Hydatid disease is the human infection with the hydatid cyst, the larval stage of Echinococcus granulosus.

Cosmopolitan especially in sheep raising countries.

Adults live in the small intestine of dogs and canines (the definitive host) but not man.

• Eggs are discharged in the faeces of dogs and are ingested by sheep, cattle, camels and occasionally man (the intermediate hosts).

• In the intestine of intermediate hosts, onchosphere hatches, penetrates the mucosa, passes by lymphatics or venules to blood stream to be distributed to various parts of the body where it undergoes vesiculation and develops slowly into large fluid cyst called Hydatid cyst.

• Dogs and canines are infected by eating viscera of intermediate hosts, where the scolices develop into adults.

Hydatid cyst is the diagnostic stages.

Eggs passing in stool of infecting dogs are the infective stage.

Click here to see the life cycle. 

Man is infected by ingestion of eggs through:

• Hand to mouth from fur of infected dogs while playing with them.

• Food or drink contaminated with faeces of infected dogs.