Toxocariasis in an institution for the mentally retarded

A seroepidemiologic investigation was conducted in order to determine the cause of an apparent increase in rates of eosinophilia among 1400 institutionalized children during 1976-1977. The annual serologic survey during this period revealed 283 (20%) individuals with eosinophilia that exceeded 600 cells/cu mm of blood. During a five-month period in 1977, five patients who were hospitalized in adjacent wards developed acute pneumonia with eosinophilia. Because laboratory tests of sputum, bone marrow, and stool failed to identify the etiologic agent, it was thought that these pneumonia cases might be related to the increased rates of eosinophilia. Analyses of random samples of sera from patients with eosinophilia revealed seroprevalence rates of 12% for Ascaris, 20% for Toxocara canis, 24% for Strongyloides stercoralis, and 32% with increased antibody to Entamoeba histolytica. Further investigation showed a statistically significant positive association between occurrence of eosinophilia and pica behavior, and eosinophilia and contact with dogs. Although the serologic survey showed patients to have had previous exposure to a variety of parasites, we hypothesize that a principal cause of eosinophilia among institutionalized children may be Toxocara infestation, due to their frequent pica behavior and, in this case, contact with resident animals. We recommend that children in similar facilities have limited contact with pet dogs, and only after frequent and vigorous examination of the animals for infectious parasites.