Trichinosis, also known as trichinellosis, is a parasitic disease caused by roundworms of the Trichinella type. During the initial infection, invasion of the intestines can result in diarrhea, abdominal pain, and vomiting. Migration of larvae to muscle, which occurs about a week after being infected, can cause swelling of the face, inflammation of the whites of the eyes, fever, muscle pains, and a rash. Minor infection may be without symptoms. Complications may include inflammation of heart muscle, central nervous system involvement, and inflammation of the lungs.

Trichinosis is mainly spread when undercooked meat containing Trichinella cysts is eaten. In North America this is most often bear, but infection can also occur from pork, boar, and dog meat. Several species of Trichinella can cause disease, with T. spiralis being the most common. After the infected meat has been eaten, the larvae are released from their cysts in the stomach. They then invade the wall of the small intestine, where they develop into adult worms. After one week, the females release new larvae that migrate to voluntarily controlled muscles, where they form cysts. The diagnosis is usually based on symptoms and confirmed by finding specific antibodies in the blood, or larvae on tissue biopsy.

The best way to prevent trichinosis is to fully cook meat. A food thermometer can verify that the temperature inside the meat is high enough. Infection is typically treated with antiparasitic medication such as albendazole or mebendazole. Rapid treatment may kill adult worms and thereby stop further worsening of symptoms. Both medications are considered safe, but have been associated with side effects such as bone marrow suppression. Their use during pregnancy or in children under the age of 2 years is poorly studied, but appears to be safe. Treatment with steroids is sometimes also required in severe cases. Without treatment, symptoms typically resolve within three months.

Worldwide, about 10,000 infections occur a year. At least 55 countries including the United States, China, Argentina, and Russia have had recently documented cases. While the disease occurs in the tropics, it is less common there. Rates of trichinosis in the United States have decreased from about 400 cases per year in the 1940s to 20 or fewer per year in the 2000s. The risk of death from infection is low.