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 other 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 
    • 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

• Neurologic disease
  • Very uncommon
  • May manifest with myelitis, eosinophilic meningoencephalitis, seizures

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

Diagnosis

• Indications for testing - appropriate exposure and symptoms
• Clinical diagnosis may be hampered by the inability to distinguish among parasitic infections
  • Baylisascaris procyonis, Fasciola hepatica and Ascaris lumbricoides can also cause VLM
• Laboratory testing
  • IgG antibody testing indicates previous infection
  • CBC will demonstrate eosinophilia in 30% of the cases
  • Histology
    • • Tissue biopsy of involved site may demonstrate larvae which is diagnostic

Differential Diagnosis

• Pulmonary symptoms
  • Asthma
  • Other helminthic infections
  • Eosinophilic pneumonia
  • Churg-Strauss syndrome
  • Allergic bronchopulmonary aspergillosis
• Ocular
  • Granulomatous diseases such as tuberculosis, sarcoidosis
• Dermatologic symptoms
  • Dermatitis
  • Hot tub folliculitis
  • Skin infections - bacterial
  • Schistosomal dermatitis
  • Other helminthic diseases - strongyloides, loiasis