Trichinella

Trichinellosis is a foodborne parasitic disease caused by the nematode,Trichinella spiralis.  Human infection occurs following consumption of raw or undercooked meat infected with viable Trichinella larvae. In recent years, proportionally fewer cases have been associated with consumption of commercial pork products in the United States and more with meat from wild game such as bear, seal and walrus. The decline in the number of cases is most likely attributed to USDA efforts to educate consumers to fully cook fresh pork to temperatures high enough to inactivate Trichinella (160°F or 71°C).

Trichinella infection in human hosts can be divided into an intestinal (enteral) phase and a muscular (parenteral) phase. After ingestion, larvae are released into the intestinal mucosa and then migrate to blood vessels, from which they spread throughout the body before reaching the skeletal muscles. During the enteral phase, infection with low intensity (<70 larvae) can remain asymptomatic, but infection with approximately 70–150 or more larvae can cause gastroenteritis with diarrhea, abdominal pain and vomiting approximately 2 days after infection. The parenteral phase is characterized by fever, myalgia, periorbital edema, eosinophilia, and increased levels of muscle enzymes such as creatine kinase. Systemic signs and symptoms typically occur 1 to 2 weeks after ingestion and last for 1 to 8 weeks. Death is usually attributed to myocarditis, meningoencephalitis, or pneumonitis. Respiratory failure can be caused by parasitism of respiratory muscles.

Diagnosis of trichinellosis requires serologic testing for Trichinella-spiralis antibody by enzyme immunoassay or a Trichinella-positive muscle biopsy specimen in a patient with clinical signs or symptoms compatible with trichinellosis. Antibodies to Trichinella spiralis may not be detectable until 3 weeks after the onset of infection. Both serologic testing and biopsy have limited sensitivity in early infections. Antibody to Trichinella can persist for years.  Positive Trichinella antibody may represent previous infection and may be misinterpreted as the cause of current illness in a patient exhibiting trichinellosis-like signs or symptoms.

Specimen requirement for Trichinella antibody is a red top tube of blood. 

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