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| Trichinella spiralis (Owen, 1835) |
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 or rat products that are undercooked. It is also commonly associated with disease acquired from eating cougar jerky.
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Description
Trichinella species are the smallest nematode parasite of human, which has a unusual life cycle and one of the most widespread and clinically important parasites in the world. [1]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.[1]
Life cycle
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, which includes Caenorhabditis elegans, an important scientific model organism for studying genetics behind various topics such as development, neuroscience, disease, and aging.
Symptoms
The first symptoms may appear between 12 hours and two days after ingestion of infected meat. The migration of worms in the intestinal epithelium can cause traumatic damage to the host tissue and the waste products they excrete can provoke an immunological reaction.[1] The resulting inflammation can cause symptoms such as nausea, vomiting, sweating and diarrhea. Five to seven day after the appearance of symptoms facial edema and fever may occur. After 10 days intense muscular pain, difficulty breathing, weakening of pulse and blood pressure, heart damage and various nervous disorders may occur, eventually leading to death due to heart failure, respiratory complications or kidney malfunction.[1]
Diagnosis and treatment
Muscle biopsy is used for trichinosis detection. Several immunodiagnostics tests are also available. There are currently no satisfactory treatments for trichinosis, however symptoms can be relieved by use of analgesics and corticosteroids.[1]
References
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)
External links
- [1], Columbia University
- Trichina life cycle, Centers for Disease Control and Prevention
- Trichina agent, Washington University
- Fluorescence image of Trichina
Wikipedia content modification information:
- This page was last modified on 25 November 2008, at 21:17.
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