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

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

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

Recommended Use

Assess for presence of eosinophilia, suggesting parasitic infection

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

Recommended Use

Aid in the diagnosis of trichinosis

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

Recommended Use

Nonspecific indicator of muscle inflammation

Aldolase, Serum 0020012
Method: Quantitative Enzymatic

Recommended Use

Do not use as a stand-alone test

Measures the concentration of aldolase enzyme in serum

This nonspecific test has been replaced by more specific markers for muscle or liver damage

Can be used along with creatine kinase (CK) testing to screen and monitor therapies for skeletal muscular diseases

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