Also known as: Trichinellosis
Hospital: Report by IDSS, facsimile, mail, or phone
Infection preventionist: Report by IDSS, facsimile, mail, or phone
Lab: Report by IDSS, facsimile, mail, or phone
Physician: Report by facsimile, mail, or phone
Local Public Health Agency (LPHA): Report by IDSS, mail, facsimile, or phone. Follow-up required
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Trichinosis is caused by Trichinella spiralis, a parasitic intestinal roundworm. Multiple species of Trichinella are capable of causing infection in mammals, but T. spiralis is the most common cause of human infection.
B. Clinical Description
Trichinosis in humans can range from asymptomatic to fatal, depending on the infective dose. In the week following ingestion of infected meat, a patient may experience nausea, vomiting, diarrhea and abdominal discomfort, as the released larvae mature and attach to the intestinal mucosa. A sudden onset of muscle soreness and pain, fever, edema of the upper eyelid and urticarial rash, 2 - 8 weeks after ingestion, is characteristic of earlier infection, as larvae migrate into muscle tissue. Eye pain, photophobia, thirst, profuse sweating, chills, weakness and a rapid increase in eosinophil counts on blood exam may also occur. Recurring fever up to 104°F usually stops after 1 - 6 weeks. In the most severe infections, cardiac and neurologic complications, sometimes leading to death, may occur in the 3rd - 6th week.
Swine, dogs, cats, horses, rodents and many wild animals, such as bear, wolf, wild boar, fox and Arctic marine mammals, can serve as reservoirs for Trichinella.
D. Modes of Transmission
Transmission occurs by ingestion of raw or undercooked meats containing Trichinella cysts. Pork and pork products are the most likely source. Beef products, which may become inadvertently adulterated with raw pork during processing, may also be a source. As many as 30% of domestic cases of trichinosis are thought to correlate with ingestion of meat from wild game animals. There is no person-to-person spread of trichinosis.
E. Incubation period
Gastrointestinal symptoms may appear within a few days after infection; appearance of systemic symptoms ranges from 5 - 45 days. The usual incubation period is 8 - 15 days. If large numbers of cysts are ingested, symptoms may occur more rapidly.
F. Period of Communicability or Infectious Period
Trichinosis is not transmitted directly from person-to-person. Animal hosts may remain infective for months, and meat from these animals remains infective until the larvae are killed by sufficient cooking, freezing or irradiation.
Trichinosis occurs worldwide, and affects people of all ages. The incidence of disease is dependent on local customs regarding eating pork or undercooked meats. Over the past 40 years, few cases of trichinellosis have been reported in the United States, and the risk of trichinellosis from commercially raised and properly prepared pork is very low. However, eating undercooked wild game, particularly bear meat, puts one at risk for acquiring this disease.
H. Bioterrorism Potential
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Trichinosis can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
In an outbreak setting, at least one case must be laboratory confirmed. Associated cases should be reported as confirmed if the patient shared an epidemiologically implicated meal or ate an epidemiologically implicated meat product and has either a positive serologic test for trichinosis or a clinically compatible illness.
American Academy of Pediatrics. 2003 Red Book: Report of the Committee on Infectious Diseases, 26th Edition. Illinois, American Academy of Pediatrics, 2003.
CDC. Trichinosis website: www.cdc.gov/parasites/trichinellosis/health_professionals/index.html
Heymann, D.L., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
McAuley, J.B., Michelson, M.K., Schantz, P.M., Trichinosis Surveillance, United States, 1987–1990. MMWR. 1990; 40(SS-3): 35-42.