The Life Cycle of the Bilharzia Parasite

Question 1

What is the life cycle of the bilharzia parasite?

Answer 1

• Cercariae (parasitic larvae) penetrate skin of human (primary host)
• They shed their tails and penetrate surface blood vessels of skin
• Larvae enter bloodstream and move to liver
• Adult worms develop in liver and mate
• Worms move to blood vessels of intestinal canal or bladder where females lay eggs
• Eggs bore through vascular walls and end up in intestinal canal or bladder
• Large number of eggs released in urine or faeces
• Eggs burst open in freshwater and release miracidia
• Miracidia enter freshwater snail (intermediate host) and develop into cercariae
• Freshwater snail dies and cercariae are released in water
• The cycle continues…