Pediatric Toxocariasis Workup

Updated: Mar 10, 2015
  • Author: Germaine L Defendi, MD, MS, FAAP; Chief Editor: Russell W Steele, MD  more...
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Laboratory Studies

Visceral larva migrans (VLM):

Visceral larva migrans (VLM) is usually suspected in a young child who presents with fever, wheezing, and hepatomegaly. A complete blood count (CBC) with differential reveals leukocytosis and marked eosinophilia (≤80%). Other nonspecific laboratory findings are hypergammaglobulinemia (particularly IgM) and elevated isohemagglutinin titers for antigens in blood groups A and B.

Titers for Toxocara are assessed using a specific enzyme-linked immunosorbent assay (ELISA). The Toxocara Excretory-Secretory (termed TES) ELISA uses an excretory or secretory antigen from the supernatants of in vitroT. canis larvae. With a cutoff dilution of 1:32, the sensitivity of TES ELISA is approximately 75%, and its specificity is close to 92%. Specificity may be lower in tropical populations because of cross-reactivity with other helminthic diseases. Western blotting appears to be more specific but is more labor-intensive. The major pitfall of serologic tests is that they cannot be used to distinguish between current and past infections.

Antigen-capture assays with monoclonal antibodies may be helpful in diagnosing current infection but their sensitivity and specificity are not ideal.

Presently, polymerase chain reaction (PCR) has been used to detect infection, but is limited to identify Toxocara species in the tissues of animal models.

The diagnosis of VLM can be definitively confirmed by finding larvae in the affected tissue via histologic examination or by assessing the digestion of tissue. Biopsy is rarely performed, and the larvae are not always found.

Ocular larva migrans (OLM):

The diagnosis of OLM usually relies on clinical findings as the serologic diagnosis tends to be problematic. Patients with OLM have TES ELISA titers that can be negative or lower than those values seen in patients with VLM. Considering a titer greater than 1:8 as indicative for infection, the TES ELISA is 90% sensitive and 91% specific for this clinical form of toxocariasis. Clinical correlation is warranted.

Titers of ocular vitreous and aqueous humor are elevated when compared to serum levels. [18]


A definitive test for covert toxocariasis does not exist. Positive anti-Toxocara titers in the presence of malaise, chronic weakness, pulmonary symptoms, abdominal pain, or allergic signs accompanied by eosinophilia and absence of response to allergens, support this diagnosis.

Since the intestinal form of toxocariasis does not occur in humans, stool studies for ova and parasites are not helpful in the diagnosis of toxocariasis. Presence of other parasites in the stool indicates environmental and behavior risk factors for other parasitic disease.


Imaging Studies

Imaging studies in toxocariasis (VLM and OLM) depend on the body location of the disease.

  • Chest radiography is indicated in patients with wheezing and eosinophilia in whom eosinophilic pneumonia is suspected. It can also identify pleural effusions and cardiac shadow enlargement.
  • Echocardiography is used to evaluate myocardial function, which is depressed in myocarditis, and to identify the presence of pericardial fluid and intracardiac pseudotumors.
  • Abdominal ultrasonography is a good screening test to identify hepatic granulomas.
  • Ocular ultrasonography can be used to characterize T. canis ocular lesions.
  • CT scans and MRI are also used to evaluate presence of ocular and/or CNS disease.


Biopsy of the involved tissue may be helpful.


Histologic Findings

When performed, biopsy of the affected tissues reveals granulomatous lesions containing large numbers of eosinophils and neutrophils and, rarely, the remnants of dead larvae.