CESTODES

General characteristics: Both sexes are seen in the same body. They are flat segmented worms, which inhabits the small intestine. Part of the segments may pass with the stool. All have the same morphology : 1- Head (Scolex). 2- Short neck. 3- Segmented body.

1- Taenia SP. Eggs of both species are similar to each other; they can be differentiated by the adult stage. The egg is spherical, brownish in color, having embryo with six hooks surrounded by thick wall. Adult: A- Taenia Saginata: the scolex have 4 large suckers, without hooks, the gravid segment shows characteristic branching of the uterus ( from ). B-Taenia Solium: the scolex have 4 suckers with hooks, the gravid segment contains less than 10 branches.

Definitive host: Human T. Saginata intermediate host: cattles, and the infective stage is: cysticercous bovis T. Solium intermediate host: pigs, and the infective stage is: cysticercous cellulosae

2- Hymenolepis nana: The commonest cestode in children. Egg: ovoid in shape, colorless having two shells separated by a space. Inside this space 4-8 filaments it’s a mature egg having embryo with six hooks. Definitive and intermediate host: Human Infective stage: Larvated egg We will not see the adult in the lab.

3- Echinococcus granulosus: Normally not a human cestode its habitat is the small intestine of the dogs. Human act as an intermediate host. Adult: have scolex, neck, one immature segment, one mature segment and one gravid segment. Egg: we will not see it in the lab.

4- Diphyllobothrium latum: Adult: 10 meters long ( ) segments. Consists of head, immature segments, mature segments and gravid segments. Egg: oval, yellowish in color, immature and operculated. Definitive host: Human, 1 st intermediate host: Cyclops, 2 nd intermediate host: Fish. Infective stage: larva (plerocercoid) in fish flesh (as salmon)