Date: July 16, 2019

Mainly cloudy with 60 percent chance of showers. Risk of a thunderstorm this afternoon. Wind southwest 20 km/h gusting to 40. High 29. Humidex 37. UV index 7 or high.


Feels like 36C

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Schistosomiasis (Bilharzia)

This page was reviewed or revised on Thursday, July 21, 2016 3:57 PM

Environmental Health & Prevention Services

What is it?

  • It is a parasitic infection acquired through contact with freshwater throughout the tropics and subtropics
  • The major forms in humans are caused by water-borne flatworms or blood flukes called schistosomes


  • Schistosomes lived in certain freshwater snails, which release large numbers of tiny free-swimming larvae (called cercariae)
  • These cercariae penetrate unbroken skin of a person who comes in contact with infested water and migrate to veins around the liver or bladder where mature worms produce eggs
  • Adult worms can live up to 15 years and produce large numbers of eggs that exit the body through urine or feces


  • A few hours after contact with schistosomes, fewer than 10% of people may experience tingling of the skin with a rash where the cercaria enter the boy (“swimmers itch”), and usually resolves within 24 hours
  • Weeks later, once the adult worms begin to produce eggs, the person may develop flu-like symptoms, with fever, tiredness, respiratory symptoms (coughing, wheezing, shortness of breath), diarrhea and hives
  • Long-term consequences include severe liver disease, kidney failure, and bladder cancer


  • Avoid bathing, swimming, wading, boating, or rafting in cercariae-infested waters
  • Risk is highest along lake shores, slow-moving streams, and irrigation ditches that contain the snail host
  • Even brief water exposure can lead to infection since the cercariae can penetrate intact skin within 30 seconds to 10 minutes
  • If water exposure cannot be avoided, try to wear protective footwear or clothing and apply appropriate insect repellent
  • Quickly dry exposed skin and clothing, as cercariae cannot survive drying

Where is it found?

  • Nile valley, east Africa
  • West Africa (especially Savanna)
  • Lake Malawi
  • Lake Victoria
  • Along the Euphrates and Tigris rivers in the Middle East
  • Eastern Mediterranean
  • The Caribbean
  • South America - Brazil
  • Southeast Asia