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:1. Head (scolex),2. neck 3. strobilla1. Head or scolex : usually provided with

muscular suckers and crown of hooks (rostellum) to attach to intestinal wall.

General characters cont.

2.Neck3. Strobilla: the long segmented body consists

of segments 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• All worms have intermediate host except

Hymenolipis nana

Examples of class cestoda

1- Taenia sp:

Taenia saginata

Taenia solium

2- Hymenolepis sp:

Hymenolepis diminuta

3- Dipylidium caninum

4- Echinococcus granulosus

1.Taenia saginata

Taenia saginata mature segment: nearly square, bilobed ovary, scattered testis, uterus:median tube (4X)

Taenia saginata gravid segment longer than broad branched uterus filled with eggs (4X)

Egg of Taenia sp. circular,radiating double wall (H.P).

Taenia saginata cont.

• 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

2. Hymenolepis diminuta (rat tape worm)

Mature segments: broad than long characterized by 3 testis and one ovary in each segment (4X)

Gravid segments : broad than long, enlarged uterus containing eggs (4X)

2.Hymenolepis diminuta cont.

• 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

3. Dipylidium caninum (dog tape worm)

Mature segments: longer than broad,2 genital pores, testis and ovaries (4X)

Gravid segments: Longer than broad, wall deformed, enlarged uterus filled with eggs (4X)

Dipylidium caninum cont.

Egg packet

• 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

Dipylidium caninum cont.

4. Echinococcus granulosus

Adult worm:

scolex, immature, mature and gravid segments (4X)

Scolex from hydatid sand (H.P)

Echinococcus granulosus cont.

• 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