Human toxocariasis in a rural community.

A questionnaire and serologic survey of a Pennsylvania community revealed that 23 (54%) of 43 study participants had antibody titers to Toxocara canis (enzyme-linked immunosorbent assay test [ELISA]) in the range defined as positive (greater than or equal to 1:32). Age-specific seropositivity rates were highest among adults (greater than or equal to 18 years). Positive titers ranged from 1:32 to 1:512. Seropositivity did not cluster by family, and seropositivity rates were significantly higher than those of a control group. Physical examination and laboratory tests designed to detect clinical signs of toxocariasis were performed on individuals with positive ELISA titers. Nine of 23 had a history of pica, seizures, or chronic pulmonary symptoms; however, physical examination revealed no abnormalities. Although medical examination and laboratory tests revealed a few abnormalities, neither the visceral larva migrans syndrome nor the ocular lesions characteristic of those produced by Toxocara sp were observed in any individual. We conclude that although certain populations may have high seropositivity rates to Toxocara antigens, indicating previous infection, clinical diseases may be uncommon.