DefinitionEchinococcus is an infection caused by the Echinococcus granulosus or Echinococcus multilocularis worm.Alternative NamesHydatidosis; Hydatid disease, Hydatid cyst diseaseCauses, incidence, and risk factorsEchinococcus is common in:AfricaCentral AsiaSouthern South AmericaThe MediterraneanThe Middle EastIn the United States, the disease is very rare. However, it has been reported in California, Arizona, New Mexico, and Utah.Humans become infected when they swallow eggs in contaminated food. The infection is carried to the liver, where cysts form. Cysts can also form in the:BrainBonesKidneyLungsSkeletal musclesSpleenRisk factors include being exposed to:CattleDeerFeces of dogs, wolves, or coyotesPigsSheepSymptomsA liver cyst may produce no symptoms for 10 - 20 years until it is larg