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Trichinosis

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Reporting Obligations

Confirmed and suspected cases shall be reported to the local Health Unit.

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Epidemiology

Aetiologic Agent

Trichinosis is a foodborne parasitic infection caused by the intestinal roundworm (a nematode), Trichinella spp., whose larvae migrate to muscles and become encapsulated in muscle tissues. There are many species of Trichinella capable of causing infection in mammals but in Canada, the most common species causing human infection include Trichinella spiralis, Trichinella nativa, Trichinella murrelli and Trichinella genotype T6.

Clinical Presentation

Clinical illness in humans is highly variable and can range from inapparent infection to a fulminating, fatal disease, depending on the number of larvae ingested.

Gastrointestinal symptoms, which appear shortly after infection, include abdominal discomfort, nausea, vomiting, and diarrhea. As larvae migrate into tissues, fever, myalgia, periorbital edema, urticarial rash, eosinophilia, and conjunctival and subungual hemorrhages may develop.

Cardiac and neurological complications may develop and may be fatal if severe.

Modes of Transmission

Eating raw or undercooked meat of animals containing the Trichinella larvae, in particular pork, pork products and beef products.

Incubation Period

Systemic symptoms usually appear about 8–15 days after ingestion of infected meat; this varies from 5–45 days depending on the number of parasites involved. GI symptoms may appear within a few days.

Period of Communicability

Not transmitted person-to-person; animal hosts may remain infective for months and meat from these animals remains infective until the larvae are killed by freezing, sufficient cooking, or irradiation.

Risk Factors/Susceptibility

Consumption of game meat.

Consumption of undercooked meat products (pork, beef).

Susceptibility is universal; infection results in partial immunity.

Diagnosis and Laboratory Testing

Diagnosis is based on clinical presentation and epidemiological evidence and can be confirmed by blood tests and skeletal muscle biopsy. Skeletal muscle biopsy taken more than 10 days after infection (most often positive after the fourth or fifth week of infection) frequently provides conclusive evidence of infection. Serum antibody titres rarely become positive before the second week of illness; testing paired acute and convalescent serum specimens usually is diagnostic.

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Treatment and Case Management

Provide education about the illness and how to prevent spread.

Specific treatment is under the direction of the attending health care provider. Treatment mainly involves administration of anthelmintics such as pyrantel, albendazole, or mebendazole which are effective in the intestinal stage and muscle-stage trichinosis.

Albendazole is available through Health Canada’s Special Access Program (SAP).

Additional information is available at: Guidance for Industry and Practitioners – Special Access Programme for Drugs Guidance Document (2013, or as current).

Patient Information

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Additional Resources

Centers for Disease Control and Prevention. “Parasites -Trichinellosis.”

References

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