Class Cestoda

General characters All tape worms consist of long, multi-segmented body. Cuticle of the body is provided with pores through which the worm takes its nutrients (no digestive system) They are hermaphroditic. The adult worm is divided into 3 distinct parts: Head (scolex), neck and strobilla Head or scolex : usually provided with muscular suckers and crown of hooks (rostellum) to attach to intestinal wall.

General characters Strobilla: the long segmented body consists of segments which are of three types (i) the immature segments which follow the neck region (ii) the mature segments containing both sex organs and are responsible for reproduction (iii) the gravid segments filled with fertilized eggs. Eggs :contain hexacanth embryo The worms have intermediate host except Hymenolipis nana

Examples of class cestoda 1- Taenia sp: Taenia saginata Taenia solium 2- Hymenolepis sp: Hymenolepis diminuta Hymenolepis nana 3- Dipylidium caninum 4- Echinococcus granulosus

Taenia saginata Taenia saginata mature segment: nearly square, bilobed ovary, scattered testis, uterus:median tube (magnifier) Taenia saginata gravid segment longer than broad branched uterus filled with eggs (magnifier) Egg of Taenia sp. circular,radiating double wall (H.P).

Taenia saginata Location of adult: small intestine of man Intermediate host : cattle Infective stage : cysticercus bovis Mode of transmission: eating insufficiently cooked meat containing cysticercus bovis Diagnosis: eggs & gravid segments in stool Disease: Taeniasis

Taenia solium Cysticercus in section of muscle Taenia solium scolex: rostellum with 2 rows of hooks (spines) and 4 suckers

Taenia solium Location of parasite: Taeniasis: Adult worm in small intestine of man Cysticercosis: Cysticercus (larval stage) in muscle or brain of man Intermediate host : Taeniasis: Pigs Cysticercosis: man Infective stage : Taeniasis: cysticercus cellulosae Cysticercosis: eggs Mode of transmission: Taeniasis: Eating undercooked pork containing cysticercus cellulosae Cysticercosis: Autoinfection with eggs Diagnosis: Taeniasis: eggs & gravid segments in stool Cysticercosis is diagnosed by X ray Disease: Taeniasis, cysticercosis

Hymenolepis diminuta (rat tape worm) Mature segments: broad than long characterized by 3 testis and one ovary in each segment (magnifier) Gravid segments : broad than long, enlarged uterus containing eggs (magnifier)

Hymenolepis diminuta Location of adult: small intestine of rat occasionally man Intermediate host: rat flea Infective stage: cysticercoid Mode of transmission: ingestion of rat flea containing cysticercoid Diagnosis: eggs and gravid segments in stool Disease: hymenolepiasis

Hymenolepis nana Mature segments: broad than long characterized by 3 testis and one ovary in each segment (L.P) Gravid segments : broad than long, enlarged uterus containing eggs (L.P)

Hymenolepis nana Very small 25 mm Location of adult: small intestine of man Intermediate host: none Infective stage :eggs Mode of transmission: eating food contaminated with eggs or autoinfection Diagnosis: eggs in stool

Dipylidium caninum (dog tape worm) Mature segments: longer than broad, 2 genital pores, testis and ovaries Gravid segments: Longer than broad, wall deformed, enlarged uterus filled with eggs

Dipylidium caninum Egg packet Scolex showing 4 suckers

Dipylidium caninum Location of adult: small intestine of dogs, occasionally man Intermediate host: dog flea Infective stage: cysticercoid Mode of transmission: ingestion of dog flea containing cysticercoid Diagnosis: egg packet in stool Disease: Dipylidium caninum infection

Echinococcus granulosus Adult worm: scolex, immature, mature and gravid segments (L.P) Scolex from hydatid sand

Echinococcus granulosus Location of adult: small intestine of dogs Location of hydatid cyst : liver,lung, CNS and bone in man, cattle and sheep Intermediate host: cattle, sheep (man is an end stage intermediate host) Infective stage: eggs in feces Mode of transmission: man is infected by ingestion of eggs in dog feces Diagnosis: identification of hydatid cyst by X ray Disease: hydatid disease