Trichinosis (also known as trichiniasis or trichinellosis) is an infection caused by larvae of the intestinal roundworm Trichinella spiralis. It occurs worldwide, especially in populations that eat pork or bear meat. Trichinosis may produce multiple symptoms; respiratory, central nervous system (CNS), and cardiovascular complications; and, rarely, death.
Transmission is through ingestion of uncooked or undercooked meat that contains T. spiralis cysts. Such cysts are found primarily in swine, less commonly in dogs, cats, bears, foxes, wolves, and marine animals. These cysts result from the animals' ingestion of similarly contaminated flesh. In swine, such infection results from eating table scraps or raw garbage.
After gastric juices free the worm from the cyst capsule, it reaches sexual maturity in a few days. The female roundworm burrows into the intestinal mucosa and reproduces. Larvae are then transported through the lymphatic system and the bloodstream. They become embedded as cysts in striated muscle, especially in the diaphragm, chest, arms, and legs. Human-to-human transmission doesn't take place.
Trichinosis, though common worldwide, is seldom seen in the United States because of regulations regarding animal feed and meat processing.
In the United States, trichinosis is usually mild and seldom produces symptoms. When symptoms do occur, they vary with the stage and degree of infection:
❑Stage 1 (invasion) occurs 1 week after ingestion. Release of larvae and reproduction of adult T. spiralis may cause anorexia, nausea, vomiting, diarrhea, abdominal pain, and cramps.
❑Stage 2 (dissemination) occurs 7 to 10 days after ingestion. T. spiralis penetrates the intestinal mucosa and begins to migrate to striated muscle. Signs and symptoms include edema, especially of the eyelids or face; muscle pain, particularly in extremities; and, occasionally, itching and burning skin, sweating, skin lesions, a temperature of 102° to 104° F (38.9° to 40° C), and delirium. In severe respiratory, cardiovascular, or CNS infections, palpitations and lethargy can occur.
❑Stage 3 (encystment) occurs during convalescence, generally 1 week later. T. spiralis larvae invade muscle fiber and become encysted.
A history of ingestion of raw or improperly cooked pork or pork products, with typical clinical features, suggests trichinosis, but infection may be difficult to prove. Stools may contain mature worms and larvae during the invasion stage. Skeletal muscle biopsies can show encysted larvae 10 days after ingestion; if available, analyses of contaminated meat also show larvae.
Skin testing may show a positive histamine-like reactivity 15 minutes after intradermal injection of the antigen (within 17 to 20 days after ingestion). However, such a result may remain positive for up to 5 years after exposure. Elevated acute and convalescent antibody titers (determined by flocculation tests 3 to 4 weeks after infection) confirm this diagnosis.
Other abnormal results include elevated aspartate aminotransferase, alanine aminotransferase, creatine kinase, and lactate dehydrogenase levels during the acute stages and an elevated eosinophil count (up to 15,000/µl). A normal or increased cerebrospinal fluid lymphocyte level (to 300/µl) and increased protein levels indicate CNS involvement.
Mebendazole effectively combats this parasite during the intestinal stage; severe infection (especially CNS invasion) may warrant glucocorticoids to combat possible inflammation. There's no treatment for trichinosis once it's in the muscles, but analgesics may be used for muscle pain.
❑Question the patient about recent ingestion of pork products and the methods used to store and cook them.
❑Reduce fever with alcohol rubs, tepid baths, cooling blankets, or antipyretics; relieve muscle pain with analgesics, enforced bed rest, and proper body alignment.
❑To prevent pressure ulcers, frequently reposition the patient, and gently massage bony prominences.
❑Explain the importance of bed rest. Sudden death from cardiac involvement may occur in a patient with moderate to severe infection who has resumed activity too soon. Warn the patient to continue bed rest into the convalescent stage to avoid a serious relapse and possible death.
To help prevent trichinosis:
❑Educate the public about proper cooking and storing methods not only for pork and pork products but also for meat from other carnivores. To kill trichinae, internal meat temperatures should reach 150° F (65.6° C) and meat color should change from pink to gray unless the meat has been cured or frozen for at least 10 days at low temperatures.
❑Warn travelers to foreign countries or to poor areas in the United States to avoid eating pork; swine in these areas are commonly fed raw garbage.
❑Report all cases of trichinosis to local public health authorities.
Review other book chapters online related to Trichinosis:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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