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To differentiate between acute and past Toxocara canis infections, a modified enzyme-linked immunosorbent assay, based on the dissociation of antigen-antibody complex with 6 M urea solution was used to measure levels of avidity of specific immunoglobulin G antibody against Toxocara canis excretory-secretory antigen. IgG avidity index was determined in the sera of 212 patients, divided into two groups with various stages of Toxocara infection. Patients were classified according to time period, from the onset of clinical symptoms or first positive serology result. Low IgG avidity index was found in the sera of 6.6% of patients in the acute phase, and all samples from the chronic stage of infection were characterized by high avidity values above 0.5 (mean 0.74). It was documented, that the avidity test for specific IgG antibodies is a valuable diagnostic method that helps to distinguish the early from the later phase of Toxocara canis infection. Indications for anti-parasitic treatment according to immunological activity of Toxocara infection were discussed.

The paper is presenting the selected problems regarding clinical pathology of ophthalmic toxocariasis, as well as methods of its diagnosis, especially immunodiagnosis. The outline of contemporary treatment of this entity is also presented. The data involves the description of Toxocara's life development cycle and data regarding epidemiology of this zoonosis as well.

Mice were infected with Toxocara canis by an oral administration of embryonated eggs of the parasite, then they were killed between 1st and 8th week after infection to obtain sera and splenic lymphocytes. The lymphocytes were kept in culture medium for 3 to 6 days with either concanavalin A or excretory-secretory antigen of T. canis and assayed for proliferative responses. The obtained sera were examined for the presence of specific IgG and IgM antibodies. It was found that cell-mediated immunity was depressed for 3 weeks after infection and the first signs of the developing immunity were detected only at the 4th week of infection. Subsequently, the blastogenic responses increased reaching a level significantly higher when compared with those of the control cultures at 8th week of infection. Specific toxocaral IgG and IgM antibodies were first detected in the samples collected at the 4th week.

In order to improve the immunodiagnosis of toxocariasis, an immunoenzymatic assay (ELISA) with excretory-secretory antigens from Toxocara canis larvae was developed for the detection of specific immunoglobulin E. Titers of IgE were lower than those of IgG in the same samples, however IgE ELISA appeared to be more specific. IgE ELISA might be an interesting complementary method in the diagnosis of toxocariasis.