Echinococcosis is a parasitic disease of tapeworms of the Echinococcus type. The two main types of the disease are cystic echinococcosis and alveolar echinococcosis. Less common forms include polycystic echinococcosis and unicystic echinococcosis.

The disease often starts without symptoms and this may last for years. The symptoms and signs that occur depend on the cyst's location and size. Alveolar disease usually begins in the liver, but can spread to other parts of the body, such as the lungs or brain. When the liver is affected, the patient may experience abdominal pain, weight loss, along with yellow-toned skin discoloration from developed jaundice. Lung disease may cause pain in the chest, shortness of breath, and coughing.

The infection is spread when food or water that contains the eggs of the parasite is ingested or by close contact with an infected animal. The eggs are released in the stool of meat-eating animals that are infected by the parasite. Commonly infected animals include dogs, foxes, and wolves. For these animals to become infected they must eat the organs of an animal that contains the cysts such as sheep or rodents. The type of disease that occurs in human patients depends on the type of Echinococcus causing the infection. Diagnosis is usually by ultrasound though computer tomography (CT) or magnetic resonance imaging (MRI) may also be used. Blood tests looking for antibodies against the parasite may be helpful as may biopsy.

Prevention of cystic disease is by treating dogs that may carry the disease and vaccination of sheep. Treatment is often difficult. The cystic disease may be drained through the skin, followed by medication. Sometimes this type of disease is just watched. The alveolar form often requires surgical intervention, followed by medications. The medication used is albendazole, which may be needed for years. The alveolar disease may result in death.

The disease occurs in most areas of the world and currently affects about one million people. In some areas of South America, Africa, and Asia, up to 10% of the certain populations are affected. In 2015, the cystic form caused about 1,200 deaths; down from 2000 in 1990. The economic cost of the disease is estimated to be around US$3 billion a year. It is classified as a neglected tropical disease (NTD) and belongs to the group of diseases known as helminthiases (worm infections). It can affect other animals such as pigs, cows and horses.

Terminology used in this field is crucial, since echinococcosis requires the involvement of specialists from nearly all disciplines. In 2020, an international effort of scientists, from 16 countries, led to a detailed consensus on terms to be used or rejected for the genetics, epidemiology, biology, immunology, and clinical aspects of echinococcosis.