Trichinellosis Cook Thoroughly Do Not Feed To Pets Transmissable To Humans
 
Causative Agent
  • Parasitic and zoonotic disease of carnivorous mammals and birds caused by infection with the roundworm, Trichinella spiralis.
Images
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Trichinella Life Cycle Trchinella - Muscle
Life cycle of Trichinella. Bear muscle showing the encysted larvae at 200x magnification.
Distribution
Geographic:
  • Worldwide, except for Australia and Antarctica.
Seasonality:
  • Throughout the year.
Hosts, Transmission and Life Cycle
Hosts:
  • Primarily a disease of carnivores with scavenging or cannibalistic tendencies.
  • Several wildlife species in North America are known to be affected, including bears (Ursidae), wild dogs and cats, pigs (Suidae), seals (Phocidae, Otariidae), walruses (Odobenus rosmarus), rodents and mustelids.
  • Humans can become infected by T. spiralis by consuming undercooked, infected meat.
Generalized Life Cycle:
  • Refer to the above generalized life cycle diagram of Trichinella sp.
  • Transmission between hosts occurs when infected meat is consumed.
  • Cysts containing larvae are digested; larvae form cysts in the inner surface of the small intestine where they mature into adults and mate.
  • New larvae move via the bloodstream to muscle where they remain as the infective stage until eaten by a susceptible carnivore or scavenger.
  • Cysts may remain in muscle for 6-12 months and can survive after the death of the host, and so infect scavengers.
Signs and Symptoms
  • Like other adult roundworms, T. spiralis are unsegmented, cylindrical and tapered at both ends, and can measure between 1.2 - 2.2 cm in length.
  • In wildlife, disease can occur at two stages of infection: in the muscle and in the intestines
    • muscle: muscle pain, edema, fever; large burdens of cysts may lead to death;
    • intestines: adult worms may cause hemorrhage.
  • In humans, symptoms such as edema around the eyes, muscle pain, fever, diarrhea, itchiness in the skin, and lesions of the skin have been described.
  • More serious cases in humans have caused inflammation of the brain, heart failure, and breathing difficulties as a result of an infected diaphragm.
Meat Edible?
  • Humans may contract T. spiralis from eating improperly cooked meat of an infected animal.
  • Meat from an infected animal should not be fed to dogs or cats.
Human Health Concerns and Risk Reduction
  • Trichinella is a potential zoonotic parasite.
  • Infection can be spread to humans through consumption of improperly cooked meat, especially from bears and seals.
  • To minimize the chances of infection, meat must be cooked to 77ºC throughout to kill all larvae that may be present. Microwave ovens do not uniformly cook meat and, as a result, may not kill the parasite.
  • Freezing meat is NOT a reliable way of killing Trichinella roundworms.
  • Several safe and effective prescription drugs are available to treat trichinellosis. Treatment should begin as soon as possible and the decision to treat is based upon symptoms, exposure to raw or undercooked meat, and laboratory test results.
  • Trichinellosis is a reportable disease in Canada, and under the Health of Animals Act, all cases must be reported to the Canadian Food Inspection Agency (CFIA).
Samples for Diagnosis
  • Muscle tissue containing larval cysts should be submitted for diagnosis.
  • Cysts may be difficult to see with the naked eye; however, active muscles such as the tongue, diaphragm and muscles of the jaw usually contain the highest concentrations of infective larvae.
Further Reading
Return to Manual Home Page Disease List - Body Region Affected Disease List - Causative Agent or Risk Factor Disease Surveillance Form Glossary Contact Information
Return to Manual Home Page Return to Disease List - Body Region Affected Return to Disease List - Causative Agent or Risk Factor Disease Surveillance Form Download Glossary Contact Information