Schistosoma

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.