Schistosomiasis

Schistosomiasis (synonyms: schistosomiasis; ICD-10-GM B65.-: Schistosomiasis (bilharzia)) is a worm disease caused by trematodes (sucking worms) of the genus Schistosoma (couch flukes).

The disease is mainly caused by five human pathogenic trematodes: Schistosoma (S.) haematobium, S. mansoni, S. japonicum, S. intercalatum and S. mekongi.

Pathogen reservoirs are snails as intermediate hosts in freshwaters (rivers, lakes), from which schistosoma larvae, called cercariae, are released.

Occurrence: Infection occurs in Africa, Arabian Peninsula, South America, Caribbean, Asia incl. regions in China.

Pathogen Localization Region Countries with pronounced distribution Additional pathogen reservoirs
Schistosoma haematobium Pathogen of urogenital schistosomiasis (bladder bilharzia). Africa, Near and Middle East Algeria, Libya, Morocco, Tunisia, Saudi Arabia, much of black Africa; Turkey, Iran, Iraq, Yemen, Lebanon, Madagascar, Mauritius, Syria, IndiaIndividual cases: Bathing on the Cavu/Cavo River in South Corsica. Monkeys (minor importance)
Schistosoma intercalatum Pathogen of intestinal or gut schistosomiasis. West Africa Regionally in Cameroon, Gabon and the Congo, Tanganyika, Central African Republic. Cattle, horses, antelopes, gazelles.
Schistosoma mansoni Africa, Arabian Peninsula, South America (Brazil), occasional Caribbean. large parts of black Africa, Egypt, Saudi Arabia, Oman, Yemen, Libya, Madagascar, Brazil, Suriname, Venezuela, Caribbean Rodents, monkeys (of minor importance).
Schistosoma japonicum East Asia China, Japan, Indonesia (Sulawesi), Taiwan and the Philippines, sporadically Japan. Cattle, dogs, rats
Schistosoma mekongi Southeast Asia Laos and Cambodia along the Mekong River, Thailand, Malaysia Dogs

The transmission of the pathogen (infection route) occurs in fresh waters. The cercariae can penetrate the human skin on contact.Infection via contaminated drinking water is also possible!

The entry of the pathogen is percutaneous (through the skin).

Human-to-human transmission: No The incubation period (time from infection to onset of disease) is usually 6-48 hours until the onset of cercarial dermatitis. 2-8 weeks to acute schistosomiasis (Katayama fever).

Schistosomiasis is one of the most important tropical diseases worldwide after malaria.

Course and prognosisTwo stages can be distinguished in the course of the disease:

  • Penetration stage and acute schistosomiasis:
    • After penetration of the cercariae, there is immediate itching (sometimes there are red, itchy patches or papules at the site of entry of the pathogens; cercarial dermatitis).
    • After initial infection with S. japonicum, S. mekongi, rarely with S. mansoni, very rarely with S. haematobium, a highly febrile, sometimes life-threatening clinical picture may develop (see below sequelae: Katayama fever).
  • Chronic schistosomiasis: infestation of various organs, such as urinary bladder (urogenital schistosomiasis), intestine (intestinal or intestinal schistosomiasis) and liver and spleen (hepatolienal schistosomiasis), lungs and central nervous system with corresponding symptoms.Infections with S. intercalatum can lead to involvement of the genital tract and rectal bleeding.

The disease often leads to death if untreated. With timely therapy, there are good prospects of cure.

In Germany, the disease is not reportable under the Infection Protection Act (IfSG).

Guideline

  1. S1 Guideline: diagnosis and therapy of schistosomiasis (bilharzia). (AWMF register number: 042-005), October 2017 long version.