Cestodes Lecture 5 PDF

Basic and Laboratory parasitology (HLPR-301) Fall 2024-2020 Cestodes Lecture 5 Ass.Prof. Esraa Moneer  Helminths Multi-cellular, Bilaterally symmetrical &...

Basic and Laboratory parasitology (HLPR-301) Fall 2024-2020 Cestodes Lecture 5 Ass.Prof. Esraa Moneer  Helminths Multi-cellular, Bilaterally symmetrical & Elongated, flat or rounded animals. Phylum Platyhelminthes Phylum Nematoda (Flat Worms) (Round Worms) Trematoda Cestoidea  Cestoidea (Tape worm) Pseudophyllidea Cyclophyllidea D. latum Taenia Echinococcus granulosus Hymenolepis nana General morphology of Cestodes  General morphology of Cestodes 1 Adults are flat & segmented, varying in length from few mm to several meters. 2 The body is divided into : Head {Scolex} : Provided with suckers for attachment with or without rostellum & hooks. Neck : Is the region of growth. Proglottids {Strobila} ; differentiated into immature, mature and gravid segments containing the uterus filled with eggs.  General morphology of Cestodes 3 Cestodes have neither a body cavity nor an alimentary tract. 4 Nutrients are absorbed through their cuticle or tegument which have also a protective function by secreting substances that inactivate the host digestive enzymes. 5 They are hermaphrodites.  LIFE CYCLE OF CESTODES Adults are parasites of the small intestine of man or animals (DH). They require one or two IH with the exception of H. nana which has only one host acting both as IH &DH. Gravid segments or eggs of cestodes are passed in the faeces of their DH. Cyclophyllidea Taenia Spp Taenia saginata Taenia solium  Habitat : Adult worms live in the small intestine of Man.(Definitive host)  Morphology The adult T saginata measures 4-10 meters and usually has from 1000-2000 proglottids. T solium is shorter 3-8 meters and less number of segments (1000).  Morphology The scolex Taenia saginata: the scolex is quadrate, unarmed and has 4 strong suckers. Taenia solium: the scolex is globular with rostellum armed with double rows of hooks.  Life cycle : - Diagnostic stage : Gravid segments or mature eggs in the faeces of the definitive host. Taenia egg : spherical, have thick striated brown embryophere surrounding hexacanth embryo or oncosphere. Gravid segments : The gravid segments of T. saginata is more elongate & rectangular than that of T. solium. The gravid segments of T. saginata has uterus with more lateral branches than T. solium. - Intermediate host : Cattle for T. saginata. Pig for T. solium.  Life cycle : - Infective stage : Cysticercous bovis in muscles of cattle for T. saginata. Cysticercous cellulosae in muscles of pig for T. solium. - Mode of infection : By ingestion of undercooked beef meat containing cysticercous bovis in ( T. saginata ). By ingestion of undercooked pork meat containing cysticercous cellulosae in ( T. solium ).  Taenia Egg  Cyclophyllidea Echinococcus Spp Echinococcus granulosus  Habitat : Adult worms (minute worm 3-6 mm in length) live in the small intestine of dogs and other carnivorous animals.  Morphology - The scolex is pyriform, provided with 4 suckers armed with hooks. - The neck is short and followed by three proglottids (immature, mature and gravid).  Life cycle : Infective stage : Eggs passed in the faeces of definitive host. (egg similar to Taenia egg ) Intermediate host : herbivorous animals ( sheep, goat ….) or man. Diagnostic stage : Hydatid cyst in different organs. Mode of infection : by ingestion of food contaminated with eggs.  Cyclophyllidea Hymenolepis nana ( The dwarf tap worm ) Hymenolepis nana  Habitat : Adult worm lives in the small intestine of Man.  Morphology - This is the smallest tapeworm infecting man(20-60 mm). - The scolex is rhomboidal with 4 suckers armed with spines. - The neck is long and slender, followed by more than 100 segments, which are broader than long.  Life cycle : Infective stage : Eggs.( mature eggs immediately infective once formed). Diagnostic stage : Eggs in the faeces of the definitive host. (Egg : oval or spherical, with two thin shells. The inner shell has two knobs at opposite sides from which 4-8 filaments arise & run in the space between the outer and inner shell. Mode of infection: by ingestion of the eggs in contaminated food or drink or by auto-infection. Hymenolepis nana egg Thank you