The prevalence and diagnostic value of toxocariasis in unknown eosinophilia.

Toxocariasis is one of the causes of eosinophilia in peripheral blood and provokes eosinophilic infiltration in internal organs. Extended studies on the prevalence and clinical characteristics of toxocariasis have been rare. The aim of this study is to evaluate the prevalence of toxocariasis in unknown eosinophilia and to analyze the efficacy of toxocara enzyme-linked immunosorbent assay (ELISA). We evaluated patients presenting with peripheral blood eosinophilia (>500 cells/microl or > or =10% of white blood cell count). After checking drug histories and the presence of allergic diseases and parasitic infections, specific serum IgG antibody to Toxocara canis larval antigen was measured by ELISA. Liver and lung involvement was also evaluated. One-hundred and three patients were evaluated, and the mean age was 50.9 years old. Seventy patients (68.0%) were diagnosed as having toxocariasis. The patients who had a history of raw liver eating had a higher incidence, and the patients with liver involvement had higher serum eosinophil cationic protein values. The eosinophil count was normalized in 7 of 16 treated patients and in 25 of 54 untreated patients. The mean improvement duration was 12 months. We concluded that the prevalence of toxocariasis was high in patients with unknown eosinophilia, and the toxocara ELISA was essential for evaluation of the causes of unknown eosinophilia.