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Echinococcus is an infection caused by the Echinococcus granulosus or Echinococcus multilocularis tapeworm. The infection is also called hydatid disease.


Echinococcus is common in:

  • Africa
  • Central Asia
  • Southern South America
  • The Mediterranean
  • The Middle East

In the United States, the disease is very rare. But 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:

  • Brain
  • Bones
  • Kidney
  • Lungs
  • Skeletal muscles
  • Spleen

Risk factors include being exposed to:

  • Cattle
  • Deer
  • Feces of dogs, wolves, or coyotes
  • Pigs
  • Sheep


A liver cyst may produce no symptoms for 10 to 20 years, until it is large enough to be felt by physical examination.

Symptoms include:

Exams and Tests

A physical examination may show signs of:

  • Abdominal pain
  • Problems with the skin and other organs
  • Shock

The following tests may be done to find the cysts:

Most often, echinococcosis is found when an imaging test is done for another reason.


Many patients can be treated with anti-worm medicines.

The cysts may be removed with surgery, if possible. But this can be a complicated surgery.

Outlook (Prognosis)

If the cysts respond to oral medication, the likely outcome is good.

Possible Complications

The cysts may break open (rupture) and cause severe illness, including:

  • Fever
  • Low blood pressure
  • Shock

The cysts may also spread throughout the body.

When to Contact a Medical Professional

Call your health care provider if you develop symptoms of this disorder.


In areas where the disease is known to occur, health education and routinely removing tapeworms from dogs can help prevent the disease.

Alternative Names

Hydatidosis; Hydatid disease, Hydatid cyst disease


King CH, Fairley JK. Cestodes (tapeworms). In: Mandell GL, Bennett JE, Dolin R, eds.Principles and Practice of Infectious Diseases.

Update Date 8/30/2014

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