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Key Features

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Essentials of Diagnosis
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  • Vomiting, diarrhea, and abdominal pain within 1 week of eating infected meat

  • Fever, periorbital edema, myalgia, and marked eosinophilia

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General Considerations
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  • Trichinella are small roundworms that infest hogs and several other meat-eating animals

  • Most important source of human infection worldwide is the domestic pig, but in Europe meat from wild boars and horses caused several prominent outbreaks

  • Human cycle begins with ingestion of viable larvae in undercooked meat

    • In the intestine, the larvae develop into adult worms that mate and produce hundreds of larvae

    • The larvae enter the bloodstream and migrate to the striated muscle where they continue to grow and eventually encyst

  • Symptoms are caused by the inflammatory response in the intestines or muscle

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Clinical Findings

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Symptoms and Signs
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  • Most infections are asymptomatic

  • Severity of clinical disease is strongly correlated with the number of ingested larvae.

  • Infection can be divided into two phases: intestinal and muscular (or systemic)

  • Initial bowel penetration, occurring within 1 week after ingestion of contaminated meat, may cause

    • Fever

    • Headache

    • Chills

    • Gastrointestinal complaints

  • May progress to the classic myopathic form, which consists of fever, eyelid or facial edema, myalgia, and weakness

  • Vasculitis is leading pathologic process, which can manifest as

    • A maculopapular exanthem

    • Subungual bleeding

    • Conjunctivitis and subconjunctival hemorrhages

    • Headaches

    • Dry cough

    • Painful movement of the eye muscles

  • Symptoms usually peak after 2–3 weeks but may last for months

  • Children typically have milder clinical and laboratory findings than adults

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Differential Diagnosis
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  • Gastrointestinal pathogens

  • Serum sickness

  • Dermatomyositis

  • Typhoid fever

  • Sinusitis (facial swelling is unilateral)

  • Influenza with myopathy

  • Toxocariasis

  • Invasive schistosomiasis

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Diagnosis

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  • Based on three main criteria

    • Clinical findings (fever; myalgias; eyelid and/or facial edema; gastrointestinal symptoms; and subconjunctival, subungual, and retinal hemorrhages)

    • Laboratory findings (nonspecific eosinophilia and increased levels of muscle enzymes, antibody detection, and/or detection of larvae in a muscle biopsy)

    • Epidemiologic investigation

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Treatment

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  • Albendazole (400 mg twice daily for 8–14 days) is drug of choice

  • Mebendazole

    • An acceptable alternative

    • Dosage: 200–400 mg three times a day for 3 days followed by 400–500 mg three times a day for 10 days

  • Concurrent corticosteroids (eg, prednisone 30–60 mg/d for 10–15 days) are used for treatment of severe symptoms

  • Administration of analgesics is sometimes required

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Outcome

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Complications
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  • Myocarditis

  • Thromboembolic disease

  • Encephalitis

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Prevention
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  • All pork and sylvatic meat (eg, bear or walrus) should be cooked at least > 160°F

  • Freezing meat to at least 5°F for 3 weeks may also prevent transmission

  • Animals used for food should not be fed or allowed access to raw meat.

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Prognosis
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  • In severe cases with cardiac and cerebral complications, prognosis is poor (mortality ...

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