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
Conjunctival hemorrhage and fever
Myalgia and eosinophilia
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
Screen for Trichinella exposure
Test is not diagnostic and must be correlated with supporting patient history and pathologic findings
Assess for presence of eosinophilia, suggesting parasitic infection
Nonspecific indicator of muscle inflammation or damage
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
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
Related Topics Last Update: October 2019
