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Echinococcus Multilocularis Infection

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Reporting Obligations

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Epidemiology

Aetiologic Agent

Echinococcus multilocularis infection in humans is caused by the ingestion of eggs of the E. multilocularis tapeworm. Once ingested, the eggs develop into the larval form, which grows as multiple, small budding cysts.

Clinical Presentation

Proliferation of the larval stage of E. multilocularis produces a highly invasive, destructive disease called alveolar echinococcosis. Once clinical signs of alveolar echinococcus develop, lesions are usually found in the liver and expand to produce solid, tumour-like masses. Metastases can result in secondary cysts and larval growth in other organs. Clinical manifestations depend on the size and location of cysts, but are often confused with hepatic carcinoma and cirrhosis.

Modes of Transmission

Ingestion of eggs passed in the feces of foxes, coyotes, dogs or cats that have fed on infected rodents. Fecally soiled dog hair and other environmental fomites also serve as vehicles of infection.

Incubation Period

Infection of humans with E. multilocularis is characterized by an initial asymptomatic incubation period of 5–15 years.

Period of Communicability

E. multilocularis eggs are highly resistant, and may remain infective for approximately one year in a suitable, moist environment at lower temperatures. There is no person to person transmission.

Risk Factors/Susceptibility

Susceptibility is general. Due to the long incubation period, alveolar echinococcosis usually affects adults.

Diagnosis and Laboratory Testing

Diagnosis is complex and based on serodiagnosis for early stages of infection, and histopathology for later stages of infection, when lesions have become apparent in the liver or other organs.

Serologic testing for E. multilocularis is not performed in Canada. Rather, serum specimens with a requisition for “alveolar hydatid” or “E. multilocularis” are sent for reference laboratory testing in Switzerland, after approval of the request by the PHO Laboratory.

Search Echinococcus on Testing Information Index page.

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Treatment and Case Management

Treatment is under the direction of the attending health care provider. All patients require treatment. Provide cases with information about the infection and how it is transmitted as listed below.

Education of both pet owners and individuals in high risk occupations (veterinary staff, wildlife workers, hunters and trappers, etc.) about the lifecycle of the parasite and risks of exposure to E. multilocularis eggs is an important preventive measure.

Hunters and trappers handling foxes, coyotes or other wild canids should wear plastic gloves when handling these animals or their carcasses.

Wild fruits and vegetables should not be collected from the ground or eaten. All wild-picked foods should be washed carefully or cooked before being eaten.

All dogs and cats having access to wild rodents in areas known to be endemic for E. multilocularis should be dewormed monthly with praziquantel to reduce the risk of exposure to parasite eggs in household environments. Pet owners should prevent dogs and cats from eating rodents.

Regular, frequent hand hygiene after handling pets and their feces, and before handling food, can reduce the risk of transmission to humans. Areas inhabited by dogs and cats with known E. multilocularis infections should be decontaminated to prevent risk of exposure to parasitic eggs on surfaces such as pet beds, floors, carpets and car interiors.

Patient Information

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Additional Resources

Centers for Disease Control and Prevention. “Echinococcus”, December 2012.

References

Ministry of Health and Long-Term Care, Infectious Diseases Protocol, May 2019.