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Echinococcus is an infection caused by the Echinococcus granulosus or Echinococcus multilocularis worm.

Alternative Names

Hydatidosis; Hydatid disease, Hydatid cyst disease


Echinococcus is common in southern South America, the Mediterranean, the Middle East, central Asia, and Africa. In the United States, the disease is very rare, but 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 lungs, as well as in the brain, bones, skeletal muscles, kidney, spleen, and other tissues. A liver cyst may produce no symptoms for 10 to 20 years until it is large enough to be felt by physical examination or to produce symptoms.

Risk factors include exposure to cattle, sheep, pigs, or deer or exposure to the feces of dogs, wolves, or coyotes.


  • abdominal pain in upper right quadrant
  • severe itching of skin
  • cough
  • bloody sputum
  • chest pain
  • fever

Exams and Tests

A physical examination may reveal abdominal pain, involvement of other organs, skin signs, and occasionally, shock.

The following tests may be done to determine the presence and location of the cysts:

  • Chest x-ray
  • Thoracic CT scan or ultrasound
  • Abdominal X-ray
  • Abdominal CT scan or ultrasound
  • Blood test for antibodies to echinococcus
  • Liver function tests

Most often, echinococcosis does not cause symptoms and is found accidentally when an imaging test is done for another reason.


Many patients can be successfully treated with albendazole or mebendazole, which must often be used in long courses of up to three months. Another drug, praziquantel, may be helpful in combination with albendazole or mebendazole.

If the cysts are in troublesome locations, the definitive treatment is to remove them surgically if the patient's condition permits the procedure. This can be a complicated type of surgery.

Outlook (Prognosis)

The probable outcome is good for people with cysts that respond to oral medication treatment.

Possible Complications

The cysts may rupture and cause severe illness, including fever, low blood pressure, and shock. In such cases, the cysts may also disperse and cause widespread disease throughout the body.

When to Contact a Medical Professional

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


In areas where the disease is known to occur, health education and routine deworming of dogs to remove tapeworms help prevent the disease.

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