Toxocara

Toxocara

 

Toxocariasis is caused by migration of the larvae from the roundworm Toxocara to organs and tissues.  Toxocara larva migrans is the second most common helminthic infection in developed countries.

Epidemiology

  • Incidence – one of the most common parasitic infections worldwide
  • Age – affects mostly children 
  • Transmission – disease is acquired by ingestion of soil contaminated with embryonated Toxocara eggs

Organism

  • Toxocara species that infect humans are Toxocara canis (T. canis) and Toxocara cati (T. cati)
  • Ingested eggs hatch into larvae, travel across gut wall and migrate to liver or lungs through lymphatic and circulatory systems
  • Larvae then spread from lungs to organs, causing damage by their migration and induction of granulomatous lesions

Clinical Presentation

  • Visceral larval migrans (VLM)
    • Asymptomatic, with mild eosinophilia
    • Severe and potentially fatal symptoms, including
      • Hepatosplenomegaly
      • Hypergammaglobulinemia
      • Fever
      • Pneumonitis
        • Wheezing, dyspnea
        • May manifest as transient migratory infiltrates on chest X-ray
      • Neurological disorders
    • Symptoms persist a year or more
  • Ocular larval migrans (OLM)
    • Asymptomatic
    • Acute eye lesions caused by penetration of larvae into eyes
      • Vision loss in affected eye

Diagnosis

  • Clinical diagnosis may be hampered by the inability to distinguish between Toxocara and other parasitic infections
    • Baylisascaris procyonis, Fasciola hepatica and Ascaris lumbricoides can also cause VLM
  • Laboratory testing
    • IgG antibody testing indicates previous infection

Treatment

  • Treatment is required for myocardial, CNS and pulmonary involvement

Prevention includes:

  • Deworming dogs
  • Prohibiting dog excreta in parks and playground
  • Preventing pica in children