Which organism is responsible for hydatid cyst disease?

Hydatid cyst disease is primarily caused by the organism Echinococcus granulosus, which is a tapeworm. The life cycle of Echinococcus granulosus involves canines (primarily dogs) as definitive hosts, where the adult tapeworm resides in the intestines. When these dogs excrete the eggs in their feces, they can contaminate environments where intermediate hosts, such as sheep, pigs, or humans, can ingest them. Once ingested, the eggs hatch in the intestines and can develop into larval forms that migrate to various organs, most commonly the liver and lungs, forming hydatid cysts.

These cysts are fluid-filled sacs that can grow over time and lead to symptoms depending on their size and location. In humans, the condition can lead to significant morbidity, including allergic reactions and secondary infections if the cysts rupture. Understanding the transmission and development of Echinococcus granulosus is crucial in managing and preventing hydatid cyst disease, especially in endemic areas where the lifecycle involving pets and livestock is prevalent.