Bilharzia (Urinary Schistosomiasis)


Bilharzia is a disease caused by an infection with a parasite known as Schistosoma haematobium. The term schistosomiasis refers to an infection with one of the Schistosome species of parasites, each of which have an affinity for a different organ. However, the term bilharzia primarily refers to urinary schistosomiasis. This disease is mainly found in Africa, South America, Caribbean, and Middle East especially Egypt, and in certain parts of China. Men are more often affected than women and this may largely be due to differences in behavior as the infection is contractes by swimming in rivers.


The initial stage is also known as swimmer’s itch as it is experienced shortly after swimming in the infected water. The area of the skin through which the parasite gains entry develops an itchy rash which can persist for around 5 days. High grade fever with chills in the evenings, sweating and breathlessness or asthma can occur after around 4 to 12 weeks of initial stage. Typically one may see a rise in the white cell count (leukocytosis) responsible for the fever and eosinophils or allergy cell (eosinophilia) in the blood during this stage.

Symptoms usually subside and after several months the ova (eggs) of the parasite are released and cause the typical sign of intermittent, painless passage of red blood cells in the urine (hematuria), increased frequency of urination and pain during urination is experienced. Usually, this causes concern and most cases are detected at this stage.

Untreated bilharzia can lead to :

  • Nodules (small swellings) and ulcers may form in the bladder mucus membrane.
  • Bacterial infection of the urinary bladder (bacterial cystitis).
  • Bladder stones (urinary calculi).
  • Stricture formation in the urethra is often seen along with a fistula (opening between the two surfaces of the bladder).
  • Long standing cases may develop into tumors of the bladder which may be benign or malignant (cancer).


The causative organism completes its life cycle in man and a snail, Bulinus truncatus. This is a freshwater snail present in marshes or slow running fresh water. Ova or eggs of the parasite Schistosoma haematobium are present in the water contaminated by urine or feces of people suffering from this infection. These eggs hatch in the water and the parasite enters the snail. The parasite grows further inside the snail’s body and leaves upon reaching the adult stage thereby contaminating the water.

Swimming in infected water introduces the parasite into the human body through the skin. Schistosoma haematobium has an affinity for the veins of the body and develop into male worms and female worms. Once they reach the urinary bladder, the female worm’s lay hundreds of ova (eggs) which blocks the opening of bladder.


Diagnosis is made with examination of the urine to detect the parasite and cystoscopy is done to visualize the bladder for the presence of disease. Medication to treat bilharzia includes :

  • Oral praziquantel and metrifonate to treat smaller lesions.
  • Ulcers and nodules may be treated with light diathermy coagulation.
  • Surgery is done to remove the tumors of the bladder.

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