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| Infection - Schistosomiasis | |
| by Mark Wright
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This disease was first described by Theodor Bilharz in 1851 and today affects 1:20 of the entire world's population. The main species that affect man are Scistosoma mansoni, S. haematobium and S. japonicum (also S. intercalatum, S. mattheei and S. mekongi). Each has a complex life cycle in which there is a sexual stage in humans and an asexual stage in snails. Miracadia (tiny ciliated forms of Schistosoma) udergo a series of asexual divisions to form a cyst, which bursts to form tiny sexual forms of the fluke called cercariae that live in water. Only 10 seconds of contact between the skin of a human and infected water allows the cercariae to penetrate the skin and enter the lymphatics where it causes irritation sometimes accompanied by a papular rash. Two weeks later the patient may develop symptoms of Katayama (fever, rigors, sweating, headache, urticaria, cough and facial oedema). This illness may last up to 3 months during which the flukes are migrating via the bloodstream to their final destination anywhere in the body - brain, eyes, bladder, bowel. After 12 weeks the eggs begin to appear in the urine. |
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| Life cycle of Scistosoma haematobium | |
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| Pathology | |
| The greatest egg burden is in the bladder. The body reacts to the worms and their eggs by forming a granuloma, mainly in the lamina propria and later in between the fibres of the detrusor. The eggs secrete a histiolytic antigen that evokes a cell mediated response attracting eosinophils. The inflammatory response leads to ischaemia and dead eggs provoke a foreign body giant cell reaction and calcification. Healing is followed by episodes of reinfection. Repeated episodes lead to CIS and carcinoma of the bladder. | |
| Investigations | |
| Eggs will be found in the urine, and usually they are the terminally spined S. haematobium. Cystoscopy will show minute yellow specks, the bilharzial tubercles. Later these granulomas enlarge and may form polyps which can calcify. IVU shows characteristic calcification in the bladder, ureters, seminal vesicles and vasa. | |
| Treatment | |
| Ideally, patients with suspected cases should be followed up until eggs appear in the urine or stools. However, the treatment is so simple and effective that it is often more practical to treat all suspected cases. A single dose of Praziquantel is given to the patient and may be repeated one month later. Local treatment of benign polyps and ulcers is by TUR. | |
| Complications | |
| Bladder Outflow Obstruction - contracture from healing of the bladder neck is often accompanied by a damaged detrusor. Calculi often form in the bladder and ureters which are typically dilated and calcified. | |
Bilharzial Carcinoma of the Bladder - 2 out of 3 are squamus cell carcinoma and the age incidence is young (mean 46 years). Dense fibrosis surrounds the bladder. Treatment by total radical cystectomy with or without reconstruction is effective (Ghonheim 1984). |
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Other - bulbar urethral stricture, prostatitis (the ova are distributed throughout the stroma), seminal vesicles are often chalked out by the calcified ova leading to haematospermia and painful ejaculation. Uterus, fallopian tubes and ovaries can all be affected (polypi of vulva can lead to dyspareunia and is often mistaken for Ca Vulva). |
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| Reference | |
| Ghonheim MA 1984 Tropical Urology and Renal Disease pp261-280 | |
| Feedback Any comments, ideas or answers? Email edu@bui.ac.uk |
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