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Table 2 Diagnostic methods for toxocariasis

From: Toxocariasis: a silent threat with a progressive public health impact

Approaches Methods Characteristics Targets Advantages Disadvantages
Direct microscopy [9, 13, 14, 133] Biopsy and visual detection of the parasite Invasive, insensitive and time-consuming Larval sections or eggs Widely available Requirement of skilled technicians
Laboratory findings [13, 134, 135] Blood biochemical analysis Should be considered in combination with clinical manifestations and further laboratory confirmation Eosinophilia (average counts of 10 000 cells/mm3, approximately 1500 cells/mm3in CT, normal range in OT or CT (< 500 cells/mm3) or eosinophil cationic protein (ECP) levels (designated as > 28 mg/L) Useful for detection of active Toxocara infections Non-specific
Antigen detection [13, 14] Sandwich ELISA Complex monoclonal antibody (MoAb) production Circulating TES Ag Useful for confirmation of active infection Low sensitivity and specificity
Antibody detection TES-Ag-ELISA A standard test for VLM and OT in reference laboratories Antibodies Good sensitivity and specificity (70–100%) [4, 13, 14, 33]. Research laboratory use only
TES-Western blot (24, 28, 30 and 35 kDa fractions of TES Ag) More specific, but less sensitivity than ELISA [33, 136]   Several commercially available kits in enzyme immunoassay, and Western-blot test formats (ELISA NOVUM, ELISA PU and Toxocara CHEK) [4]. Unavailable for discrimination of past and recent infection
Recombinant antigens Less cross-reactivity with antibodies from other helminth infections in endemic regions where poly-parasitism is common, in contrast to TES-Ag [14]. rTES-30, rTES-26 or rTES-120 [67, 136] Recommended as the best option for diagnosis of human toxocariasis [67, 137139].
Nucleic acid amplification [9] RFLP Requires a large quantity of genomic DNA, which is not readily available for parasites of small sizes, particularly larvae and eggs ITS-1 ITS-2 High sensitivity and specificity; useful for species identification and quantification of parasite burden Technically demanding, requires skilled laboratory technicians
RAPD Low reproducibility and specificity; cannot distinguish between eggs of T. canis and T. cati.
PCR The risk of carry over contamination; low throughput of samples analysis
qPCR Rapid and specific identification of T. canis and T. cati eggs in faecal and soil samples without the need for additional post-PCR manipulations
qPCR Rapid and specific identification of T. canis and T. cati eggs in fecal and soil samples without the need for additional post-PCR manipulations
LAMP A cheap, powerful and convenient approach for monitoring the contamination of soil with Toxocara eggs
  1. OT Ocular toxocariasis, CT Covert or common toxocariasis, ECP Eosinophil cationic protein, VLM Visceral larva migrans, TES-Ag Toxocara excretory secretory antigens