Trichinosis natural history, complications, and prognosis

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

If left untreated, infected patients develop manifestations within 1-2 days of infection. Infected patients with trichinosis may progress to develop periorbital edema, muscle pain, and fever.^[1][2] Complications of trichinosis affect the cardiovascular, neurological, ocular, respiratory, and digestive systems.^[3] Most people with trichinosis have no symptoms, the infection is usually self-limited. The prognosis of trichinosis is good with adequate treatment.^[4]

• Trichinosis is usually self-limited, and the majority of individuals with trichinosis are asymptomatic.
• 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.

• 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.

• The parental phase starts approximately 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.
• 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.^[1][2]

Common complications of trichinosis include:^[3]

• Heart failure
• Heart rhythm problems (arrhythmias) from heart inflammation (myocarditis)
• Thromboembolic disease
  • Deep thrombophlebitis
  • Intraventricular thrombi
  • Pulmonary embolism
• Paroxysmal tachycardia
• Pericardial effusion

• Encephalomyelitis
• Neuromuscular disturbances:
  • Decreased muscular strength and tendon reflexes
  • Dysphagia
  • Trismus

• 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

• Dyspnea
• Pneumonia
• Obstructive bronchitis
• Löffler-type infiltrates or ventilature failures

• Hypoalbuminemia
• Acute intestinal necrosis
• Prolonged diarrhoea

• The prognosis of trichinosis is good with adequate treatment.
• Most people with trichinosis have no symptoms, the infection is usually self-limited.^[4]
• The mortality rate of trichinosis is approximately 0.2% worldwide.^[6]
• Prompt treatment with antiparasitic drugs can help prevent the progression of trichinosis by killing the adult worms and so preventing further release of larvae.
• Once the ”Trichinella” larvae have become established in skeletal muscle cells, usually by 3 to 4 weeks post infection, treatment may not completely eliminate the infection and associated symptoms.
• If trichinosis treatment is not initiated within the first several days of infection, more prolonged or repeated courses of treatment may be necessary.^[7]