Trichinella species
MICROBIOLOGY
- Trichinosis occurs with ingesting undercooked meat contaminated with infective larvae of Trichinella spp.
- Seven species of roundworms from the genus Trichinella cause human disease:
- T. spiralis (most common) is found worldwide in various carnivorous and omnivorous hosts.
- T. nativa is found in arctic regions (bears, foxes, walruses).
- T. nelsoni is found in sub-Saharan Africa (felines, hyenas, bush pigs).
- T. britovi is found in Europe, Asia, and Africa (various carnivores).
- T. pseudospiralis is found worldwide (in wild mammals and birds).
- T. murelli is found in the United States and Japan (wild mammals).
- T. papuae is found in Papua New Guinea and Southeast Asia (domestic and feral pigs, saltwater crocodiles, and turtles).
- T. zimbabwensis in Tanzania (crocodiles) and T. patagoniensis in South America (cougars) are not known to cause human disease.
- Seven species of roundworms from the genus Trichinella cause human disease:
- Epidemiology: worldwide.
- From 1986-2009, there were 65,818 reported cases across 41 countries (with 42 deaths).
- Now an estimated 10,000 cases/year globally.
- In the U.S., ~16 cases/years were reported (2011-2016).
- Decreased cases ascribed to improved pig-raising practices in the pork industry, commercial and home freezing of pork, and public awareness of the danger of eating raw or undercooked meat products.
- Cases associated with raw or undercooked wild game meats have remained relatively constant.
- From 1986-2009, there were 65,818 reported cases across 41 countries (with 42 deaths).
- Life cycle:
- Undercooked meat containing encysted larvae is eaten.
- Larvae are released from the cysts with exposure to gastric acid and pepsin.
- Larvae invade the small bowel mucosa, where they mature into adults.
- Adult females release larvae that migrate to striated muscle where they encyst and may remain infective for years.
- Adult worms are 1.5 x 0.05mm (male) and 3.5 x 0.06mm (female).
- Carnivorous animals keep the life cycle going by feeding on infected rodents or meat from other animals.
- Common hosts:
- Pigs are the most common source of human infection worldwide, but most U.S. swine are fed grains and are, therefore, uninfected.
- Bears are the most common source in the U.S.
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Last updated: May 6, 2023
Citation
Crowell, Trevor A. "Trichinella Species." Johns Hopkins ABX Guide, The Johns Hopkins University, 2023. Pediatrics Central, peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540561/all/Trichinella_species.
Crowell TA. Trichinella species. Johns Hopkins ABX Guide. The Johns Hopkins University; 2023. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540561/all/Trichinella_species. Accessed October 6, 2024.
Crowell, T. A. (2023). Trichinella species. In Johns Hopkins ABX Guide. The Johns Hopkins University. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540561/all/Trichinella_species
Crowell TA. Trichinella Species [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2023. [cited 2024 October 06]. Available from: https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540561/all/Trichinella_species.
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