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Trichinosis

What is it?

Trichinosis is a parasitic disease often spread through raw or undercooked meat, especially pork.Most cases are mild and cause few if any symptoms. Trichinosis is transmitted to humans who ingest the larvae of a parasitic roundworm found in the muscles of infected animals. These larvae mature into adult worms in the lining of the intestine. The fertilized female can produce thousands of larvae that may leave the intestine to migrate throughout the body and form cysts in the muscles of the host. These cysts can persist indefinitely. If symptoms do occur, those resulting from infestation of the intestine may begin within one to two days to about a week after eating the infected meat. Symptoms due to muscle involvement typically begin a week later and subside gradually after a few weeks, but they sometimes last for several months. Severity depends on the number of larvae consumed and the condition of the host's immune system. In many people, trichinosis resolves on its own; however, treatment is necessary if larval cysts in the muscles of the host produce significant muscle inflammation. Rarely, the infection may cause serious, even fatal, complications involving the heart, lungs, or central nervous system. The incidence of trichinosis in the United States has dropped greatly over the past few decades thanks to public health regulations, but it is still important to cook all meat thoroughly, particularly pork and pork products, as well as wild game (such as bear, deer, and boar).

What Causes It?

  • Trichinosis is caused by the roundworm Trichinella spiralis, which lives in the intestines and muscles of many species of animals. The disease is transmitted to humans by ingestion of undercooked meat from such animals. Larvae released by intestinal worms enter the bloodstream and muscles where they form cysts that can induce an inflammatory response and lead to damage to the heart, lungs, and brain.

Prevention

  • Cook pork and other meat thoroughly. Pork should be cooked until all pink portions turn white or gray.
  • As an alternative precaution, store meat for at least three weeks in a deep freezer before cooking it.

Diagnosis

  • Patient history (including recent food consumption history) is taken. Physical examination may reveal characteristic signs of trichinosis infection.
  • Blood tests will reveal an elevated eosinophil count and antibodies against T. spiralis.
  • Stool analysis may detect worms and larvae.
  • The most definitive test is a muscle biopsy to detect the presence of the T. spiralis larvae.
  • If possible, a portion of the suspect meat is analyzed.

How to Treat It

  • In mild cases treatment may not be necessary.
  • Mebendazole may be prescribed to kill the worms and so relieve symptoms.Mebendazole kills larvae as well as adult worms, but safety in children under two or pregnant women has not been established.
  • Acetaminophen or aspirin may be used to reduce fever and ease discomfort.
  • When the heart is affected, bed rest is necessary until symptoms subside.
  • Corticosteroid drugs may be prescribed to reduce inflammation in severe cases, or for patients who have an allergic response to the parasite.

When to Call a Doctor

  • If you experience the symptoms of trichinosis, especially if you have eaten pork or wild game recently, see a doctor as soon as possible.