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Echinococcus

Last updated Sept. 5, 2018

Approved by: Maulik P. Purohit MD, MPH

CDC/ Dr. L.L.A. Moore, Jr.

Echinococcus is a zoonotic (passed by animals), parasitic disease caused by Echinococcus granulosus or Echinococcus multilocularis worm, also commonly called the hydatid worm.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Alveolar Echinococcosis
  • Polycystic Echinococcosis
  • Unilocularhydatid Disease

What is Echinococcus? (Definition/Background Information)

  • Echinococcus is a zoonotic (passed by animals), parasitic disease caused by Echinococcus granulosus or Echinococcus multilocularis worm, also commonly called the hydatid worm
  • Echinococcus is typified by the formation of cysts in various organs of the body such as the liver, brain, bones, kidney, lungs, skeletal muscles, and spleen. This leads to signs and symptoms of upper abdominal pain, chest pain, and cough with sputum and blood
  • The treatment of Echinococcus is undertaken using anti-parasitic medications and sometimes, the condition may require surgical interventions. Generally, the infection has good prognosis with appropriate treatment

Echinococcus infection may be of 3 different types namely:

  • Cystic Echinococcosis caused by Echinococcus granulosus
  • Alveolar Echinococcosis caused by E. multilocularis
  • Polycystic Echinococcosis caused by E. vogeli and/or E. oligarthrus

Among these Cystic Echinococcosis and Alveolar Echinococcosis are prominent in humans.

Who gets Echinococcus? (Age and Sex Distribution)

Echinococcus is a disease that is mainly found in animals such as foxes, coyotes, dogs, and cats.  As far as humans are concerned, any individual has the potential to be infected by Echinococcus.

The infection is more commonly observed in the northern hemisphere, particularly in regions such as:

  • Africa
  • Central Asia
  • South of South America
  • The Mediterranean region
  • The Middle Eastern region

Note:

  • Primary areas where E. granulosus are found include North America, especially the sheep-raising regions of Utah, California, Arizona, and New Mexico
  • Areas where E. multilocularis are found include North America, especially in the north central region, from Eastern Montana to Central Ohio, Alaska, and Canada

What are the Risk Factors for Echinococcus? (Predisposing Factors)

Risk factors for Echinococcus infection include:

  • Individuals who may come in contact with either wild or domesticated infected animals such as trappers, hunters, or veterinarians
  • Other individuals who have close contact with wild foxes and coyotes (or their feces)
  • Household dogs and cats that are exposed to, or eat the infected animals
  • Individuals who eat (or touch) uncooked meat that is infected
  • People involved in raising sheep as their occupation

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Echinococcus? (Etiology)

  • Echinococcus is a disease that is spread from infected animals, caused mostly by the parasitic worm Echinococcus granulosus or Echinococcus multilocularis
  • This worm is also known as the hydatid worm, hyper tape worm or dog tapeworm; members of cyclophyllidean tapeworms, belonging to the family of Taeniidae (or flatworms). Hydatid Cyst Infection is another term that describes Echinococcus infection

Echinococcis is transmitted to humans by the following causes:

  • The accidental consumption of food, water, or even soil contaminated by the fecal matter of an infected animal (usually a dog)
  • Close contact with an infected animal by way of handling (treating), petting, and playing, because eggs released in an infected animal’s stool, may eventually ends up in its fur

What are the Signs and Symptoms of Echinococcus?

The common signs and symptoms exhibited by Echinococcus are:

  • Upper abdominal pain
  • Cyst formation in the liver, brain, bones, muscles, kidney, lungs, or spleen
  • Palpable masses in the affected organs
  • Chest pain, cough, and bloody sputum
  • Fever
  • Severe skin itching
  • Headache, nausea

How is Echinococcus Diagnosed?

The diagnosis of Echinococcus infection may include:

  • Complete evaluation of the individual’s medical history (including collection of information about their occupation, recent travel history, etc.) along with a thorough physical exam. The physical examination may reveal:
    • Abdominal pain or tenderness
    • Skin excoriation due to itching             

Other diagnostic tests may include:

  • Stool test for detecting the presence of the parasites
  • Ultrasound scan of the abdomen
  • Abdominal CT scan
  • Abdominal and chest x-ray
  • Thoracic CT scan or ultrasound scan
  • Liver function tests
  • Blood tests are performed to examine for the presence of antibodies against worms and parasites

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Echinococcus?

The hydatid cyst can rupture and cause serious illness such as:

  • High-grade fever
  • Low blood pressure
  • Shock with multi-organ failure
  • There is all likelihood of the cyst spreading to other parts of the body

Complications that can arise when the bile ducts or hepatic vessels are blocked include:

  • Obstructive jaundice: Blockage of bile flow out of the liver
  • Cholangitis: Infection in the bile duct
  • Portal vein thrombosis: Clotting of blood in the large vein, called hepatic portal vein, which carries blood from the digestive organs and spleen to the liver
  • Portal hypertension: High blood pressure in the portal vein and its tributaries, resulting in bleeding of the submucosal veins in the lower third of the esophagus (the food pipe)
  • Budd-Chiari disease or hepatic vein obstruction: Blockage of the hepatic vein that carries blood away from the liver

Complications that can arise when the infection spreads to other parts of the body include:

  • Adrenal gland or kidney dysfunction
  • Small bowel obstruction
  • Gastric or intestinal perforation: A serious condition in which there is a penetration (perforation) of the wall of the stomach or small intestine (small bowel), which results in  the intestinal contents flowing into the abdominal cavity
  • Skin tumor-like lesions
  • Tumor-like bone lesions and fracture
  • Right atrium parasitic thrombus: A clot that travels from the venous system to the lung
  • Pulmonary embolism: Formation of clot in the lung blood vessels or one that has travelled to the lung from elsewhere

Focal cerebral disorders such as:

  • Seizures (shaking of the body)
  • Hemiparesis (weakness of one side of the body)
  • Aphasia (Impairment of language ability)

How is Echinococcus Treated?

The treatment of Echinococcus may be generally prolonged and complicated. It may include:

  • Treatment with albendazole and mebendazole drugs, which are prescribed for a period of 3 months
  • Praziquantel drug may also be prescribed in combination with albendazole and mebendazole
  • In some cases, the cyst needs to be removed through extensive surgery that can be complicated

How can Echinococcus be Prevented?

Following are the preventive measures and strategies to control the spread of Echinococcus infection:

  • Health education and awareness of Echinococcus should be spread among the local people
  • Routine removal of tapeworms from dogs help in reducing the risk
  • Avoid touching dead or live animals without wearing gloves
  • Keeping wild animals as pets should be discouraged
  • Proper hand washing with soap and clean water after handling pets or other animals
  • Fruits and vegetables should not be directly picked from the ground (or after purchase from the markets) and eaten. It should be washed thoroughly before being consumed
  • Avoid feeding sheep viscera (organs) to dogs
  • If pet dogs are known to have eaten rodents, consult the veterinarian at once
  • Home slaughtering of sheep and other livestock should be restricted or strictly controlled
  • The importance of washing hands to prevent infection and infection spread must be taught to children

What is the Prognosis of Echinococcus? (Outcomes/Resolutions)

  • Generally, Echinococcus infection has good prognosis with appropriate treatment
  • Older adults have a poorer prognosis, as compared to the younger children or adults

Additional and Relevant Useful Information for Echinococcus:

According to a World Health Organization (2015) report, over a million people are affected by Echinococcus on any given day.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: May 17, 2015
Last updated: Sept. 5, 2018