urinary manifestations in chronic schistosomiasis?
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A: In the urinary bladder: polyps, ulcers, contracted bladder, calcified bladder, and malignancy (pre-cancerous)16. In the ureters: stricture and hydroureter (dilation)16. In the kidneys: hydronephrosis, secondary infection (pyonephrosis), and renal failure16. In the urethra: stricture16. In genital organs: pseudo-elephantiasis of the penis, and granuloma in the prostate, seminal vesicle, spermatic cord, ovaries, uterus, and vagina16.
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Q: What causes malignancy in the urinary bladder in chronic cases?
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A: Continuous toxic and mechanical irritation of infected bladder tissues by the eggs predisposes to malignancy16....
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Q: Describe the extra-urinary manifestation known as Bilharzial cor-Pulmonale.
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A: Eggs swept from the pelvic and vesical plexuses to the pulmonary artery branches produce granulomas and fibrosis19, leading to pulmonary hypertension18.... Pulmonary hypertension leads to right ventricular hypertrophy and right-sided heart failure18....
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Q: What causes ectopic lesions in chronic schistosomiasis?
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A: Fibrous and scar tissue block the migration of eggs, causing them to be swept back to other organs like the large intestine, lung, liver, brain, or spinal cord17.
6. Diagnosis
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Q: What clinical history is suggestive of Schistosoma haematobium infection?
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A: History of terminal haematuria and dysuria in an endemic area19. In mild infection, hematuria may occur after muscular activity19.
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Q: What is the primary direct laboratory method for diagnosis?
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A: Detection of eggs in urine by microscopic examination of the last drop of urine sample or after centrifugation19.
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Q: Can eggs be found in stool?
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A: Yes, in 5% of cases19.
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Q: What is the purpose of the hatching test?
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A: To differentiate between living and dead eggs20.
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Q: How do you identify a living egg using the hatching test?
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A: It is translucent, contains an intact moving miracidium, is surrounded by R.B.Cs., and hatches in fresh water (positive hatching test)20.
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Q: How do you identify a dead egg using the hatching test?
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A: It is opaque, contains a dead miracidium (not motile or silent), has no R.B.Cs, and does not hatch (negative hatching test)20.
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Q: What other direct laboratory methods are mentioned?
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A: ELISA for circulating antigens20, Cystoscopy (in chronic cases where eggs may not be detected in urine) for detection of histopathological lesions20, and PCR20.
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Q: What are the indirect laboratory methods for diagnosis?
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A: Serological tests for detection of antibodies, such as Indirect Haemagglutination test (IHA), Indirect Fluorescent Antibody test (IFA), and Enzyme-Linked Immunosorbent Assay (ELISA)21.
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Q: When are PCR and immunodiagnosis used?
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A: In cases of a suspected infection without proof of eggs21.
7. Treatment
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Q: What is the only drug available for the treatment of Schistosoma haematobium?
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A: Praziquantel21.
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Q: What is the typical dose of Praziquantel?
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A: 40 mg/kg body weight21.
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Q: Does Praziquantel affect the ova?
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A: No, Praziquantel does not affect ova21.
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Q: What should be done after treatment with Praziquantel?
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A: Repeat the microscopic examination of urine for ova 4–6 weeks after treatment21.
8. Prevention and Control
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Q: What are the basic principles for prevention and control?
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A: Protection (prophylaxis from infection), treatment of cases, and snail control22.
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Q: What are some methods for personal protection (prophylaxis)?
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A: Health education to prevent urination in or near water streams22, wearing of boots and gloves22, use of repellents e.g., dimethyl phthalate22, quick and thorough drying of exposed wet skin22, ensuring pure water supply and sanitary disposal of excreta22.
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Q: How can treatment of cases contribute to prevention and control?
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A: Through mass treatment by Praziquantel22.
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Q: What are the physical methods for snail control?
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A: Dryness of canals, periodic clearance of canals from vegetations, and wire screens at inlets of canals to collect snails22.
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Q: What are the biological methods for snail control?
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A: Using natural enemies of snails e.g., birds, and certain toxic plants e.g., Balanites aegyptiaca23.
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Q: What are the chemical methods for snail control?
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A: Using molluscicides (chemical substances to kill snails) such as Copper sulphate, Sodium pentachlorophenate, and Baylucide23.
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