Cystic echinococcosis is mostly found in South and Central America, Africa, the Middle East, China, Italy, Spain, Greece, Russia, and the western United States (Arizona, New Mexico, and California).

Sheep, goats, cattle, camels, pigs, wild herbivores, and rodents are the usual intermediate hosts, but humans can also be infected.

From the inner lining of its wall, protoscoleces (i.e. scoleces with invaginated tissue layers) bud and protrude into the fluid filling the cyst.

In their small intestines, protoscoleces turn inside out, attach, and give rise to adult tapeworms, completing the lifecycle.

They are regularly found in the liver (and every possible organ: spleen, kidney, bone, brain, tongue and skin) and are asymptomatic until their growing size produces symptoms or are accidentally discovered.

The origin of these parasites based on host-parasite co-evolution comparisons was North America or Asia, depending on whether the ancestral definitive hosts were canids or felids.

The genus Echinococcus evolved in North America in canids and began to diversify 5.8 million years ago.

In 2020, an international effort of scientists from 16 countries lead to a detailed consensus on terminology, i.e. the terms to be used or rejected for the genetics, epidemiology, biology, immunology and clinical aspects linked with Echinococcus species.