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| {{Infobox_Disease |
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| Name = {{PAGENAME}} |
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| Image = Schistosomiasis_itch.jpeg |
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| Caption = Skin vesicles created by the penetration of Schistosoma. Source: CDC |
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| DiseasesDB = |
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| ICD10 = {{ICD10|B|65||b|65}} |
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| ICD9 = {{ICD9|120}} |
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| ICDO = |
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| OMIM = |
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| MedlinePlus = |
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| MeshID = D012552 |
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| }}
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| {{Schistosomiasis}} | | {{Schistosomiasis}} |
| {{CMG}} | | {{CMG}}; {{AE}} {{ADG}} {{JH}}. |
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| | '''For patient information, click [[Schistosomiasis (patient information)|here]]''' |
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| ==Types== | | {{SK}} Bilharzia; Bilharziasis, Bilharziosis; Katayama fever, Blood fluke infection |
| There are five species of flatworms that cause schistosomiasis. Each causes a different clinical presentation of the [[disease]]. Schistosomiasis may localize in different parts of the body, and its localization determines its particular clinical profile.
| | ==[[Schistosomiasis overview|Overview]]== |
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| * ''[[Schistosoma mansoni]]'' ([[ICD|ICD-10]] B65.1) and ''[[Schistosoma intercalatum]]'' (B65.8) cause [[intestinal]] schistosomiasis
| | ==[[Schistosomiasis historical perspective|Historical Perspective]]== |
| * ''[[Schistosoma haematobium]]'' (B65.0) causes [[urine|urinary]] schistosomiasis
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| * ''[[Schistosoma japonicum]]'' (B65.2) and ''[[Schistosoma mekongi]]'' (B65.8) cause Asian intestinal schistosomiasis
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| ==Geographical distribution and epidemiology== | | ==[[Schistosomiasis classification|Classification]]== |
| The disease is found in tropical countries in Africa, Caribbean, eastern South America, east Asia and in the Middle East. ''[[Schistosoma mansoni]]'' is found in parts of South America and the Caribbean, Africa, and the Middle East; ''S. haematobium'' in Africa and the Middle East; and ''S. japonicum'' in the Far East. ''S. mekongi'' and ''S. intercalatum'' are found focally in Southeast Asia and central West Africa, respectively.
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| An estimated 207 million people have the disease, 120 million symptomatic. A few countries have eradicated the disease, and many more are working towards it. The [[World Health Organization]] is promoting efforts working towards this goal. In some cases, urbanization, pollution, and/or consequent destruction of snail habitat has reduced exposure, with a subsequent decrease in new infections. The most common way of getting schistosomiasis in developing countries is by wading or swimming in lakes, ponds and other bodies of water which are infested with the snails (usually of the ''[[Biomphalaria]]'', ''[[Bulinus]]'', or ''Oncomelania'' genus) that are the [[natural reservoir]]s of the ''Schistosoma'' pathogen.
| | ==[[Schistosomiasis pathophysiology|Pathophysiology]]== |
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| ==Life cycle== | | ==[[Schistosomiasis causes|Causes]]== |
| [[Image:Schistosomiasis Life Cycle.jpeg|left|thumb|350px|Schistosomiasis life cycle. Source: CDC]] | |
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| Schistosomes have a typical trematode vertebrate-invertebrate lifecycle, with humans being the definitive host. The life cycles of all five human schistosomes are broadly similar: parasite eggs are released into the environment from infected individuals, hatching on contact with fresh water to release the free-swimming [[miracidium]]. Miracidia infect fresh-water snails by penetrating the snail's foot. After infection, close to the site of penetration, the miracidium transforms into a primary (mother) sporocyst. Germ cells within the primary sporocyst will then begin dividing to produce secondary (daughter) sporocysts, which migrate to the snail's hepatopancreas. Once at the hepatopancreas, germ cells within the secondary sporocyst begin to divide again, this time producing thousands of new parasites, known as cercariae, which are the larvae capable of infecting mammals.
