Trichinosis (trik-ih-NO-sis), sometimes called trichinellosis, is a type of roundworm infection. Roundworms are parasites that use a host body to stay alive and reproduce. Trichinosis occurs primarily among meat-eating animals (carnivores), especially bears, foxes and walruses. Trichinosis infection is acquired by eating larvae in raw or undercooked meat.

When humans eat undercooked meat containing trichinella larvae, the larvae mature into adult worms in the intestine over several weeks. The adults then produce larvae that migrate through various tissues, including muscle. Trichinosis is most widespread in rural areas throughout the world.

Trichinosis can be treated with medication, though it's not always necessary. It's also easy to prevent.

Symptoms Causes Risk factors Complications Prevention

Abdominal symptoms can occur within two to seven days of infection. Other symptoms usually start one to eight weeks later. Severity of symptoms usually depends on the number of larvae consumed in the infected meat.

Possibly no signs or symptoms

Mild cases of trichinosis — those with only a small number of parasites in your body — may cause no recognizable symptoms. Symptoms can develop with moderate or heavy infestation, sometimes progressing as the parasite migrates through your body.

Initial signs and symptoms

You swallow trichinella larvae encased in a cyst. Your digestive juices dissolve the cyst, releasing the parasite into your body. The larvae then penetrate the intestine, where they mature into adult worms and mate. At this stage, you may experience:

  • Diarrhea
  • Abdominal cramps

Later signs and symptoms

About a week after infection, the adult female worms produce larvae that penetrate the intestinal wall, enter your bloodstream, and eventually burrow into muscle or other tissue. This tissue invasion can cause:

  • High fever
  • Muscle pain and tenderness
  • Swelling of the eyelids or face
  • Weakness
  • Headache
  • Sensitivity to light
  • Pink eye (conjunctivitis)

When to see a doctor

If you have a mild case of trichinosis with no symptoms, you may never need medical attention. If you notice gastrointestinal problems or muscle pain and swelling about a week after eating pork or wild-animal meat, talk to your doctor.

There is no effective treatment to eliminate trichinella once larvae invade tissue. At that point, treatment is for symptoms only until the parasites die on their own.

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