Introduction to Flukes.
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The Flukes. (Trematoda).
All flukes are either internal or external parasites of vertebrates. They are of extreme economic importance, especially in tropical developing countries. Bilharzia, or Schistosomiasis, is a disease caused by species of the blood-fluke Schistosoma, and is at present the world's second most prevalent infectious disease -- second only to malaria.
Areas such as Africa (especially Egypt), South America and China are worst affected.
Flukes have flattened, leaf-like bodies, with one or two suckers, through which most species are able to feed. Tapeworms also have suckers, but when present, they serve only for attatchment. The life cycle of flukes differs from one species to another, but always involves a number of larval stages, one of which is invariably spent in a freshwater mollusc -- usually a snail.
The classic fluke of the textbooks is the liver fluke, Fasciola hepatica, which infects a wide range of domestic and wild animals, including sheep and humans.
Click for diagrams of Fasciola showing (a) reproductive system, and (b) nervous and reproductive systems.
The miracidium larva (the first larval stage) of Fasciola is seen in the process of hatching in the movie sequence below. The original footage was shot on 16mm Kodachrome with synchronized electronic flash.