Trichinella spiralis - Trichinellosis

Trichinosis is a zoonotic disease transmitted by eating uncooked or undercooked infected meat products (mainly pork). Trichinella infections are most often diagnosed in the laboratory based on detection of antibodies to excretory/secretory Trichinella antigen by ELISA or IFA. Testing is rarely positive in early disease. IgG antibodies can be detected approximately 12 to 60 days postinfection.

Tabs Content

Clinical Overview

Diagnosis

Indications for Testing

Abdominal pain, nausea, and diarrhea, followed by fever, weakness, and muscle pain
Ingestion of improperly prepared meat (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 enzyme-linked immunosorbent assay (ELISA) or indirect fluorescent antibody (IFA)
- Detectable 2-4 weeks after infection (may be >1,000/mL)
- Cross reacts with other parasitic infections
- Rarely positive in early disease

Histology

Larvae detection possible through biopsy and pathologist examination

Imaging Studies

Not indicated for diagnosis
May demonstrate calcified cysts on plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI) – “puffed rice” or “spindle shaped” appearance

Differential Diagnosis

Protracted diarrhea
- Bacterial diarrhea
  - Salmonella typhi (typhoid fever)
  - Shigella spp
- Viral diarrhea
- Parasitic diarrhea
Periorbital/facial edema and fever
- Glomerulonephritis
- Serum sickness
- Polymyositis
- Dermatomyositis
- Polyarteritis nodosa
Conjunctival hemorrhage and fever
- Leptospirosis spp
- Endocarditis
Myalgia and eosinophilia
- Eosinophilic fasciitis
- Eosinophilia-myalgia syndromes (toxic oil, tryptophan)
Muscle weakness/pain
- Polymyositis
- Myopathic disease

Background

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
- 2 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 number of larvae present
- Myocarditis, encephalitis, and pneumonia account for most deaths

Prevention

Fully cook potentially infected meat
Freeze potentially infected meat at -15°C for 3 weeks

ARUP Lab Tests

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.

Trichinella Antibody, IgG 3000005
Method: Qualitative Enzyme-Linked Immunosorbent Assay

Recommended Use

Screen for Trichinella exposure

Test is not diagnostic and must be correlated with supporting patient history and pathologic findings

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

Recommended Use

Assess for presence of eosinophilia, suggesting parasitic infection

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

Recommended Use

Nonspecific indicator of muscle inflammation or damage

Aldolase, Serum 0020012
Method: Quantitative Enzymatic

Recommended Use

Do not use as a stand-alone test

This nonspecific test has been replaced by other enzyme tests such as creatine kinase (CK), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) as more specific markers of muscle or liver damage

Medical Experts

Couturier, Marc Roger, PhD, D(ABMM), Medical Director, Microbial Immunology, Parasitology and Fecal Testing, and Infectious Disease Antigen Testing at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

References

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

Last Update: March 2018

Trichinella spiralis - Trichinellosis

Diagnosis

Indications for Testing

Laboratory Testing

Histology

Imaging Studies

Differential Diagnosis

Background

Epidemiology

Organism

Clinical Presentation

Prevention

ARUP Lab Tests

Medical Experts

References

Guidelines

General References

ARUP Laboratories

ARUP Websites

ARUP Consult


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