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