Toxocara Species

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Appropriate exposure and symptoms

Laboratory Testing

  • Clinical diagnosis may be hampered by the inability to distinguish among parasitic infections
    • Baylisascaris procyonis, Fasciola hepatica, and Ascaris lumbricoides can also cause visceral larval migrans
  • Toxocariasis antibody detection (CDC)
  • Nonspecific
    • CBC will demonstrate eosinophilia in 30% of the cases
  • Serology
    • IgG antibody testing indicates previous infection
      • Single titer testing cannot distinguish between past and current infection

Histology

  • Tissue biopsy of involved site may demonstrate larvae (diagnostic)

Differential Diagnosis

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 – usually children 
  • Transmission – disease is acquired by ingestion of soil contaminated with embryonated Toxocara eggs

Organism

  • Toxocara species that infect humans are T. canis and 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
    • Cutaneous symptoms common – chronic prurigo, pruritus and/or urticaria and eczema
      • Symptoms persist a year or more
    • Severe and potentially fatal symptoms 
  • Ocular larval migrans
    • Frequently asymptomatic
    • Acute eye lesions caused by penetration of larvae into eyes
      • Vision loss in affected eye
  • Neural larval migrans
    • Fever, headache, seizures
  • Common larval migrans
    • Similar to VLM but less severe

Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Toxocara Antibody IgG by ELISA 0099090
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Limitations

Toxocara antibody titers in populations without clinical symptoms of visceral larval migrans vary dramatically; elevated titers alone cannot definitively establish diagnosis

Because antibody response varies depending on worm burden and location, a negative result does not necessarily rule out toxocariasis infection

Follow Up

If results equivocal, repeat testing in 10-14 days

Related Tests

General References

Akao N, Ohta N. Toxocariasis in Japan. Parasitol Int. 2007; 56(2): 87-93. PubMed

Gavignet B, Piarroux R, Aubin F, Millon L, Humbert P. Cutaneous manifestations of human toxocariasis. J Am Acad Dermatol. 2008; 59(6): 1031-42. PubMed

Gottstein B, Piarroux R. Current trends in tissue-affecting helminths. Parasite. 2008; 15(3): 291-8. PubMed

Moreira GMarçal Sc, Telmo Pde Lima, Mendonça M, Moreira ANunes, McBride AJohn Alexa, Scaini CJames, Conceição FRochedo. Human toxocariasis: current advances in diagnostics, treatment, and interventions. Trends Parasitol. 2014; 30(9): 456-64. PubMed

Rubinsky-Elefant G, Hirata CE, Yamamoto JH, Ferreira MU. Human toxocariasis: diagnosis, worldwide seroprevalences and clinical expression of the systemic and ocular forms. Ann Trop Med Parasitol. 2010; 104(1): 3-23. PubMed

Medical Reviewers

Last Update: December 2015