Abstract: 　Objective] To explore a simple and convenient immunoassay for early diagnosis of Toxoplasma infection.[Methods] Urine samples collected from three groups of mice infected with different doses of tachyzoites were detected for Toxoplasma circulating antigen (TCA) by dot ELISA using HRP SPA as a second antibody ( SPA ELISA).[Results] Toxoplasma circulating antigens were detected in all three groups of infected mice in contrast with the normal control group. Toxoplasma circulating antigen was detected on d 6 and d 3 after infection in mice of light and moderate infection groups, respectively.[Conclusion]SPA ELISA is a simple and convenient method for early immunodiagnosis of recent Toxoplasma infection.

Key words: Toxoplasma, circulating antigen, SPA ELISA, mouse urine.