The species Trichinella spiralis
is an important parasite
, occurring in rats, pigs, and humans, and is responsible for the disease trichinosis
. It is sometimes referred to as the "pork worm" due to it being found commonly in pork products that are undercooked. It is also commonly associated with disease acquired from eating cougar jerky.
Trichinella species are the smallest nematode parasite of human, which has a unusual life cycle and one of the most widespread and clinically important parasite in the world. 
The small adult worms mature in the intestine
of an intermediate host such as a pig. Each adult female produces batches of live larvae
, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system
, and are carried to striated
muscle tissue. Once in the muscle, they encyst
, or become enclosed in a capsule.
Humans can be infected by eating infected pork or wild carnivores
such as fox, cat or bear.
Larvae encysted in the muscles remain viable for some time. When the muscle tissue is eaten by a human, the cysts are digested in the stomach; the released larvae migrate to the intestine to begin a new life cycle. Female trichina worms live about six weeks and in that time may release larvae. The migration and encystment of larvae can cause fever, pain, and even death because of their potential to eat living tissue. One of the classic signs of Trichinella spiralis
infection is a combination of splinter hemorrhages
(not to be confused with those of bacterial endocarditis
) and periorbital edema (eye swelling). Trichina are classified in the phylum Nematoda
First symptoms may appear between 12 hours and two days after ingestion of infected meat. Worm migration in intestinal epithelium
cause traumatic damage to the host tissue and the host begins to react to their waste products.
Inflammation causes symptoms such as nausea, vomiting, sweating and diarrhea. Five to seven day after first symptoms facial edema
and fever may occur. By the 10th day of first symptoms intense muscular pain, difficulty breathing, weakening of pulse and blood pressure, heart damage and various nervous disorders may occur, causing death due to the heart failure, respiratory complication or kidney malfunction.
Diagnosis and treatment
Muscle biopsy is used for trichinosis detection. Several immunodiagnostics tests are also available. As of treatment, there are no satisfactory treatment for trichinosis, but only relieving the symptoms by use of analgesics and corticosteroids.
1. Roberts, Larry S., John Janovay. Foundations of Parasitology. New York: McGraw-Hill, (2005), 405-407.
2. Despommier, D.D., Gwadz, R.G, Hotez, P., Knirsch, C. Parasitic Diseases 5th ed. New York: Apple Trees Pub. (2002)