Schistosoma

PARASITES TREMATODES

Schistosoma Species

• The schistosomes are also known as "blood-flukes".
• There are several important species producing serious human and animal disease in the tropics.
• The pathology is mostly associated with the passage of eggs through the liver, urinary bladder or intestinal wall (depending on the predilection site of the fluke).
• As their common name suggests, the adults live in blood-vessels.
• Unusually for a trematode, the sexes are separate.
• The smaller female lies enveloped by the male.
• The eggs of most species have spikes to assist their passage through host tissue to get into faeces or urine (depending on predilection site).
• The intermediate hosts are water snails.
• On release, the cercariae swim in water and actively seek their final host, which they enter by skin penetration - there is, therefore, no metacercaria stage.