Toxocara Species

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 visceral larval migrans

Laboratory Testing

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

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

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
- 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
  - Hepatosplenomegaly
  - Hypergammaglobulinemia
  - Fever
  - Pneumonitis
    - Wheezing, dyspnea
    - May manifest as transient migratory infiltrates on chest x-ray
  - Neurological disorders
    - Neurologic disease
      - Very uncommon
      - May manifest with headache, myelitis, eosinophilic meningitis/encephalitis, seizures
Ocular larval migrans
- Frequently asymptomatic
- Acute eye lesions caused by penetration of larvae into eyes
  - Vision loss in affected eye

Treatment

Treatment is required for myocardial, central nervous system and pulmonary involvement

Prevention

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

Tests generally appear in the order most useful for common clinical situations

Test name: CBC with Platelet Count & Automated Differential

ARUP #: 0040003

Methodology: Automated Cell Count with Flow Cell Differential

Use:

Assess presence of eosinophilia

Test name: Toxocara Antibody IgG by ELISA

ARUP #: 0099090

Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Diagnose and confirm T. canis infection

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

General

Hill, Harry R., MD. Group Medical Director, Laboratory of Immunology, ARUP Laboratories, and Executive Director of the ARUP Institute for Clinical and Experimental Pathology; Professor and Division Head, Pathology (Clinical), University of Utah

Comprehensive Review: October 2011
Last Update: October 2011

Central Nervous System Tumors

Churg-Strauss Syndrome