Key facts

  • Four countries in the Americas are considered endemic for schistosomiasis: Brazil, Saint Lucia, Suriname, and Venezuela.
  • Approximately 25 million people are at risk of contracting the infection, and it is estimated that nearly 1.6 million school-aged children need preventive medicine (in foci in northeastern Brazil and central Venezuela).
  • Transmission of the disease is currently very low in Suriname and Saint Lucia, and these countries may interrupt transmission in the very near future.

What is schistosomiasis?

Schistosomiasis is a chronic parasitic infection caused by small worms. In the Americas, the parasitic species that causes schistosomiasis is called Schistosoma mansoni.

The main risk factor for infection is exposure through household, work, or recreational activities that take place in fresh water contaminated by the parasite. For transmission to occur, the water must be contaminated with infected feces, and a type of freshwater snail of the genus Biomphalaria (the intermediary host for the parasite) must be present. Children, adolescents, and adults who are frequently exposed to contaminated water are the populations at the highest risk.

In the Region of the Americas, schistosomiasis only manifests as intestinal symptoms such as abdominal pain, diarrhea, and bloody stools. Prolonged chronic infection can result in anemia, fibrosis of the intestinal veins and the liver, spleen enlargement, and in serious cases, may lead to neurological complications and even death. Deaths from schistosomiasis in children and adults are reported each year.

The main risk factors for infection with S. mansoni are associated with living in extreme poverty with no access to improved basic sanitation facilities and drinking water.

This disease is prevented through the mass administration of antiparasitic drugs to populations living in high-risk areas, as well as improved access to clean water and sanitation, education in good hygiene habits, and control of snails.

PAHO/WHO's response

  • In 2012, the WHO member countries approved the goal of eliminating the transmission of schistosomiasis (WHA 65.21).
  • PAHO/WHO works with endemic countries to obtain medicine donations and diagnostic tests needed to interrupt transmission and eliminate schistosomiasis.
  • PAHO/WHO provides technical cooperation for the surveillance, prevention, and control of schistosomiasis and helps countries prepare to obtain verification of elimination of transmission.