What is schistosomiasis?

Schistosomiasis (bilharzia) is a parasitic disease caused by blood flukes of the genus Schistosoma — the second most devastating parasitic infection after malaria. Humans are infected by swimming or wading in freshwater containing cercariae (infectious larvae) released by aquatic snails. The worms mature in the bloodstream and lay eggs that trigger inflammatory reactions — causing liver fibrosis, bladder disease, anaemia, malnutrition and bladder cancer in chronic infection.

How is schistosomiasis transmitted?

The lifecycle: infected humans excrete schistosome eggs in urine (S. haematobium) or faeces (S. mansoni, S. japonicum) into freshwater. Eggs hatch and infect specific freshwater snails (intermediate hosts). Snails release cercariae into water. Humans are infected through skin contact with cercariae during swimming, bathing, washing, irrigating or wading. Person-to-person transmission does NOT occur — the snail intermediate host is essential.

What diseases does schistosomiasis cause?

Urogenital schistosomiasis (S. haematobium): haematuria (blood in urine — the hallmark); bladder inflammation and fibrosis; bladder cancer (squamous cell carcinoma); hydronephrosis; female genital schistosomiasis (FGS); male genital schistosomiasis affecting sperm function. Intestinal/hepatosplenic schistosomiasis (S. mansoni, S. japonicum): diarrhoea; hepatic periportal fibrosis (Symmers fibrosis); portal hypertension; oesophageal varices; splenomegaly; and in children — stunting, anaemia and cognitive impairment.

What is female genital schistosomiasis?

FGS occurs when S. haematobium eggs are deposited in the female genital tract — the cervix, vagina, vulva, fallopian tubes or uterus — causing mucosal lesions visible on colposcopy ("sandy patches"), contact bleeding, discharge, pelvic pain and infertility. FGS affects up to 40 million women and girls in endemic areas. It increases HIV susceptibility approximately 3-fold (by disrupting the cervical epithelial barrier). It is rarely diagnosed because clinicians in endemic areas do not look for it.

Is there a vaccine for schistosomiasis?

No approved vaccine exists. Several candidates are in clinical development — most advanced is Sm-p80 (targeting S. mansoni p80 antigen) in Phase 2 trials. A schistosomiasis vaccine would be transformative for endemic communities. The Bill & Melinda Gates Foundation and WHO NTD programme are the primary funders.

How is schistosomiasis treated?

Praziquantel — a single oral dose of 40mg/kg — is the only available treatment. It kills adult schistosome worms but not eggs or cercariae, so reinfection in endemic settings is common. Praziquantel is safe (in adults and children over 4 years), inexpensive (donated supply <$0.20/dose) and on the WHO Essential Medicines List. It does not reverse established organ fibrosis — early treatment before damage accrues is therefore critical.

What is mass drug administration for schistosomiasis?

WHO targets school-aged children in endemic areas for annual or twice-annual praziquantel MDA — regardless of individual diagnosis. Children aged 5-14 are targeted because they have the highest worm burdens (from playing in freshwater). MDA prevents morbidity accumulation, reduces anaemia, improves nutritional status and cognitive development, and reduces transmission. Since 2002, Merck KGaA has donated over 250 million praziquantel tablets through WHO for MDA programmes.

What is the link between schistosomiasis and bladder cancer?

Chronic S. haematobium infection causes squamous cell carcinoma of the bladder — classified as a Group 1 carcinogen by IARC. The mechanism: egg-induced chronic inflammation → epithelial metaplasia → carcinoma. S. haematobium bladder cancer presents at a younger age (30s-40s) and with worse prognosis than transitional cell carcinoma. In endemic Africa, up to 30% of bladder cancers are attributable to schistosomiasis.

Why does schistosomiasis persist despite available treatment?

Multiple barriers perpetuate schistosomiasis: freshwater contact is unavoidable for communities dependent on lakes, rivers and irrigation for livelihood and sanitation; praziquantel treats infection but does not prevent immediate reinfection; MDA coverage is incomplete and not sustained; snail control (mollusciciding) is expensive and complex; there is no vaccine; and WASH improvements — the permanent solution — require infrastructure investment far beyond health budgets.

How does GMJ News cover schistosomiasis?

GMJ News covers WHO schistosomiasis MDA data, FGS awareness, bladder cancer link, praziquantel access and vaccine development. Schistosomiasis is part of the GMJ's NTD coverage — the principles of preventive chemotherapy, MDA and snail control inform broader tropical medicine coverage relevant to PHIG's global health agenda.

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Schistosomiasis

Q: What is mass drug administration for schistosomiasis?

WHO targets school-aged children in endemic areas for annual or twice-annual praziquantel MDA — regardless of individual diagnosis. Children aged 5-14 are targeted because they have the highest worm burdens (from playing in freshwater). MDA prevents morbidity accumulation, reduces anaemia, improves nutritional status and cognitive development, and reduces transmission. Since 2002, Merck KGaA has donated over 250 million praziquantel tablets through WHO for MDA programmes.

Q: What is the link between schistosomiasis and bladder cancer?

Chronic S. haematobium infection causes squamous cell carcinoma of the bladder — classified as a Group 1 carcinogen by IARC. The mechanism: egg-induced chronic inflammation → epithelial metaplasia → carcinoma. S. haematobium bladder cancer presents at a younger age (30s-40s) and with worse prognosis than transitional cell carcinoma. In endemic Africa, up to 30% of bladder cancers are attributable to schistosomiasis.

