Life Cycle

< Infection occurs by ingesting encysted larvae in undercooked meat.

< The larvae excyst and develop to adults in the small intestine.
< Adults attach to the intestinal mucosa and being to release larvae in one week.  The adults live for about 4 weeks and may release more than 1000 larvae.
Microscopy of Trichinella spiralis
< Larvae penetrate the intestinal wall and move to muscle tissue where they encyst in individual cells (nurse cells).  Active muscles, such as the diaphragm and tongue, often have the greatest numbers of larvae.


Infection with Trichinella spiralis may be asymptomatic, especially in light infections.  Adults in the intestine may cause diarrhea, abdominal pain, and vomiting.  Larvae moving into the tissues may cause facial swelling, fever, muscle pain, splinter hemorrages (under fingernails) or rashes.

Heavy infections may lead to heart problems or central nervous system involvement.  Large numbers of larvae in other muscles may lead to soreness and weakness which often lessens over time.

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