Medical Parasitology

Cestodes of Mammals

The cestodes (or tapeworms) form a group of worms, exhibiting two unmistakable morphological features; they all possess flat, ribbon like bodies and lack an alimentary canal. Adult tapeworms usually inhabit the alimentary canal of their hosts (though they occasionally are found in the bile or pancreatic ducts) and attach themselves to the mucosa by means of a scolex. Despite the lack of a digestive system they do absorb food from the hosts intestine; thereby providing the tapeworms a habitat that is associated with high nutritional levels, feeding the tapeworms high growth rate. Larvae on the other hand show a wide range of habitat preferences, being found in almost any organ of both vertebrate and invertebrate hosts. Clinically important cestodes pathogenic to man are Tenia solium (pork tapeworm), T. saginata (beef tapeworm), Diphyllobothrium lattum (fish or broad tapeworm), Hymenolepis nana (dwarf tapeworm) and Echinococcus granulosus and E. multilocularis (hydatid).