| | ==[[Schistosomiasis differential diagnosis|Differentiating Schistosomiasis from other Diseases]]== |
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| Cercariae emerge daily from the snail host in a [[circadian]] rhythm, dependent on ambient temperature and light. Young cercariae are highly motile, alternating between vigorous upward movement and sinking to maintain their position in the water. Cercarial activity is particularly stimulated by water turbulence, by shadows and by chemicals found on human skin. Penetration of the human skin occurs after the cercaria have attached to and explored the skin. The parasite secretes enzymes that break down the skin's protein to enable penetration of the cercarial head through the skin. As the cercaria penetrates the skin it transforms into a migrating schistosomulum stage.
| | ==[[Schistosomiasis epidemiology and demographics|Epidemiology and Demographics]]== |
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| The newly transformed schistosomulum may remain in the skin for 2 days before locating a post-capillary [[venule]]; from here the schistosomulum travels to the lungs where it undergoes further developmental changes necessary for subsequent migration to the liver. Eight to ten days after penetration of the skin, the parasite migrates to the [[liver sinusoid]]s. ''S. japonicum'' migrates more quickly than S. mansoni, and usually reaches the liver within 8 days of penetration. Juvenile ''S. mansoni'' and ''S. japonicum'' worms develop an oral sucker after arriving at the liver, and it is during this period that the parasite begins to feed on red blood cells. The nearly-mature worms pair, with the longer female worm residing in the gynaecophoric channel of the male. Adult worms are about 10 mm long. Worm pairs of S. mansoni and S. japonicum relocate to the [[mesenteric]] or rectal veins. ''S. haematobium'' schistosomula ultimately migrate from the liver to the perivesical venous plexus of the bladder, ureters, and kidneys through the hemorrhoidal plexus.
| | ==[[Schistosomiasis risk factors|Risk Factors]]== |
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| Parasites reach maturity in six to eight weeks, at which time they begin to produce eggs. Adult ''S. mansoni'' pairs residing in the mesenteric vessels may produce up to 300 eggs per day during their reproductive lives. ''S. japonicum'' may produce up to 3000 eggs per day. Many of the eggs pass through the walls of the blood vessels, and through the intestinal wall, to be passed out of the body in faeces. ''S. haematobium'' eggs pass through the ureteral or bladder wall and into the urine. Only mature eggs are capable of crossing into the digestive tract, possibly through the release of [[proteolytic]] enzymes, but also as a function of host immune response, which fosters local tissue ulceration. Up to half the eggs released by the worm pairs become trapped in the mesenteric veins, or will be washed back into the liver, where they will become lodged. Worm pairs can live in the body for an average of four and a half years, but may persist up to 20 years.
| | ==[[Schistosomiasis natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| Trapped eggs mature normally, secreting [[antigens]] that elicit a vigorous [[immune]] response. The eggs themselves do not damage the body. Rather it is the cellular infiltration resultant from the immune response that causes the pathology classically associated with schistosomiasis.
| | ==Diagnosis== |
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| ==Pathology==
| | [[Schistosomiasis history and symptoms|History and Symptoms]] | [[Schistosomiasis physical examination|Physical Examination]] | [[Schistosomiasis laboratory findings|Laboratory Findings]] | [[Schistosomiasis other imaging findings|Imaging Findings]] | [[Schistosomiasis other diagnostic studies|Other Diagnostic Studies]] |
| Above all, schistosomiasis is a [[chronic disease]]. Pathology of ''S. mansoni'' and ''S. japonicum'' schistosomiasis includes: [[Katayama fever]], hepatic perisinusoidal egg [[granulomas]], Symmers’ pipe stem periportal fibrosis, [[portal hypertension]], and occasional [[embolism|embolic]] egg granulomas in [[brain]] or [[spinal cord]]. Pathology of ''S. haematobium'' schistosomiasis includes: [[hematuria]], [[scar]]ring, [[calcification]], [[squamous cell carcinoma]], and occasional embolic egg granulomas in brain or spinal cord. [[Bladder Cancer]] diagnosis and mortality are generally elevated in affected areas.
