Schistosomiasis: Causes, Symptoms and Treatment

Schistosomiasis is also known as “snail fever”.

Which is a parasitic disease produced by freshwater snails infected by one of the five varieties of the Schistosoma parasite. It is found mainly in tropical and subtropical climates, affecting 240 million people in a maximum of 78 countries, with the highest prevalence in Africa and ranking second after malaria as the most common parasitic disease.

Causes of Schistosomiasis

Schistosomiasis is transmitted by contact with contaminated fresh water (lakes, lagoons and rivers) inhabited by snails carrying the parasite. Swimming, bathing, fishing, and housework, including laundry and livestock grazing, can put people at risk of contracting the disease. The larvae emerge from the snails, swim in the water until they come into contact with the individual and penetrate the skin. Once inside the body, they become male and female worms mating and coexisting in the blood vessels for years.

Some Schistosoma eggs remain trapped in the body and migrate to specific organs (depending on the type of parasite) where they can cause significant damage. Urinary schistosomiasis leads to scarring, tearing of the bladder and kidneys, causing bladder cancer. Intestinal schistosomiasis develops slowly, causing abdominal hemorrhage; Enlargement of the liver, lungs, spleen and intestines. An important indicator of the disease is blood in the urine and / or stool.


The symptoms of the disease vary depending on the type of worm and the location of the parasite inside the body, which include:

  • Initial itching and rash at the site of infection.
  • Frequent, painful or bloody urine.
  • Abdominal pain and diarrhea with blood.
  • Anemia.
  • Fever, chills and muscle aches.
  • Inflammation and scarring of the bladder.
  • Inflammation of lymph nodes
  • Enlargement of the liver or spleen.
  • Secondary blood disorders in case of damage to the colon.
  • If the infection persists, bladder cancer may develop in some cases.
  • Children with repeated infections can develop anemia, malnutrition and learning problems.

How it is transmitted

Parasites enter the skin during contact with fresh water containing contaminated snails. The larvae migrate to the blood vessels where they mate producing eggs which travel to the bladder or intestines and pass to the urine or feces. Others remain trapped in the body and cause damage to internal organs.

Treatment for Schistosomiasis

A vaccine against schistosomiasis is currently in the early stages of development. Praziquantel is the primary form of treatment. A single dose of praziquantel has been shown to reduce the severity of symptoms in cases of subsequent re-infection.

As a preventive method, the most advisable are education campaigns as well as about the risks of getting infected by bathing in freshwater lakes and ponds.