Schistosomiasis

SchistosomiasisPraziquantel is the recommended treatment against all forms of schistosomiasis. It is effective, safe, and low-cost. Even though re-infection may occur after treatment, the risk of developing severe disease is diminished and even reversed when treatment is initiated and repeated in childhood.

Key facts

  • Schistosomiasis is an acute and chronic disease caused by parasitic worms.
  • People are infected during routine agricultural, domestic, occupational, and recreational activities, which expose them to infested water.
  • Lack of hygiene and certain play habits of school-aged children such as swimming or fishing in infested water make them especially vulnerable to infection.
  • Schistosomiasis control focuses on reducing disease through periodic, large-scale population treatment with praziquantel; a more comprehensive approach including potable water, adequate sanitation, and snail control would also reduce transmission.
  • Estimates show that at least 220.8 million people required preventive treatment for schistosomiasis in 2017, of whom more than 102.3 million were reported to have been treated.

Schistosomiasis is a parasitic disease that leads to chronic ill-health. People infected with schistosomes expel the parasite’s eggs in their faeces or urine depending upon the type of the infecting parasite. In communities where no proper latrines or sanitation exist, freshwater resources in these communities may become contaminated with faeces or urine containing the eggs. Eggs hatch when they come in contact with water, thus releasing larvae called miracidia. If miracidia find the right type of snail, they use it to multiply in several cycles, eventually producing thousands of new parasites, called cercariae, which are then released from the snails to the surrounding water. When humans come into contact with water-containing cercariae, cercariae penetrate the skin and infect those humans.

Schistosomiasis is characterized as either intestinal or urogenital, depending on where the adult flukes are located. In intestinal schistosomiasis, adult worms occupy mesenteric veins, and their eggs pass into the lumen of the intestine and reach the faeces. There are four species that cause intestinal schistosomiasis: S. intercalatumS. japonicumS. mansoni and S. mekongiS. haematobium causes urogenital schistosomiasis, and adult worms reside in veins draining the urinary tract, and their eggs pass out of the body in the urine.

An estimated 207 million people may have schistosomiasis in the world. The disease is endemic in tropical and subtropical areas. It is most prevalent in sub-Saharan Africa, where more than 90% of those infected live.

In the Eastern Mediterranean Region, Somalia and Sudan remain the most endemic countries. The disease is considered eliminated in Islamic Republic of Iran, Lebanon, Morocco and Tunisia. Low endemicity has been reached in Egypt, Iraq, Jordan, Libya, Oman, Saudi Arabia and Syrian Arab Republic.