الفهرس 
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Abstract
The females produce hundreds [African species] (Fitzsimmons et al. 2012; Protasio et al. 2012) to thousands [oriental species] of eggs per day, each ovum contains a ciliated miracidium larva, which secretes proteolytic enzymes that help the eggs to migrate into the lumen of the bladder [Schistosoma haematobium] or the intestine [other species].
The eggs are excreted in the urine or faeces and can stay viable for up to 7 days. On contact with water, the egg releases the miracidium, which searches for the intermediate host, freshwater snails, guided by light and chemical stimuli. After penetrating the snail, the miracidiae multiply asexually into multicellular sporocysts and later into cercarial larvae with embryonic suckers and a characteristic bifurcated tail (Bruno Gryseels et al. 2006; Protasio et al. 2012).
The cercariae start leaving the snail 4–6 weeks after infection and spin around in the water for up to 72 hours seeking the skin of a suitable definitive host. Cercarial shedding is provoked by light and occurs mainly during daytime. One snail, infected by one miracidium, can shed thousands of cercariae every day for months.
On finding a host, the cercariae penetrate the skin, migrate in the blood via the lungs to the liver, and transform into young worms or schistosomulae, these mature in 4–6 weeks in the portal vein, mate, and migrate to their peri-vesicular or mesenteric destination where the cycle starts again (Bloch 1980; Mansour et al. 1986; Bruno Gryseels et al. 2006).
The lifespan of an adult schistosome averages 3–5 years but can be as long as 30 years (Bas c et al. 2010).