Detection of circulating antigens and antibodies in Toxocara canis infection among children in Chengdu, China

In order to determine the seroprevalence of Toxocara spp. infection in chil dren from Chengdu, we performed an enzyme-linked immunosorbent assay (ELISA ) and sandwich ELISA (S-ELISA) with excretory-secretory antigens isolated f rom second-stage larvae of Toxocara canis (TES-Ag ELISA). The seroprevalenc es of T. canis antibodies in the children from rural areas, urban districts , and urban districts with recent Ascaris lumbricoides infection were 17.7% (59/333), 2.1% (4/186), and 2.6% (1/38), respectively. Among 63 suspected patients with symptoms of T. ca,lis infection, 31 had positive antibodies. The inhibition assay showed an apparent inhibiting capacity of TES-Ag for t he antibody against T. canis larvae. The result of S-ELISA demonstrated tha t circulating antigens of T: canis larvae could be detected in part of the serum with positive antibodies and that the detection rate for circulating antigens in the sera could be improved by polyethylene glycol-acid treatmen t. This is the first epidemiological study to confirm the existence of T. c anis infection and Toxocara-larvae migrans in Chengdu by the combination of TES-Ag ELISA and S-ELISA.