Schistosomiasis, also known as bilharziasis or snail fever, is a primarily tropical parasitic disease caused by the larvae of one or more of five types of flatworms or blood flukes known as schistosomes. The name bilharziasis comes from Theodor Bilharz, a German pathologist, who identified the worms in 1851. Schistosoma haematobium Schistosoma mansoni Schistosoma intercalatum Schistosoma japonicum/Schistosoma mekongi Africa: most of the countries of North Africa; widespread in Central and West Africa; in eastern Africa present from Somalia to the Cape and on the islands offshore, including Madagascar and Mauritius. Middle East: present in most countries. There might also be small foci in India around Bombay and in Madras State. A total of about 90 million people are infected worldwide. Africa: North Africa (Morocco, Tunisia, Egypt, southern Sudan); East Africa (from Ethiopia down to South Africa and Madagascar); most countries of Central and West Africa. Middle East (Lebanon, Oman, Saudi Arabia, Somalia, Yemen). Americas: in South America and some of the Caribbean islands. There are limited foci in : Central Africa including Cameroon, Congo, Congo Democratic Republic (Zaire), Equatorial Guinea, Gabon, and possibly in Central African Republic, Chad, Mali and Nigeria. China, Indonesia. Philippines. Thailand. The male measures 1020 mm _ 0.9 mm and the cuticle has fine tuberculations. There are 45 testes. The female has a long uterus, with the ovary in the posterior third of the body. There are 10100 eggs in the uterus at one time. The adults are smaller than those of the other species. The male measures 613 mm _ 0.751.0 mm and the cuticle has coarse tuberculations. There are 413 (usually 69) testes. The ovary of the female is situated anteriorly. There is usually only 1 egg in the uterus at one time. The male measures 1220 mm _ 0.50.55 mm and has no cuticular tuberculations. There are 67 testes. The female has the ovary at about the middle of the body. There are 5200 eggs in the uterus at one time. The male measures 1114 mm _ 0.30.4 mm. There are 27 testes. The female has 560 eggs in the uterus at one time. Ciliated miracidium. Note anterior penetration glands. Dark field. Actual size 80 m.Adults of Schistosoma sp. in lung tissue, stained with H&EHigher magnification of one of the worms, showing the tuberculate exterior of the adult wormUrinaryS. hematobiumIntestinalS. mansoniS. japonicum S. intercalatumS. mekongi A cercarial dermatitis (swimmers itch) may appear 24 h after first infection but seldom lasts more than 48 h. There are usually no symptoms until 510 weeks after infection, when there may be mild allergic manifestations in visitors but these are rare in indigenous populations. Maximum egg production begins 1012 weeks after infection. Haematuria (found in about 50% of cases), dysuria and increased frequency of micturition are typical clinical signs and may persist intermittently for years. hydroureter, hydronephrosis and uraemia.Schistosoma near urethraInner surface of the bladder showing nests of calcified ova (sandy patches) (arrowed) of S. hematobium.Intravenous pyelogram of a woman infected with S. haematobium showing bilateral hydronephrosiswith deformity of both ureters.Section of bladder. Eggs of S. haematobium (many are calcified or black eggs) can be seenwith epithelial squamous cell metaplasia (arrowed).S. japonicum.S. mekongi.S. mansoni.S. intercalatum As for S. haematobium.Allergic manifestationsKatayama syndrome serum sickness portal hypertension with splenomegaly oesophagial varices hypersplenism ascitis pulmonary hypertension CNS lesions: spine - transverse myelitis cerebral seizures (S. japonicum) intestinal polyposis: both sessile and pedunculated chronic salmonellosis intestinal granulomatosis: contractures of colon, intusseceptionEgg granuloma of S. mansoni in liver with surrounding epitheloid cells and some leucocyticinfiltrationGranuloma in the liver due to Schistosoma mansoni.The S mansoni egg is at the center of the granuloma.Two boys with advanced schistosomiasis mansoni. Note collateral venous circulation in nearestpatient. The presence of eggs in the faeces or urine is still the most widely used method of diagnosis. Schistosoma mansoni eggs are large (114 to 180 m long by 45-70 m wide) and have a characteristic shape, with a prominent lateral spine near the posterior end. The anterior end is tapered and slightly curved. When the eggs are excreted in stool, they contain a mature miracidium. The eggs of Schistosoma haematobiumare large (110-170 m long by 40-70 m wide) and bear a conspicuous terminal spine. Eggs contain a mature miracidium when shed in urine. The eggs of Schistosoma japonicumare large and more rounded than other species, measuring 70-100 m long by 55-64 m wide. The spine on S. japonicumeggs is smaller and less conspicuous than other species. Eggs are shed in stool. Schistosoma intercalatumis related to S. haematobium, but restricted to east-central Africa. The eggs are similar to S. haematobium in general shape and in possessing a terminal spine, but are usually longer (140-240 m), often have an equatorial (central) bulge and are shed in stool, not urine. Sedimentation Ceroscopy Rectal biopsy hematuria (terminal) urinary frequency pyuria pyelonephritis obstructive uropathy cancer of bladder (squamous cell) distant metastases (spinal column) (pulmonary hypertension) History of freshwater exposure portal hypertension with splenomegaly oesophagial varices hypersplenism ascitis pulmonary hypertension CNS lesions: spine - transverse myelitis cerebral seizures (S. japonicum) ELISA & immunoblotting techniques are the most convenient. A dipstick ELISA for urine samples, using an SEA can effectively diagnose schistosomiasis and correlates well with quantitative egg counts. Circulating cathodic antigen (CCA) Chemotherapy SurgeryPraziquantel MetrifonateAtropine sulphateOxamniquine Intrinsic Factors (deal with man) Extrinsic factors (snail control): Mechanical control Biological control Chemical control (molluscicides)