Q: Why does schistosomiasis persist despite available treatment?

Multiple barriers perpetuate schistosomiasis: freshwater contact is unavoidable for communities dependent on lakes, rivers and irrigation for livelihood and sanitation; praziquantel treats infection but does not prevent immediate reinfection; MDA coverage is incomplete and not sustained; snail control (mollusciciding) is expensive and complex; there is no vaccine; and WASH improvements — the permanent solution — require infrastructure investment far beyond health budgets.

Q: How does GMJ News cover schistosomiasis?

GMJ News covers WHO schistosomiasis MDA data, FGS awareness, bladder cancer link, praziquantel access and vaccine development. Schistosomiasis is part of the GMJ's NTD coverage — the principles of preventive chemotherapy, MDA and snail control inform broader tropical medicine coverage relevant to PHIG's global health agenda.

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

Summary Statistics Glossary GMJ news FAQ Documents Organizations Research

Schistosomiasis (bilharzia) — caused by parasitic blood flukes (Schistosoma species) transmitted through contact with contaminated freshwater — is the second most devastating parasitic disease after malaria, infecting approximately 240 million people and causing an estimated 200,000 deaths per year in 78 endemic countries across Africa, Latin America and Asia (WHO). Most disease burden comes from chronic infection causing liver fibrosis, portal hypertension, bladder cancer (Schistosoma haematobium), anaemia and malnutrition. Praziquantel — an inexpensive, safe drug — is the treatment of choice; mass drug administration (MDA) programmes are the primary control strategy.

Key messages

240 million infected

Schistosomiasis (bilharzia) infects approximately 240 million people — the second most devastating parasitic disease globally after malaria — causing an estimated 200,000 deaths and 1.9 million disability-adjusted life years per year (WHO).

Freshwater transmission

Schistosomiasis is transmitted through contact with freshwater contaminated with cercariae — infectious larvae released by aquatic snails. Swimming, bathing, washing or wading in infected water allows larvae to penetrate through the skin.

Two main syndromes

Urogenital schistosomiasis (S. haematobium — Africa, Middle East): haematuria, bladder fibrosis, bladder cancer, female genital schistosomiasis (FGS), male infertility. Intestinal schistosomiasis (S. mansoni, S. japonicum): liver fibrosis, portal hypertension, hepatosplenomegaly.

Praziquantel — the essential medicine

Praziquantel — a single oral dose — effectively kills adult schistosome worms and is the only available treatment. It is on the WHO Essential Medicines List, cheap (<$0.20/treatment with donated supply), and forms the basis of mass drug administration.

MDA — WHO strategy

WHO targets regular preventive chemotherapy (praziquantel) through school-based mass drug administration (MDA) for all school-aged children in endemic areas, regardless of individual diagnosis.

Female genital schistosomiasis

Female genital schistosomiasis (FGS) — poorly recognised and underdiagnosed — affects up to 40 million women, causing genital lesions, pain, abnormal bleeding, infertility and a 3-fold increased HIV susceptibility. It is one of the most neglected consequences of schistosomiasis.

Key statistics

240M

people infected globally

WHO

200K

estimated deaths/year

WHO

endemic countries

WHO

93%

of cases in Sub-Saharan Africa

WHO

40M

women with female genital schistosomiasis

WHO/research

increased HIV risk from FGS

WHO/research

Schistosomiasis cases requiring treatment by region — WHO 2023

Source: WHO preventive chemotherapy data. Sub-Saharan Africa dominates global burden.

Glossary of key terms

Schistosoma species
WHOFive main species cause human schistosomiasis: S. haematobium (urogenital — Africa/Middle East); S. mansoni (intestinal — Africa, Americas); S. japonicum (intestinal — East Asia); S. mekongi (Mekong region); S. intercalatum (Central Africa).

Cercariae
WHOFree-swimming infectious larvae released from freshwater snails (Biomphalaria sp. for intestinal; Bulinus sp. for urogenital) — that penetrate intact human skin during water contact, initiating schistosomiasis infection.

Praziquantel
WHO EMLThe only available treatment for schistosomiasis — a pyrazino-isoquinoline that causes tegumental disruption and paralytic contraction of schistosome worms. A single 40mg/kg oral dose is effective against all schistosome species. Safe, cheap, on the WHO Essential Medicines List.

Bladder cancer (SCC)
WHO/IARCSquamous cell carcinoma of the bladder — the characteristic malignant complication of chronic S. haematobium infection. IARC classified S. haematobium as a Group 1 carcinogen. Bladder SCC presents later and with worse prognosis than urothelial transitional cell carcinoma.

Female genital schistosomiasis (FGS)
WHODeposition of S. haematobium eggs in the female genital tract — causing cervical and vaginal lesions, sandy patches on cervical examination, contact bleeding, pelvic pain and infertility. Affects up to 40 million women; increases HIV susceptibility 3-fold; massively underdiagnosed.

Mass drug administration (MDA)
WHOLarge-scale distribution of praziquantel to all members of a target population (school-aged children, adults in high-transmission settings) without individual diagnosis — the primary schistosomiasis control strategy. Reduces worm burden and morbidity at population level.