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| ==Clinical features==
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| Many infections are subclinically symptomatic, with mild anemia and malnutrition being common in endemic areas. Acute schistosomiasis (Katayama's fever) may occur weeks after the initial infection, especially by ''S. mansoni'' and ''S. japonicum''. Manifestations include:
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| * [[Abdominal pain]]
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| * [[Cough]]
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| * [[Diarrhea]]
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| * [[Eosinophilia]] - extremely high [[eosinophil granulocyte]] count.
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| * [[Fever]]
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| * [[Fatigue (physical)|Fatigue]]
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| * [[Hepatosplenomegaly]] - the enlargement of both the [[liver]] and the [[spleen]].
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| Occasionally [[central nervous system]] lesions occur: cerebral granulomatous disease may be caused by ectopic ''S. japonicum'' eggs in the [[brain]], and granulomatous lesions around ectopic eggs in the [[spinal cord]] from ''S. mansoni'' and ''S. haematobium'' infections may result in a transverse [[myelitis]] with flaccid [[paraplegia]]. Continuing infection may cause granulomatous reactions and [[fibrosis]] in the affected organs, which may result in manifestations that include:
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| * Colonic [[polyposis]] with bloody diarrhea (''Schistosoma mansoni'' mostly);
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| * [[Portal hypertension]] with [[hematemesis]] and [[splenomegaly]] (''S. mansoni'', ''S. japonicum'');
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| * [[Cystitis]] and ureteritis (''S. haematobium'') with [[hematuria]], which can progress to [[bladder cancer]];
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| * [[Pulmonary hypertension]] (''S. mansoni'', ''S. japonicum'', more rarely ''S. haematobium'');
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| * [[Glomerulonephritis]]; and central nervous system lesions.
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| ==Laboratory diagnosis==
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| Microscopic identification of eggs in [[feces|stool]] or [[urine]] is the most practical method for diagnosis. The stool exam is the more common of the two. For the measurement of eggs in the feces of presenting patients the scientific unit used is [[epg]] or [[eggs per gram]]. Stool examination should be performed when infection with ''S. mansoni'' or ''S. japonicum'' is suspected, and urine examination should be performed if ''S. haematobium'' is suspected.
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| Eggs can be present in the stool in infections with all ''Schistosoma'' species. The examination can be performed on a simple smear (1 to 2 mg of fecal material). Since eggs may be passed intermittently or in small amounts, their detection will be enhanced by repeated examinations and/or concentration procedures (such as the formalin-ethyl acetate technique). In addition, for field surveys and investigational purposes, the egg output can be quantified by using the [[Kato-Katz technique]] (20 to 50 mg of fecal material) or the Ritchie technique.
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| Eggs can be found in the urine in infections with (recommended time for collection: between noon and 3 PM) S. japonicum' and with S. intercalatum. Detection will be enhanced by [[centrifugation]] and examination of the sediment. Quantification is possible by using filtration through a [[nucleopore]] membrane of a standard volume of urine followed by egg counts on the membrane. Investigation of ''S. haematobium'' should also include a pelvic x-ray as bladder wall calcificaition is highly characteristic of chronic infection.
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| Recently a field evaluation of a novel handheld microscope was undertaken in Uganda for the diagnosis of intestinal schistosomiasis by a team led by Dr. Russell Stothard who heads the Schistosomiasis Control Iniative at the Natural History Museum, London. His report abstract may be found here: [http://looksmall.com/news.asp]
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| [[Image:Schistosoma bladder histopathology.jpeg|thumb|left|Photomicrography of bladder in ''S. hematobium'' infection, showing clusters of the parasite eggs with intense eosinophilia, Source: CDC]]
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| Tissue [[biopsy]] (rectal biopsy for all species and biopsy of the bladder for ''S. haematobium'') may demonstrate eggs when stool or urine examinations are negative.
