Trichinosis natural history, complications, and prognosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Danitza Lukac

Overview

If left untreated, patients with trichinosis may progress to develop periorbital edema, muscle pain, and fever. Complications of trichinosis affect the cardiovascular, neurological, ocular, respiratory and digestive systems. Most people with trichinosis have no symptoms, the infection goes away by itself. The prognosis of trichinosis is good with treatment. The most dangerous case is worms entering the central nervous system. They cannot survive there, but they may cause enough damage to produce serious neurological deficits (such as ataxia or respiratory paralysis), and even death. Infestation of the heart may also lead to death.

Natural History

• The symptoms vary depending on the phase, species of Trichinella, amount of encysted larvae ingested, age, gender, and host immunity.
• Patients infected by 10 or less larvae have either minor or no symptoms and no complications.
• Enteral/Intestinal phase:
  • From two to seven days after infection.
  • The large burden of adult worms in the intestines promote symptoms such as nausea, heartburn, dyspepsia, and diarrhea.
• Parenteral/muscle phase:
  • Seven days after infection.
  • The severity of symptoms caused by larval migration from the intestines depends on the number of larvae produced.
  • As the larvae migrate through tissue and vessels, the body's inflammatory response results in: edema, muscle pain, fever, and weakness.
  • A classic sign of trichinosis is periorbital edema, swelling around the eyes, which may be caused by vasculitis.
  • Splinter hemorrhage in the nails is also a common symptom.
  • If left untreated, the worms may cause enough damage to produce serious neurological deficits (such as ataxia or respiratory paralysis) from worms entering the central nervous system (CNS).
  • The CNS is compromised by trichinosis in 10–24% of reported cases of cerebral venous sinus thrombosis, a very rare form of stroke (3-4 cases per million annual incidence in adults).
  • Trichinosis can be fatal depending on the severity of the infection; death can occur 4–6 weeks after the infection, and is usually caused by myocarditis, encephalitis, or pneumonia.

Complications

Common complications of trichinosis include:

• Cardiovascular:
  • Heart failure
  • Heart rhythm problems (arrhythmias) from heart inflammation (myocarditis)
  • Thromboembolic disease
    • Deep thrombophlebitis
    • Intraventricular thrombi
    • Pulmonary embolism
  • Paroxysmal tachycardia
  • Pericardial effusion
• Neurological:
  • Encephalomyelitis
  • Neuromuscular disturbances:
    • Decreased muscular strength and tendon reflexes
    • Dysphagia
    • Trismus
• Ocular:
  • Edema and vascular lesions within the conjunctiva, uvea, retina, and, in some cases, the optic nerve
  • Pain when moving the eyeballs
  • Muscle paralysis
  • Diplopia
  • Disturbed accommodation
• Respiratory:
  • Dyspnea
  • Pneumonia
  • Obstructive bronchitis
  • Löffler-type infiltrates or ventilature failures
• Digestive:
  • Hypoalbuminemia
  • Acute intestinal necrosis
  • Prolonged diarrhoea

Prognosis

• Most people with trichinosis have no symptoms and the infection goes away by itself. More severe infections may be more difficult to treat, especially if the lungs, the heart, or the brain is involved.