Trichinosis

Also called trichiniasis and trichinelliasis, trichinosis is a chronic infection that occurs worldwide. It's especially common in populations that eat pork or bear meat. It is caused by eating raw or undercooked pork and wild game products which are infected with the larvae of a species of worm called Trichinella spiralis. Infection occurs worldwide, but is most common in areas where raw or undercooked pork, such as ham or sausage, is eaten.

Causes

Trichinosis is caused by larvae of the intestinal roundworm Trichinella spiralis. Transmission occurs through ingestion of uncooked or undercooked meat that contains T.spiralis cysts. Such cysts are found primarily in swine and less often in dogs, cats, bears, horses, ,wild boars, foxes, wolves, and marine animals. These cysts result from the animals' ingestion of similarly contaminated flesh. In swine, eating table scraps or raw garbage causes such infection. Human-to-human transmission doesn't occur.

After the T.spiralis cyst enters the body, gastric juices free the worm from the cyst capsule. It reaches sexual maturity in a few days. Then the female roundworm burrows into the intestinal mucosa and reproduces. The larvae are transported through the lymphatic system and the bloodstream. They become embedded as cysts in striated muscle, especially in the diaphragm, chest, arms, and legs.

Signs and Symptoms

• Abdominal discomfort
• Cramping
• Diarrhea
• Fever
• History of having eaten rare or uncooked pork (bear and other wild carnivores or omnivores)
• Muscle pain (especially muscle pain with breathing, chewing, or using large muscles)

Diagnostic tests 

To confirm the diagnosis, your doctor may use these tests:

• Blood tests. Your doctor may take a blood sample and test it for signs of trichinosis.
• Muscle biopsy. While the blood test typically is enough to establish a diagnosis, your doctor may also need to do a muscle biopsy. A very small piece of muscle, weighing about 1 gram, is removed and examined under a microscope to look for trichinella larvae.

Treatment

Current anthelmintic drugs are ineffective against trichinella larvae in muscle. Mebendazole is active against the enteric stages of the parasite. Glucocorticoids are beneficial in severe myosites and myocarditis. This disease usually is self-limiting, and complete recovery occurs within a few months.                                

Supportive therapy, such as bed rest, administration of salicylates, and physical therapy to maintain and enhance muscle function, usually proves effective.

If symptoms persist for several years, the patient may need mebendazole therapy. He'll need corticosteroids only if he has a fever, allergic symptoms, leukocytosis, and eosinophilia.

Prevention

Pork and meat from wild animals should be cooked until well done. Freezing at subzero temperatures (Fahrenheit) for 3 to 4 weeks will kill the organism. Smoking, salting, or drying meat are not reliable methods of preventing this infections.

Cook all meat fed to pigs or other wild animals and do not allow hogs to eat uncooked carcasses of other animals, including rats (which may be infected with trichinosis).