Trichinella
Trichinosis is a foodborne parasitic disease caused by the nematode, Trichinella spiralis. Human infection occurs following consumption of raw or undercooked meat that contains viable Trichinella larvae. In recent years, proportionally fewer cases have been associated with consumption of commercial pork products in the United States. 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).
Consumption of wild game, such as bear or seal, or non-commercially raised swine are now the most common sources of infection in the United States. A disproportionate number of cases occur in people of Asian descent who ingest raw meat. Laab (or larb) is a traditional dish of northern Thailand and Laos that is often made with raw pork and has been associated with outbreaks of trichinosis. Among travelers, consumption of regional delicacies such as raw horse meat in France and Italy, wild boar in Southeast Asia, and dog meat in China and Korea has led to trichinosis.
Trichinella infection in human hosts is a biphasic illness that can be divided into an intestinal (enteral) phase and a muscular (parenteral) phase. . In the enteral phase, larvae invade small-intestine mucosa, mature into adult worms, and produce larvae. During this phase patients typically present with symptoms of nausea, vomiting, watery diarrhea, and abdominal pain. These symptoms can last up to 3 to 4 weeks. During the parenteral phase, larvae invade the lymphatic and blood vessels, from where they disseminate throughout the body before reaching the skeletal muscles. The parenteral phase usually begins 2 weeks after ingestion and can last up to 8 weeks because adult worms in the intestine. The parenteral phase is characterized by fever, myalgia, weakness, headache, periorbital edema, eosinophilia, and increased levels of muscle enzymes such as creatine kinase. 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.
Reference value is a negative result.
Specimen requirement for Trichinella antibody is a red top tube of blood.
