Trichinella spiralis

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Clinical presentation and risk factor of improper meat preparation (mainly pork)

Laboratory Testing

  • Trichinella diagnosis information (CDC)
  • Nonspecific testing
    • CBC – eosinophilia
    • Muscle enzymes (creatine kinase, aldolase) – elevated during muscle inflammation stage
  • Trichinella antibody testing by ELISA or IFA
    • Detectable 2-4 weeks after infection (may be >1,000/mL)
    • Cross reacts with other parasitic infections
    • Uncommonly, positive in early disease

Histology

  • Muscle biopsy with staining detects larvae

Imaging Studies

  • Not indicated for diagnosis
  • May demonstrate calcified cysts on plain radiographs, CT, MRI – “puffed rice” or “spindle shaped” appearance

Differential Diagnosis

Trichinosis is a zoonotic disease transmitted by eating uncooked or undercooked infected meat products (mainly pork).

Epidemiology

  • Incidence – very low in U.S.
  • Transmission – raw or undercooked meat from infected mammals
    • Domestic pig, black bear, dog, horse, walrus, wild boar

Organism

  • Pork worm or Trichinella spiralis (Trichinella species are among the smallest of the parasitic nematodes)
  • Transmission occurs when uncooked or undercooked infected meat is eaten 
    • Cyst dissolves, parasite matures and deposits larvae in deep mucosa
    • Larvae enter lymphatics and are carried throughout the body where they again encyst
    • Two phases – intestinal and systemic

Clinical Presentation

  • During intestinal phase, if parasite burden is high, patient may experience diarrhea and abdominal pain
  • Symptoms from larval migration generally appear the second week after infection
    • Periorbital and facial edema
    • Hemorrhages in retina, nail beds, subconjunctival surfaces
    • Inflammatory muscle changes with associated myalgias
      • Severity of symptoms are related to the number of larvae present
    • Myocarditis, encephalitis, and pneumonia account for most deaths

Treatment

  • Treatment unsuccessful in most patients
    • Glucocorticoids useful for severe myositis and myocarditis
  • Infected patients usually recover with bedrest

Prevention

  • Fully cooking potentially infected meat or freezing at -15°C for 3 weeks
Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Trichinella Antibody, IgG, by ELISA 0050787
Method: Qualitative Enzyme-Linked Immunosorbent Assay

Creatine Kinase, Total, Serum or Plasma 0020010
Method: Quantitative Enzymatic

Aldolase, Serum 0020012
Method: Quantitative Enzymatic

Guidelines

Gamble HR, Pozio E, Bruschi F, Nöckler K, Kapel CM, Gajadhar AA. International Commission on Trichinellosis: recommendations on the use of serological tests for the detection of Trichinella infection in animals and man. Parasite. 2004; 11(1): 3-13. PubMed

General References

Cancrini G. Human infections due to nematode helminths nowadays: epidemiology and diagnostic tools. Parassitologia. 2006; 48(1-2): 53-6. PubMed

Crum-Cianflone NF. Bacterial, fungal, parasitic, and viral myositis. Clin Microbiol Rev. 2008; 21(3): 473-94. PubMed

El-Beshbishi SN, Ahmed NN, Mostafa SH, El-Ganainy GA. Parasitic infections and myositis. Parasitol Res. 2012; 110(1): 1-18. PubMed

Gottstein B, Pozio E, Nöckler K. Epidemiology, diagnosis, treatment, and control of trichinellosis. Clin Microbiol Rev. 2009; 22(1): 127-45, Table of Contents. PubMed

Mitreva M, Jasmer DP. Biology and genome of Trichinella spiralis. WormBook. 2006; 1-21. PubMed

Medical Reviewers

Last Update: August 2016