Trichinosis

Trichinosis (trih-kih-NO-sis) is a parasitic infection that comes from eating raw or undercooked meat. It is caused by species of the roundworm Trichinella (trih-kih-NEH-luh).

What Is Trichinosis?

Also called trichinellosis (trih-kih-neh-LO-sis), trichinosis can occur when people eat meat that is infected with the larvae * of Trichinella roundworms (also called nematodes, NEE-muh-todes); Trichinella spiralis (spy-RAL-is) is the most common species that causes trichinosis. People can only become infected by eating infected meat; the disease is not spread through human contact. The parasite can also spread when animals eat the infected flesh of other animals. Most often, meat infected with the parasite comes from pigs or wild game, such as bear, horse, wolf, and fox.

Trichinella larvae form cysts * in meat. When an animal eats this meat, the animal's stomach acid dissolves the cysts, and the worms are released into the body. They travel to the small intestine * , where they grow into adult worms and mate. After about a week, the mature female worm releases larvae, which travel through the bloodstream to the muscles. There they form the hard cysts that began the cycle. The cysts remain in the muscles, and people become infected when they eat these cysts in animal meat.

How Common Is Trichinosis?

How Do People Know They Have Trichinosis?

The length of the period between eating the infected meat and the first symptoms of illness depends on the number of parasites in the meat and how much a person ate. The time before symptoms occur can range from 1 to 45 days, but symptoms often surface in 10 to 14 days. Symptoms can be mild and even go unnoticed, but they usually start with fever, diarrhea (dye-uh-REE-uh), stomach pain, nausea (NAW-zee-uh) and vomiting, and extreme tiredness. Other symptoms may follow, such as headache, cough, chills, muscle and joint pain, eye swelling, and constipation. If the infection is severe, a person may have trouble with coordination as well as heart and breathing problems.




The splinter hemorrhages under the fingernails of a patient with the parasitic disease trichinosis.





The splinter hemorrhages under the fingernails of a patient with the parasitic disease trichinosis. Trichinosis, or trichinellosis, is caused by eating raw or undercooked pork infected with the larvae of a species of worm called Trichinella. Initial symptoms include nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort.
CDC/Dr. Thomas F. Sellers/Emory University.

How Do Doctors Diagnose and Treat Trichinosis?

A blood test or muscle biopsy * can be done to determine whether a person has trichinosis. The blood test can detect antibodies * working to destroy the parasite, and the biopsy shows the presence of cysts in the muscles. Asking if a person has recently eaten game or traveled outside the United States may provide information useful in making the diagnosis.

The infection can be treated with various medications to kill the worms in the intestine, but the medication does not get rid of the larvae that have produced cysts in the muscles. These larvae remain in a dormant (inactive) state in the muscle tissue. If the infection is mild, symptoms usually go away after a few months. Muscle aches and weakness may last longer. Some people require only bed rest; others need to be hospitalized and receive oxygen and intravenous (in-tra-VEE-nus) fluids (fluids injected directly into a vein). Severe complications of trichinosis include inflammation of the heart muscle, heart failure, lung problems, delirium * , and coma * . The disease can be fatal if it is not treated.

How Can Trichinosis Be Prevented?

The best way to prevent infection is to eat only thoroughly cooked meat. Curing, drying, salting, and microwaving meat may not kill Trichinella larvae. Wild game are the meats of greatest concern, including bear, wild pigs or boar, wild feline (such as a cougar), fox, wolf, horse, seal, or walrus. Meat is thoroughly cooked when the juices are clear (not bloody), and the meat has reached an internal temperature of between 145°F and 165°F, depending on the cut of meat and type of animal. Freezing meat at subzero temperatures for several weeks also should kill any larvae in cysts. Raw meat can contaminate work surfaces, so it must not touch surfaces used to prepare food, and grinders and other utensils used with raw meat must be cleaned thoroughly and not used to prepare cooked meat.

See also Intestinal Parasites • Parasitic Diseases: Overview • Roundworm Infection • Zoonoses: Overview

Resources

Books and Articles

Smith, Darvin Scott. “Trichinosis.” Medscape, April 16, 2013. http://emedicine.medscape.com/article/230490-overview (accessed November 18, 2015).

Websites

Boston Public Health Commission. “Trichinosis.” (accessed November 18, 2015).

MedlinePlus. “Trichinosis.” U.S. National Library of Medicine. https://www.nlm.nih.gov/medlineplus/ency/article/000631.htm (accessed November 18, 2015).

Organizations

Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 888-674-6854. Website: http://www.cdc.gov (accessed November 18, 2015).

U.S. Department of Agriculture. 1400 Independence Ave. SW, Washington, DC 20250. Telephone: 202-720-2791. Website: http://www.usda.gov (accessed November 18, 2015).

* larvae (LAR-vee) are the immature forms of an insect or worm that hatches from an egg.

* cysts (SISTS) are shell-like enclosures that contain small organisms in a resting stage.

* small intestine is the part of the intestines—the system of muscular tubes that food passes through during digestion—that directly receives the food when it passes through the stomach.

* biopsy (BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.

* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

* delirium (dih-LEER-e-um) is a condition in which a person is confused, is unable to think clearly, and has a reduced level of consciousness.

* coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened, and cannot move, see, speak, or hear.

  This information is not a tool for self-diagnosis or a substitute for professional care.