Life cycle of echinococcus granulosus
Echinococcus granulosus passes it's life cycle in two host;
1. Definitive host
2. Intermediate host
1. Definitive host
Adult worms live in small intestine of these animals and discharge egg in their faeces.
Dog is optimum definitive host, but wolf, fox and jackal also act as definitive host.
2. Intermediate host
The larval stage is present in these animal including man, giving rise to hydatid cyst.
Egg are discharged in faeces of definitive host and are swallowed by intermediate hosts.
The man get infected due to intimate handling of infected dog.
After ingestion, embryo are hatched out in small intestine and penetrate wall of intestine.
They enter into liver through portal vein.
Hydatid cysts develop into liver. The embryo develop slowly into hydatid cyst.
Some on embryos enter pulmonary circulation, larva reaches lungs and curculate various part of body.
Thus, larva form hydatid cyst wherever they settle.
These hydatid when ingested by dog, are capable of growing into adult worm in intestine.
Natural cycle of parasite is maintained between sheep and dog.
1. Infected egg from dog's stool are swallowed by human due to close handling of infected dogs. Other host infected eating contaminated grass and vegetation.
2. Egg passes through stomach into small intestine, where embryo hatch out.
3. Embryo penetrate wall of intestine and carried to liver and other organ.
4. Embryo develop into hydatid cysts.
5. Hydatid cyst contain thousand of Scolices.
6. Hydatid cyst ingested by dog.
7. Each scolex develops into adult worm (male and female)
8. Adult worm in small intestine of definitive host (dog).
9. Egg released in faeces.
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