Cestoda

Echinococcus granulosus
Common name: echinococcosis ; hydatidosis or hydatid cyst.
Habitat: adult worm resides in the small intestine of dog and other canine animals. Larval form is seen in man and other intermediate hosts (sheep, goat, cattle ,pig and horse).
Morphology:
Adult worm:- It is small tapeworm measuring 3-6 mm. in length. It consist of a scolex, neck and strobila.
Scolex: It is pyriform in shape and measures about 300 Mm. in diameter. It possesses four suckers and a protrusible rostellum with two circular rows of hooklets. (30- 36 hooks)
Neck: It is short and thick.
Strobila: It consist of three segments. The first segment is immature, the second is mature and the third is gravid.
Egg:- These are indistinguishable from those of other taenia species.
Hydatid cyst:- The entire structure is called a hydatid cyst. Within the cyst, miniaturizations of the entire hydatid cyst, may occur and are referred to as daughter cysts. Both types of cysts are surrounded by a protective cyst wall and laminated layers of germinal tissue in addition, broad capsules, which lack a protective cyst wall, from the inner germinal layer. Developing scolices are found within these structures. Each scolex, once fully. Developed has the capability of developing into an adult worm when present in the definitive host A hydatid sand may evolve in the fluid of older cysts.