A serological follow-up study was carried out on 27 children (1-12 years old) with visceral and/or ocular
toxocariasis,
after treatment with
thiabendazole. A total of 159 serum samples were collected in a period ranging from 22-116 months.
Enzyme-linked
immunosorbent assays (
IgG,
IgA, and
IgE ELISA) were standardized, using excretory-secretory
antigens obtained from the second-stage larvae of a Toxocara canis culture. The sensitivity found for the
IgG,
IgA, and
IgE ELISA, as determined in visceral
toxocariasis patients, was 100%, 47.8%, and 78.3%, respectively. Approximately 84% of the patients presented single or multiple parasitosis, as diagnosed by stool examination, yet such variables did not appear to affect the anti-Toxocara immune response. Titers of specific
IgE antibody showed a significant decrease during the first year
after treatment, followed by a decrease in the
IgA titers in the second year, and in the
IgG titers from the fourth year onwards. Sera from all patients presented high avidity
IgG antibodies, indicating that they were in the chronic phase of the disease. Moreover, 1 year
after treatment, the level of leukocytes, eosinophils, and anti-A isohemagglutinin in patients decreased significantly. The present data suggest that
IgE antibodies plus eosinophil counts are helpful parameters for patient follow-up after
chemotherapy.