Alternative names: Trichiniasis or trichinellosis.
Anyone who eats undercooked meat of infected animals can develop trichinosis. Pork products are implicated more often than other meats.
Trichinae are tiny roundworms found in the muscle of infected animals, usually pigs, that cause trichinosis, a disease characterized by intestinal disorders, fever, muscular swelling, pain and insomnia.
The threadlike worms spend most of their lives curled up inside a protective capsule or cyst in muscle tissue. When the meat is eaten, the digestive juices in the stomach free these encysted worms or larvae from their capsules. They then pass into the small intestine where they develop into mature males and females in about 2 days. After mating, the females give birth to large numbers of young (called larvae), starting about the sixth day after infection. One female will give birth to between 1,000 and 1,500 larvae. These microscopic young worms penetrate the lining of the intestines, pass into the lymphatic system or the blood, and are carried to the heart. From there they are carried throughout the body by the circulating blood. They have an attraction for muscular tissue, so they invade the striated (voluntary) muscles of the body. They grow there for about 3 weeks, then coil up tightly, and in about 30 days develop a protective capsule – thus completing the cycle.
The worms can remain in this encysted form for many years – ready to infect any mammal that might eat the muscle tissue. Trichinae are about 1⁄250 of an inch long when they are born. When they reach the muscle tissue, they grow to a length of 1⁄25 inch, coiling up in a cyst about 1⁄50 inch long. When they develop into adult males and females in the intestine, they are about 1⁄8 and 1⁄6 inch long, respectively.
Animals such as pigs, dogs, cats, rats and many wild animals including fox, wolf and polar bear may harbor the parasite. When parasites are passed in the feces, they infect new animals. When humans eat infected pork that has been improperly cooked, they become infected. Improperly cooked wild animal meat may also be responsible for infecting humans. Person-to-person spread does not occur.
The symptoms usually start with fever, muscle pain/soreness (especially muscle pain when breathing, chewing, or using large muscles), pain and swelling around the eyes. Thirst, profuse sweating, chills, weakness and tiredness may develop. Chest pain may be experienced since the parasite may become imbedded in the diaphragm (the thin muscle separating the lungs from abdominal organs). Additional symptoms include abdominal discomfort, cramping and diarrhea. The incubation period varies depending upon the number of parasites in the meat and the amount eaten. It can range from five to 45 days but is usually 10 to 14 days.
There is no specific treatment for trichinosis once the larvae have invaded the muscles.
The best means of prevention is to make sure that pork (and other) products are properly cooked. If you eat pork, be careful since even a small uncooked portion can lead to infection. Always cook pork until it's well done, the desirable temperature being at least 150°F. Storing infected meat in a freezer with a temperature no higher than -13°F for 10 days will also destroy the parasite.
Most people with trichinosis have no symptoms and their infection resolves on its own. More severe infections may be more difficult to treat, especially if the lungs, the heart, and/or the brain is involved.
Trichinosis can result in death when infection is heavy – although fewer than 2% of all reported cases are fatal. Partial immunity may develop from infection, but failure to treat can be fatal.
Mebendazole is the standard treatment.
Analgesics can relieve the muscle pain.
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