CESTODES

CESTODESGeneral 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 15-20 ).

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 its a mature egg having embryo with six hooks.Definitive and intermediate host: HumanInfective stage: Larvated eggWe 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 (3000-4000) segments. Consists of head, immature segments, mature segments and gravid segments.

Egg: oval, yellowish in color, immature and operculated.Definitive host: Human, 1st intermediate host: Cyclops, 2nd intermediate host: Fish.Infective stage: larva (plerocercoid) in fish flesh (as salmon)