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Trichinosis, also called trichinellosis, occurs when people consume raw or undercooked pork and wild game products infected with the larvae of a species of worm called Trichinella. Once inside the host, stomach acid breaks down the cyst surrounding the larvae and worms are released into the stomach. These worms pass into the small intestine, where they mature. After mating, a mature adult female lays eggs. These eggs develop into immature worms which penetrate the walls of the small intestine and travel to muscles through the arteries. Once in the muscles, the worms curl into balls and become enclosed in a capsule (encyst). The cycle is completed when another host consumes the meat of the affected muscles and becomes infected.

Trichinosis was once very common in the United States but infection is now rare. The number of cases has decreased because of legislation prohibiting the feeding of raw-meat garbage to hogs, commercial and home freezing of pork, and the public awareness of the danger of eating raw or undercooked pork products. Cases are now less commonly associated with pork products and more often associated with eating raw or undercooked wild game meats.


The first symptoms of trichinosis typically appear within a week after infection. Early symptoms include the following:

  • Abdominal discomfort
  • Nausea
  • Vomiting
  • Diarrhea

Later symptoms usually appear between two to eight weeks after exposure and include the following:

  • Muscle soreness
  • Fever
  • Swelling of the upper eye lid
  • Rash
  • Eye pain
  • Sensitivity to light
  • Sweats
  • Chills

Symptoms may range from mild to severe and depend on the number of infectious worms that were consumed. Asymptomatic infections may last for years.


Trichinosis is caused by the consumption of raw or undercooked meats containing encysted larvae of a species of Trichinella worm. The following meats are especially prone to carry Trichinella larvae:

  • Pork
  • Bear
  • Wild feline (such as a cougar)
  • Fox
  • Dog
  • Wolf
  • Horse
  • Seal
  • Walrus

This disease is not spread from person to person.

Risk Factors

People who consume raw or undercooked meats, particularly wild game meats, are at risk for developing trichinosis.


The following precautions should be observed to help prevent trichinosis infection:

  • Cook meat products until the juices run clear, or to an internal temperature of 170 degrees F.
  • Freeze pork less than six inches thick for 20 days at 5 degrees F to kill any worms.
  • Cook wild game meat thoroughly. Freezing wild game meats, even for long periods of time, may not effectively kill all worms.
  • Cook all meat fed to pigs or other wild animals.
  • Do not allow hogs to eat uncooked carcasses of other animals, including rats, which may be infected.
  • Clean meat grinders thoroughly after preparing ground meats.

Curing (salting), drying, smoking, or microwaving meat does not consistently kill the worms.


There are several safe and effective prescription drugs available to treat trichinosis. If you suspect you may be infected, contact your health care provider immediately. Treatment should begin as soon as possible and be sure to tell your health care provider if you have eaten raw or undercooked meat.

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