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USAID

USAID's NTD Program
USAID's NTD Program

Schistosomiasis

Life Cycle of Schistosomiasis Parasite

Chart explaining the life cycle of schistosomiasis.
Source: CDC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Step 1: When infected people urinate or defecate in a community water source, the eggs are immediately released.

Step 2 and 3: The eggs hatch and infect freshwater snails which then become the intermediate hosts.

Step 4: Inside the snails, the parasites develop and multiply.

Step 5: During its larval stage, the parasite emerges from infected snails and swims in water until it can penetrate the skin of people in contact with the water.

Step 6: Infection occurs when skin comes in contact with contaminated freshwater sources such as ponds, dams, and rivers in which certain types of snails that carry schistosomes are living.

Step 7–9: Once in the body, the larvae develop into adult male and female parasites, which pair and live together in human blood vessels for three to seven years. The female parasites release thousands of spiny eggs, some of which are passed out in the urine (in the case of urinary schistosomiasis) or feces (in the case of intestinal schistosomiasis), but some eggs remain trapped in body tissues.

Learn more about schistosomiasis: