Infection from contaminated water

Urogenital schistosomiasis (or urogenital bilharzia) is caused by Schistosoma haematobium. Its life cycle involves humans and an intermediate host, the snail, a freshwater mollusk.
The snail is infected by larvae that have recently hatched from Schistosoma haematobium eggs. Four to six weeks after infection, it releases immature forms (cercariae) of the parasite into freshwater. The optimal temperature for infection of the snail is 20 to 30°C.
Humans become infected when cercariae penetrate healthy skin during contact—even brief contact—with contaminated freshwater (rivers, lakes, marshes, ponds, etc.).
In the weeks following infection, the parasites mature and migrate through the bloodstream to the perivesical venous plexuses (invasion phase). After 10 to 12 weeks, female parasites lay eggs that are excreted in the urine. Without treatment, egg excretion can continue for several years.

Urogenital schistosomiasis is endemic in intertropical Africa, Madagascar, and the Middle East. In France, cases of schistosomiasis are diagnosed primarily in tourists, expatriates, and migrants from endemic areas.

Since a local transmission cluster has been identified in Southern Corsica, Santé publique France’s priorities are to monitor the extent of disease transmission at known contaminated sites and to detect any new transmission sites.

Intestinal schistosomiasis, which is not present in France, is caused by five other species of schistosomes:

• Schistosoma mansoni, the second most common species after S. haematobium, found in Africa, the Middle East, the Caribbean, Brazil, Venezuela, and Suriname

• Schistosoma japonicum in China, Indonesia, and the Philippines

• Schistosoma mekongi, found in Cambodia and the Lao People’s Democratic Republic

• Schistosoma guineensis and the related species S. intercalatum in the rainforests of Central Africa.

Schistosomiasis caused by S. mansoni has been considered eradicated from the French West Indies since the late 1980s.

Clinical and Laboratory Diagnosis

The symptoms of urogenital schistosomiasis are variable and depend on the stage of the disease.
The penetration of cercariae (immature forms of the parasite) may be accompanied by itching and a transient rash.
During the invasion phase, in the weeks following infection, immuno-allergic reactions may occur.
In the chronic phase, approximately 2 months after infection, symptoms are related to the body’s inflammatory response to the parasite’s eggs.

Urogenital schistosomiasis can then lead to:

• hematuria (blood in the urine)

• genital lesions, gynecological bleeding, or blood in the semen, pain during sexual intercourse

• at a more advanced stage, fibrosis of the bladder and urethra is common, as well as kidney damage

• Bladder cancer is a possible complication in the late stages.

Bilharzia can be diagnosed by:

• serology: several techniques are used, including indirect immunofluorescence, indirect hemagglutination (IHAT), ELISA, and Western blot

• search for parasite eggs in urine (parasitological urine examination) or stool

• PCR in urine or stool

Possible complications in the absence of treatment

The progression of schistosomiasis over several years can eventually lead to serious complications (obstructive or even neoplastic damage to the urinary tract and fertility problems). In children, it can cause anemia, stunted growth, and impaired learning ability.

Effective treatment

Treatment for Schistosoma haematobium schistosomiasis is simple, inexpensive, and effective, and relies on praziquantel.
Diagnosis and treatment of schistosomiasis make it possible to:

• at the individual level, prevent the disease from becoming chronic

• at the community level, to break the disease cycle and thus prevent new cases