Immunodiagnostic approaches for the detection of human toxocarosis.

Human toxocarosis is an important zoonosis caused by larvae of Toxocara canis/cati. The objective was to evaluate the role of IgG anti-Toxocara antibody detection and the specific IgG avidity in diagnostics of human toxocarosis. Anti-Toxocara IgG antibodies and IgG avidity were evaluated by excretory-secretory (ES)-enzyme-linked immunosorbent assay (ELISA). The IgG anti-Toxocara seroprevalence in people (n = 7678) from western Slovakia was 15.3% and found to be highest in the oldest age groups. The presence of low- IgG avidity in 179 suspected patients for toxocarosis was evaluated in relation to sex, age, IgG antibody levels, eosinophilia, increased total IgE, domicile, geophagia, dog/cat ownership, anamnesis. Low- IgG avidity index was found in 30.7% of the patients. The low- IgG avidity in eosinophilic group (42.1%) was significantly higher than in non-eosinophilic group (22.0%; P = 0.043). Substantially higher eosinophilia was detected in children (under 10 years old; 55.6%) than in adults (aged ≥ 41 years; 17.6%; P = 0.009). Significant difference between seroprevalence of total IgE in patients coming from towns (48.8%) and patients from villages (21.3%) was established (P = 0.007). Mild negative correlation (r = -0.477, P = 0.043) was observed between the amounts of eosinophils and the values of IgG avidity. The sensitivity and specificity of IgG avidity assay were 43.8% and 83.3%, respectively. Our results suggest that besides anti-Toxocara IgG, measurement of IgG avidity may be useful for the determination of acute toxocarosis. Moreover, these tests should be accompanied by other immunological markers and determinants of examined patients such as eosinophilia, increased total IgE and age.