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.
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
- Bacterial 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 Laboratory Tests
Screen for Trichinella exposure
Test is not diagnostic and must be correlated with supporting patient history and pathologic findings
Qualitative Enzyme-Linked Immunosorbent Assay
Assess for presence of eosinophilia, suggesting parasitic infection
Automated Cell Count/Differential
Nonspecific indicator of muscle inflammation or damage
Quantitative Enzymatic
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
Quantitative Enzymatic
Medical Experts
Couturier

References
16881396
18625683
21881948
El-Beshbishi SN, Ahmed NN, Mostafa SH, et al. Parasitic infections and myositis. Parasitol Res. 2012;110(1):1-18.
15071823
Gamble HR, Pozio E, Bruschi F, et al. 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.
19136437
18050431
Mitreva M, Jasmer DP. Biology and genome of Trichinella spiralis. WormBook. 2006;1-21.