Echinococcosis is a parasitic disease caused by an infection from tiny tapeworms of the genus Echinocococcus. Echinococcosis is classified as either Cystic echinococcosis or Alveolar echinococcosis.

Cystic echinocccosis (CE), also known as hydatid disease, is caused by an infection with Echinococcus granulosus, an ~2-7 millimeter long tapeworm found most commonly in dogs (definitive host), in addition to sheep, cattle, goats, and pigs (intermediate hosts). Although most infections in humans are asymptomatic, CE causes harmful, slowly enlarging cysts in the liver, lungs, and other organs that often grow unnoticed and neglected for years.

Alveolar echinococcosis (AE) disease is caused by an infection with the larval stage of Echinococcus multilocularis, an ~1-4 millimeter long tapeworm found in foxes, coyotes, and dogs (definitive hosts). Although cases of AE in animals in endemic areas are relatively common, human cases are rare. AE poses a much greater health threat to people than CE, causing parasitic tumors to form in the liver, lungs, brain, and other organs. If left untreated, AE can be fatal.

Image: L to R: Echinococcus granulosus adult, stained with carmine. Close-up of the scolex of E. granulosus. In this focal plane, one of the suckers is clearly visible, as is the ring of rostellar hooks. Credit: DPDx