Class Cestoda
Jan 04, 2016
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 solium2- Hymenolepis sp: Hymenolepis diminuta Hymenolepis nana3- Dipylidium caninum4- 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
Taenia solium scolex: rostellum with 2 rows of hooks (spines) and 4 suckers
Cysticercus in section of muscle
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
Scolex showing 4 suckers
Egg packet
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