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| The eggs of ''S. haematobium'' are ellipsoidal with a terminal spine, ''S. mansoni'' eggs are also ellipsoidal but with a lateral spine, ''S. japonicum'' eggs are spheroidal with a small knob.
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| [[Antibody]] detection can be useful in both clinical management and for [[epidemiologic]] surveys.
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| ==Treatment== | | ==Treatment== |
| Schistosomiasis is readily treated using a single oral dose of the drug [[Praziquantel]]. While Praziquantel is safe and highly effective in curing an infected patient, it does not prevent re-infection by cercariae and is thus not an optimum treatment for people living in endemic areas. As with other major parasitic diseases, there is ongoing and extensive research into developing a vaccine that will prevent the parasite from completing its life cycle in humans.
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| [[Antimony]] has been used in the past to treat the disease. In low doses, this [[toxic]] metalloid bonds to [[sulfur]] atoms in [[enzymes]] used by the parasite and kills it without harming the host. This treatment is not referred to in present-day peer-review scholarship; [[Praziquantel]] is universally used. Outside of the US, there is a second drug available for treating ''Schistosoma mansoni'' (exclusively) called [[Oxamniquine]].
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| Mirazid, a new Egyptian drug, is under investigation for oral treatment of the disease.
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| Experiments have shown medicinal [[Castor oil]] as an oral anti-penetration agent to prevent Schistosomiasis and that praziquantel's effectiveness depended upon the vehicle used to administer the drug (e.g., Cremophor / Castor oil).<ref>{{cite web | title=Schistosoma mansoni: experimental chemoprophylaxis in mice using oral anti-penetration agents. | url=http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=2507345&query_hl=1itool=pubmed_docsum | format=| publisher=pubmed | accessdate=2007-01-25}}</ref>
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| Additionally Dr Chidzere of Zimbabwe researched the Gopo Berry (''Phytolacca dodecandra'') during the 1980's and found that the Gopo Berry could be used in the control of the freshwater snails which carry the bilharzia disease (Schistosomiasis parasite). Dr Chidzere in his interview to Andrew Blake (1989) reported concerns of muti-national chemical companies keen to rubbish the Gopu Berry alternative for snail control <ref> The Gopu Berry p33. Part 4 School Journal number.2 1989 Dept of Education Wellington N.Z </ref>. Reputedly Gopo Berries from hotter Ethiopia climates yield the best results. Later studies were between 1993-95 by the Danish Research Network for international health. <ref> http://enrecahealth.ku.dk/postgrad_dbl_en/chihaka_abs/ </ref>
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| ==Prevention through good design==
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| The main focus of prevention is eliminating the water-borne snails which are [[natural reservoir]]s for the disease. This is usually done by identifying bodies of water, such as lakes, ponds, etc., which are infested, forbidding or warning against swimming and adding niclosamide, [[acrolein]], [[copper sulfate]], etc., to the water in order to kill the snails.
| | [[Schistosomiasis medical therapy|Medical Therapy]] | [[Schistosomiasis prevention|Prevention]] | [[Schistosomiasis cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Schistosomiasis future or investigational therapies|Future or Investigational Therapies]] |
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| Unfortunately for many years from the 1950s onwards, despite the efforts of some clinicians to get civil engineers to take it into account in their designs, civil engineeers built vast dam and irrigation schemes, oblivious of the fact that they would cause a massive rise in water-borne infections from schistosomiasis, even though with a little care the schemes could have been designed to minimise such effects, the detailed specifications having been laid out in various UN documents since the 1950s. Irrigation schemes can be designed to make it hard for the snails to colonise the water, and to reduce the contact with the local population.
| | ==Case Studies== |
| <ref>Charnock, Anne (1980) Taking Bilharziasis out of the irrigation equation. New Civil Engineer, 7 August. 1980 Bilharzia caused by poor civil engineering design due to ignorance of cause and prevention</ref>
| | [[Schistosomiasis case study one|Case #1]] |
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| Failure for engineers to take this into account is an interesting example of the Relevance Paradox and is a good example of the failure of formal education and information systems to transmit tacit knowledge.
