Prueba de avidez de los anticuerpos IgG en la infección por Toxocara canis

in order to evaluate the usefulness of the igg avidity test to recognize the phase of t. canis human infection in individuals highly exposed to the parasite, 142 asymptomatic children of both sexes, 1-6 years old, living in resistencia (northeastern argentina), with eosinophilia > 10% and without helminthic intestinal infestation were studied. elisa-igg test was performed in all cases, and in those with serological titers > 1/80 igg avidity was also measured. out of 142 children studied, 82 (57.7%) were positive to elisa test, but only 6 (7.3%) had an igg avidity index < 50%. five of them were aged between 1 to 2 years and the other was 5 years old (median 1.5 years). four had moderate serological titers (between 1/80 and 1/640) and two had high titers (between 1/1280 and 1/10240). the other 76 children with igg avidity indexes > 50% were between 18 months and 5.5 years old (median 4 years), 44 had moderate serological titers and 32 had high titers. the results found in this study reaffirm that the population in resistencia city is highly exposed to t. canis infection and that the igg avidity test may be helpful in differential diagnosis of recent and past toxocariosis, though it would be more effective to rule out a recently acquired infection than to confirm it.