Trichinellosis FAQs

Trichinellosis, also called trichinosis, is caused by eating raw or undercooked meat of animals infected with the larvae of a species of worm called Trichinella. Infection occurs commonly in certain wild carnivorous (meat-eating) animals such as bear or cougar, or omnivorous (meat and plant-eating) animals such as domestic pigs or wild boar.

The signs, symptoms, severity and duration of trichinellosis vary. Nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort are often the first symptoms of trichinellosis. Headaches, fevers, chills, cough, swelling of the face and eyes, aching joints and muscle pains, itchy skin, diarrhea, or constipation may follow the first symptoms. If the infection is heavy, patients may experience difficulty coordinating movements, and have heart and breathing problems. In severe cases, death can occur.

For mild to moderate infections, most symptoms subside within a few months. Fatigue, weakness, muscle pain, and diarrhea may last for months.

Abdominal symptoms can occur 1–2 days after infection. Further symptoms usually start 2–8 weeks after eating contaminated meat. Symptoms may range from very mild to severe and relate to the number of infectious worms consumed in meat. Often, mild cases of trichinellosis are never specifically diagnosed and are assumed to be the flu or other common illnesses.

When a human or animal eats meat that contains infective Trichinella larvae, the acid in the stomach dissolves the hard covering of the cyst around the larvae and releases the worms. The worms pass into the small intestine and, in 1–2 days, become mature. After mating, adult females lay eggs. Eggs develop into immature worms, travel through the arteries, and are transported to muscles. Within the muscles, the worms curl into a ball and encyst (become enclosed in a capsule). The life cycle repeats when meat containing these encysted worms is consumed by another human or animal.

If you eat raw or undercooked meats, particularly bear, pork, wild feline (such as a cougar), fox, dog, wolf, horse, seal, or walrus, you are at risk for trichinellosis.

No. Infection can only occur by eating raw or undercooked meat containing Trichinella worms.

See your health care provider who can order tests and treat symptoms of trichinellosis . If you have eaten raw or undercooked meat, you should tell your health care provider.

A blood test or muscle biopsy can show if you have trichinellosis.

Several safe and effective prescription drugs are available to treat trichinellosis. Treatment should begin as soon as possible and the decision to treat is based upon symptoms, exposure to raw or undercooked meat, and laboratory test results.

Trichinellosis used to be more common and was usually caused by ingestion of undercooked pork. However, infection is now relatively rare. During 2011–2015, 16 cases were reported per year on average. The number of cases decreased beginning in the mid-20th century 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 less commonly associated with pork products and more often associated with eating raw or undercooked wild game meats.

  • The best way to prevent trichinellosis is to cook meat to safe temperaturesexternal icon. A food thermometer should be used to measure the internal temperature of cooked meat. Do not sample meat until it is cooked.
  • Curing (salting), drying, smoking, or microwaving meat alone does not consistently kill infective worms; homemade jerky and sausage were the cause of many cases of trichinellosis reported to CDC in recent years.
  • Freeze pork less than 6 inches thick for 20 days at 5°F (-15°C) to kill any worms.
  • Freezing wild game meats, unlike freezing pork products, may not effectively kill all worms because some worm species that infect wild game animals are freeze-resistant.
  • Clean meat grinders thoroughly after each use.

 

To help prevent Trichinella infection in animal populations, do not allow pigs or wild animals to eat uncooked meat, scraps, or carcasses of any animals, including rats, which may be infected with Trichinella.

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Page last reviewed: November 15, 2019