Toxocarosis is a
zoonotic disease caused by the ingestion of infective eggs of Toxocara spp. The diagnosis is based on the detection of
antibodies in serum or other
biological fluids. One of the current serological techniques for the diagnosis of
toxocariasis is ELISA using excretory - secretory
antigens of third stage larvae (ES/L3). These
antigens are
glycoproteins, which originate in the secretory organs of the parasite and are non species-specific. Sera from patients with other
helminthiases and non-
parasitic diseases were used to evaluate the specificity of ELISA using the excretory - secretory
antigen (ES/L3). The reactivity of these sera was between 11 and 70%. Western blot using patients' sera revealed that the
glycoprotein triplet having a molecular weight of 120 kDa was responsible for cross-reactivity. With these results, and for the purpose of purifying the
antigen, ion exchange chromatography was performed. When the sera from patients with various parasitic and non-
parasitic diseases were analyzed with the purified
antigen ES/ L3, they were only reactive between 10 to 20%. The sensitivity of the ELISA test determined by program Epidat 3.0 for the two
antigens was 100%, but the following differences in specificity were observed: 84% for the total
antigen ES/L3 and 99% for purified ES/L3. Using the ES/L3 purified
antigen, it can be considered that the reactive sera, with compatible symptoms correspond to patients who are or were parasitized with Toxocara canis.