Trichinosis

Key Features

Essentials of Diagnosis

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

• Fever, periorbital edema, myalgia, and marked eosinophilia

General Considerations

• 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

Clinical Findings

Symptoms and Signs

• 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

Differential Diagnosis

• Gastrointestinal pathogens

• Serum sickness

• Dermatomyositis

• Typhoid fever

• Sinusitis (facial swelling is unilateral)

• Influenza with myopathy

• Toxocariasis

• Invasive schistosomiasis

Diagnosis

• 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

Treatment

• 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

Outcome

Complications

• Myocarditis

• Thromboembolic disease

• Encephalitis

Prevention

• 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.

Prognosis

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