Detection of antigens and anti-Toxocara canis antibodies in children with different asthma severities

Introduction Toxocara canis can produce or exacerbate asthma, and the detection of anti-T. canis immunoglobulin G (IgG) does not discriminate between recent infection or active larva migrans. In this study, we searched for T. canis third-stage larval antigens (L3TES) and anti-T. canis antibodies in children with different severities of asthma, controlled or uncontrolled. Methods A total of 145 patients with asthma who were previously diagnosed using the Global Initiative for Asthma guidelines were included. The asthma control was evaluated with the Asthma Control Questionnaire (ACQ). Enzyme-linked immunosorbent assay was performed for the detection of L3TES; IgG was detected using sera preadsorbed with Ascaris antigens (native kit), and a commercial kit (IgG) was used as the gold standard. Results L3TES was found in 2 patients (1.37%). One had L3TES and anti-T. canis IgG, suggesting active larva migrans. In the other patient, only L3TES was detected, likely because an infection had begun. The seroprevalence with the commercial kit and native kit was 6.2% and 17.93%, respectively. There was no significant association among asthma severity, ACQ and T. canis seroprevalence (p > .05). Conclusion It is possible to detect L3TES in patients with asthma. Two complementary techniques that can determine the infection status with T. canis and rule out cross-reactions involve the detection of L3TES and IgG using sera preadsorbed with Ascaris antigen. There was no significant association among asthma severity, ACQ and T. canis seroprevalence.