| | == Related Chapters== |
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| ==Prevention and hygiene== | |
| Prevention is best accomplished by eliminating the water-dwelling snails which are the [[natural reservoir]] of the disease. [[Acrolein]], [[copper sulfate]], and niclosamide can be used for this purpose. Recent studies have suggested that snail populations can be controlled by the introduction or augmentation of existing crayfish populations; as with all ecological interventions, however, this technique must be approached with caution.
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| Individuals can guard against schistosomiasis infection by avoiding bodies of water known or likely to harbor the carrier snails.
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| In 1989, Aklilu Lemma and Legesse Wolde-Yohannes received the Right Livelihood Award for their research on the sapindus-Plant (''Phytolacca dodecandra''), as a preventative measure for the disease.
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| == Histopathology: Rectum, Schistosomiasis==
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| {{#ev:youtube|9VpqxnPRvL8}}
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| == See also ==
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| * [[Tropical disease]] | | * [[Tropical disease]] |
| | * [[Schistosoma]] |
| | * [[Swimmer's itch]] |
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| ==References==
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| <references/>
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| * [[Center for Disease Control]], ''[http://www.dpd.cdc.gov/dpdx/HTML/Schistosomiasis.htm Schistosomiasis]''. (2004)
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| ==External links==
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| * [http://www.who.int/wormcontrol/en/ World Health Organization Partners for Parasite Control website]
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| * [http://www.who.int/wormcontrol/documents/fact_sheets/schistosomiasis/en/ World Health Organization fact sheet on the disease]
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| * [http://www.wellcome.ac.uk/en/labnotes5/animation_popups/schisto.html Wellcome animation of the life cycle of the parasite]
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| * [http://www.schisto.org Schistosomiasis Control Initiative]
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| * [http://www.eu-contrast.eu CONTRAST, a research project on optimized schistosomiasis control in Sub-saharan Africa]
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| * [http://www.who.int/tdr/ World Health Organization Tropical Disease Research programme]
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| * [http://www.path.cam.ac.uk/~schisto Cambridge University Schistosomiasis Research Group]
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| * [http://www.york.ac.uk/res/schisto/ York University Schistosomiasis Research Group]
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| * [http://www.cartercenter.org/healthprograms/program4.htm Schistosomiasis (Bilharzia) Control and Prevention: The Carter Center Schistosomiasis Control Program]
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| * [http://www.lib.uiowa.edu/hardin/md/schistosomiasis.html Links to Schistosomiasis pictures (Hardin MD/Univ of Iowa)]
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| * [http://bioinfo.cpqrr.fiocruz.br FIOCRUZ - Schistomiasis Research Group]
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| * [http://www.ucsf.edu/mckerrow/slide.html Sandler Center for Basic Research in Parasitic Diseases, University of California San Francisco]
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| * [http://www.neighbourhoodnews.com.au/default.asp?sourceid=&smenu=1&twindow=&mad=&sdetail=3948&wpage=1&skeyword=&sidate=&ccat=&ccatm=&restate=&restatus=&reoption=&retype=&repmin=&repmax=&rebed=&rebath=&subname=&pform=&sc=1175&hn=neighbourhoodnews&he=.com.au Vacine developed in Queensland, Australia]
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| *[http://www.dblnet.dk DBL - Centre for Health Research and Development]
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| *10. Charnock, Anne (1980) Taking Bilharziasis out of the irrigation equation. New Civil Engineer, 7 August. Bilharzia caused by poor civil engineering design due to ignorance of cause and prevention.
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| <!-- [[Category:Diving medicine]] No connection with diving made in the article! -->
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| [[Category:Neglected diseases]] | | [[Category:Neglected diseases]] |
| [[Category:Infectious disease]]
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