2-7,5 cm by 0.8-2 cm by 0,5-3 mm and lives in the small intestine
and occasionally in the colon and the pylorus attached to the mucosa.
Light infection are usually asymptomatic, but heavily infected individuals
may present abdominal pain, diarrhea, malabsorption, toxemia.
# Immature unembryonated eggs are discharged into the intestine and stool .,
# Each egg becomes embryonated (3-7 weeks) in warm water.
# When fully developed, egg hatchtes to release miracidium.
# Miracidium invades a suitable planorbid snail intermediate host. In the snail the parasites undergo asexual development (generations of sporocysts, redia then cercaria ).
# Cercaria are released from the snail.
# Cervaria then encyst as metacercaria on aquatic plants [particularly Trapa natans (the water caltrop) or the water chestnut, which thrives in ponds fertilised by "night soil" (human faeces)] .
# (still part of 6 on the figure) The mammalian hosts (WE) become infected by ingesting metacercariae on the aquatic plants.
* Note: most common mammalian hosts are pigs, humans and dogs.
* Note: infection occurs if the person uses his teeth to peel the outer covering of the infected plants (the inside, the only edible part, is free of worms).
# (number 7 on the figure) After ingestion, the metacercariae excyst in the duodenum and attach to the mucosa of the jejunal and duodenal wall (intestinal wall).
# (number 8 on the figure) There they develop into adult flukes (20 to 75 mm by 8 to 20 mm) in approximately 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs).
# (back to number 1) The adults have a life span of about 6 months (some sources say up to one year). They go through sexual reproduction to make the opperculated eggs that are then dischared into the intestine and exit in stool.
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