Microbiology

An Overview of the Nematode Parasite Trichinella Spiralis



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Parasites are organisms which benefit at the expense of other living beings (hosts).  Trichinella spiralis is a nematode (round worm) parasite.  Also called as pork worm, this parasite is found in human beings, bears, pigs and rats.  It is very common in raw or undercooked pork.  Draft of genome of Trichinells spiralis became available in the early part of 2011.  These parasites are considered clinically important.

Trichinella spiralis belongs to the genus Trichinella.  It is a relatively small nematode.  The male Trichinella spiralis measures around 1.6 mm.  Females can grow up to 4 mm.  The larva is approximately 1 mm.  Their vulva is located near the esophagus.  Female Trichinella spiralis has one uterus.  Developing eggs are found in the posterior portion of the uterus and the fully developed juveniles are found in the anterior portion.  

The small adult worms mature in the intestines of their host.  There the female Trichinella spiralis produces larvae.  These larvae enter the blood and lymphatic system and are carried to striated muscles. They feed on blood.  Once inside the muscle they enclose themselves in a capsule like cyst.  Trichinella spiralis has a direct life cycle (it completes all stages of development in one host).  Female Trichinella spiralis lives up to six weeks.  During its lifetime it produces around 1500 larvae.  

Human beings can get infected by consuming infected pork.  The larvae are released from the capsule like cyst once inside the human stomach.  This is due to the digestive juices in the stomach.  From there they migrate to the intestine, where they mature and reproduce.  Trichinella spiralis causes the disease trichinosis.  Cramps, diarrhea, nausea, vomiting, sweating, breathing difficulties, weakening of pulse, nervous disorders, fever, muscle pain and abdominal discomfort are some symptoms of this disease.  These symptoms appear at various stages.  Migration and encystment of larvae causes fever and pain in the infected person.  If the larvae migrate to certain organ tissues, the person may suffer from myocarditis (inflammation of the heart muscles) or encephalitis (acute inflammation of the brain).  The person may die.  Trichinosis is diagnosed by muscle biopsy.  Doctors use analgesics to relieve the symptoms.  They also use mebendazole or ablendazole.  There has been a steady decline in the reported incidence of trichinosis in the United States of America, thanks to various measures taken by the government.  

Reference:

www.wormbook.org

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