Echinococcosis is a zoonotic disease (transmitted from animals to humans) caused by the larval stage (hydatid cyst) of tapeworms. Eggs are excreted in the faeces of infected dogs and foxes and can be ingested by humans either by close contact with these animals or through contaminated food.
The most common location of cysts is the liver, but cysts may develop in almost any organ, including lungs, kidneys, spleen, nervous tissue, etc, years after the ingestion of the echinococcus eggs. In the case of cystic disease, symptoms usually appear due to the large size of the cysts. Cysts in the lungs invades tissues in a cancer-like fashion and if untreated always leads to death.
Patients are treated with surgery and the specific anti-helminthic drugs. The disease occurs in areas where dogs have access to animal inner organs, usually of sheep and cattle (intermediate hosts), containing cysts. The lung form is restricted to northern countries, where foxes abound.
Poor hand hygiene, close contact with infected animals and consumption of undercooked, unwashed food contaminated with echinococcus eggs (e.g. vegetables) are all risk factors.