Scientific Name: Schistosoma mansoni
Males and females have different morphologies. Adult worms are bilaterally symmetrical with a digestive system and oral suckers on both ends of the body for attachment to the host and stabilization.
Stool and urine samples are viewed under the microscope to detect the parasite’s eggs. Sometimes the host has no symptoms, but it is possible for the host to react to the worm with fever, cough, abdominal pain, and diarrhea.
- Eggs are relaesed from infected human through urine or feces
- Eggs hatch and release miracidia, which are free swimming larvae
- Miracidia penetrate snail tissue
- Schistosoma continue developing in snail to the sporocyst stage
- Schistosoma develop to become cercariae which are released from the snail into water. Cercariae are free swimming
- Cercariae penetrate skin of a new human host
- Cercariae lose tails and enter the schistosomulae stage
- Schistosomulae migrate using circulation to the lungs, the heart, and then the liver
- Schistosomulae leave the liver when thet are mature
- Male and female adult worms mate and lay eggs which are shed either in stools or in the urine
- Dogs serve as a reservoir host, but it is primarily a human parasite and not considered zoonosis
- Undergoes sexual reproduction in humans and asexual repriduction in snails
- Compatibility with snail intermediate host can be affected by toxicity of water caused by pollutants and pH changes
- Pollutants in the water can also affect the free swimming cercariae and make it difficult for them to reach the definitive human host
- There are drugs which have been developed which cause deformations to the worms which allow the host immune system to attack them
This parasite is distributed across sub-Saharan Africa and in some South American countries.