Development of an indirect ELISA test using a purified tachyzoite surface antigen SAG1 for sero-diagnosis of canine Toxoplasma gondii infection

The aim of this study was to use affinity purified 30 kDa Toxoplasma gondii surface antigen (SAG1) in an indirect ELISA and to compare it with an existing indirect fluorescent antibody test (IFAT). 245 serum samples were collected from dogs from three adjacent Iranian provinces. IFAT examination revealed positive results in 73 dogs, with titers ranging from 1:16 to 1:1024. A suitable ELISA cut-off was determined by ROC analysis in comparison with IFAT. Results showed a relative sensitivity and specificity of 94.52% and 93.60%, respectively, for a cut-off value of 0.790 in the ELISA. No cross-reactivity was detected between antibodies against T. gondii and a closely related protozoan parasite, Neospora caninum, using this newly developed ELISA test.