Toxocara canis infection of children: Epidemiologic and neuropsychologic findings

Sera from 4,652 children whose blood was submitted to the New York City Department of Health for lead analysis were tested for antibodies to Toxocara canis using an enzyme-linked immunosorbent assay (ELISA). Standardized to the age distribution of the study population, T. canis seropositivity (inverse titers ≥ 16) was 5.7 per cent in males and 5.1 per cent in females. T. canis antibody titers and lead exposures as measured by Centers for Disease Control lead classes were positively correlated. Children who were seropositive to T. canis (cases) were compared to seronegatives (controls) matched on age (± 6 months), sex, time-of-screening (± 3 months) and CDC lead class. Logistic regression analysis of 155 case-control pairs demonstrated elevated relative risks (RRs) for geophagia (RR = 3.14; 95% CI = 1.75, 5.64) and having had a litter of puppies in the home (RR = 5.22; 95% CI = 1.63, 16.71). Compared to controls, cases had increased eosinophil counts, serum immunoglobulin E concentrations, and anti-hemagglutinin-A titers. Small deficits in cases compared to controls were found in performance on several neuropsychological tests after adjustment for potential confounders including case-control differences in race, socioeconomic status, and current blood lead concentrations. The study thus confirmed that T. canis infection is common in urban children and suggested that infection may be associated with adverse neuropsychological effects.