What is Echinococcus multilocularis?
- A parasitic infection caused by ingesting eggs of the Echinococcus multilocularis tapeworm.
- Once the eggs are inside the body, they develop into a larval form which grows as multiple masses (cysts) within the body.
- Once cysts begin to form in the body, the person develops a serious disease called alveolar echinococcosis.
- Cysts usually begin in the liver and develop into solid tumor-like masses. The parasite can later spread and cause growths in other organs like the spleen, lungs, and brain.
How is it spread?
- Eggs are passed in the stool of foxes, coyotes, wolves, dogs, or cats that have eaten infected rodents.
- Humans can ingest the eggs after eating or encountering things that are contaminated with the stool of these animals.
- Eggs can also be present on the fur of animals if the fur is soiled with stool.
When do symptoms start?
- Symptoms usually start five to fifteen years after someone has become infected.
What are the symptoms?
- During the early stages (five to fifteen years) there are usually no symptoms.
- If symptoms do occur, they may include tiredness, weight loss, abdominal discomfort, and weakness.
- In the later stages, symptoms may mimic those of liver cancer or cirrhosis and include abdominal swelling, malnutrition, yellowing of the skin or eyes (jaundice), and mental confusion.
- If left untreated, alveolar echinococcosis can lead to death.
How long is it contagious?
- In the environment, eggs of the parasite remain infective for approximately one year in lower temperatures and when in a wet environment.
- Humans cannot spread the parasite to other humans.
How is it treated?
- All individuals with the infection will need treatment.
- Treatment often involves a combination of surgery and chemotherapy.
How is it prevented?
- Anyone who handles wild dogs, or their carcasses, should wear plastic gloves and complete hand hygiene after glove removal.
- Wash all wild-picked fruits and vegetables carefully before cooking or eating.
- All dogs and cats that have access to wild rodents should be dewormed monthly.
- Pet owners should try to avoid allowing cats and dogs to eat wild rodents.
- Regular and frequent hand washing after handling pets and their stool, and before handling food.
- Areas where infected dogs/cats frequently visit should be cleaned and disinfected well and often (e.g. pet beds, floors, carpets, and car interiors).
Where can I get more information about Echinococcus multilocularis?
Contact the Communicable Disease Control (CDC) Program at 705-474-1400, or toll-free at 1-800-563-2808, ext. 5229 or email us at cdc@healthunit.ca.
References:
- Ministry of Health. (2022). Infectious Diseases Protocol, Appendix 1: Echinococcus multilocularis infection.
- Ministry of Health (2025). Management of Echinococcus Multilocularis Infections in Animals Guideline.
- World Health Organization (WHO). (2021). Echinococcosis.
- Centers for Disease Control and Prevention. (2020). Parasites - Echinococcosis.
Created: Feb. 2026, by CDC