PARA LEC: CESTODES 1

• Flatworms are collectively called the FLATWORMS
• They are dorsoventrally flattened and bilaterally symmetrical
• Flatworms are covered by a membrane called tegument
• Most flatworms are hermaphroditic, except for Schistosoma sp.
• Flatworms include Tapeworms and Flukes
• They are multicellular animals characterized by a flat, bilaterally symmetric body
• Flatworms are hermaphroditic, having both male and female reproductive organs in the same individual
• The overall size of flatworms varies greatly, ranging from 1 mm to 20 meters or longer
• The classes Cestoda (tapeworms) and Trematoda (flukes) contain species parasitic to humans
• Cestodes are tapeworms with flat, segmented bodies of various lengths
• Each proglottid of a tapeworm develops both male and female reproductive organs, with mature eggs developing in the most distal proglottids
• Tapeworms have no circulatory system or digestive tract
• Tapeworms are diagnosed by finding eggs or proglottids in the feces
• Habitat of adult tapeworm: intestine of the Definitive Host (DH)
• Taenia species (example)
• Adult worms are seen in the intestine
• Proglottids contain male and female parts
• Eggs have 6 hooked embryos
• Tapeworms have a ribbon-like body, flat, and require an intermediate host
• Cestodes consist of three basic portions: Scolex, Neck (germinal portion), and Strobila (immature, mature, gravid proglottids)
• Scolex is for attachment, with a rostellum armed with hooks and suckers
• Strobila segments bud from behind the scolex and are immature, then mature and fill with eggs, becoming "gravid" proglottids
• Immature proglottids have undifferentiated reproductive organs, while mature proglottids have differentiated reproductive organs
• Gravid proglottids have a uterus with lateral branches filled with eggs
• Species of Cestoda that require a vertebrate intermediate host include Taenia solium, Taenia saginata, and Echinococcus granulosus
• Species of Cestoda that require an invertebrate intermediate host include Dipylidium caninum, Hymenolepis diminuta, and Raillietina garrisoni
• Species of Cestoda that may or may not require an intermediate host include Hymenolepis nana
• Species of Cestoda that infect humans in their larval stages include Echinococcus granulosus, Echinococcus multilocularis, Taenia solium, and Diphyllobothrium latum
• Binomial names and common names of Cestoda species
• Taenia saginata - Beef Tapeworm
• Taenia solium - Pork Tapeworm
• Taenia multiceps - Coenurus Tapeworm
• Echinococcus granulosus - Hydatid Tapeworm
• Echinococcus multilocularis - The Multiloculate or Alveolar Hydatid Tapeworm
• Hymenolepis nana - Dwarf Tapeworm
• Hymenolepis diminuta - Rat Tapeworm
• Dipylidium caninum - Double-pored Tapeworm
• Diphyllobothrium latum - Broad Fish Tapeworm
• Classification of Cestoda into Pseudophyllidean and Cyclophyllidean
• Pseudophyllidean: Scolex is almond/spatulate with 2 slit-like grooves, uterus has no branching with pores, and eggs are operculated giving rise to ciliated larvae