What is Trichinosis?

Trichinosis, also called trichinellosis (TRICK-a-NELL-o-sis), is caused by eating raw or undercooked pork and wild game products infected with the larvae of a species of worm called Trichinella. Infection occurs worldwide, but is most common in areas where raw or undercooked pork, such as ham or sausage, is eaten.

What are the symptoms of a trichinosis infection?

Nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort are the first symptoms of trichinosis. Headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, itchy skin, diarrhea, or constipation 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, and diarrhea may last for months.

How soon after infection will symptoms appear?

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 trichinosis are never specifically diagnosed and are assumed to be the flu or other common illnesses.

How does infection occur in humans and animals?

When a human or animal eats meat that contains infective Trichinella cysts, the acid in the stomach dissolves the hard covering of the cyst 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). Infection occurs when these encysted worms are consumed in meat.

Am I at risk for trichinosis?

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

Can I spread trichinosis to others?

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

What should I do if I think I have trichinosis?

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

How is trichinosis infection diagnosed?

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

How is trichinosis infection treated?

Several safe and effective prescription drugs are available to treat trichinosis. 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.

Is trichinosis common in the United States?

Infection was once very common; however, infection is now relatively rare. From 1991-1996, an annual average of 38 cases per year were reported. 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 less commonly associated with pork products and more often associated with eating raw or undercooked wild game meats.

How can I prevent trichinosis?

• Cook meat products until the juices run clear or to an internal temperature of 170 ^o F.

• Freeze pork less than 6 inches thick for 20 days at 5 ^o F to kill any worms.

• Cook wild game meat thoroughly. Freezing wild game meats, unlike freezing pork products, 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 with trichinosis.

• Clean meat grinders thoroughly if you prepare your own ground meats.

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

For more information:

1. Centers for Disease Control. Trichinosis Surveillance, United States, 1987-1990, MMWR 1991;40:(SS-3)35-42.

2. Moorhead A, Grunenwald PE, Dietz VJ, Schantz PM. Trichinellosis in the United States, 1991-1996: Declining but not gone. Am J Trop Med Hyg 1999; 60:66-69.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.