Colloidal Dye Immunobinding Assay for Detection of Trypanosoma evansi Antibodies in Animals

Abstract

Colloidal dye immunobinding assay (CDIA) was developed for detection of circulatory antibodies of Trypanosoma evansi in the sera of domestic animals. Specific antibodies in the serum were captured by T. evansi antigen spotted on to nitro cellulose membrane mounted on a flow through device. The bound antibodies were visualised by the addition of protein A colloidal gold conjugate which imparts pink colour to the membrane. The optimum concentrations of antigen, test serum and colloidal dye protein A conjugate in the assay were standardized. The efficacy of CDIA was determined by comparing with the results of indirect ELISA. CDIA could detect T. evansi antibodies in 261 ﴾cattle (n=92), buffaloes (n=132) and sheep (n=37) ﴿ serum samples out of 290 ﴾cattle (n=100), buffaloes (n=140) and sheep (n=50) ﴿ indirect ELISA positive samples. All the 22 samples found positive for T. evansi infection by Wet blood film (WBF) examination were also found to be positive by CDIA. The diagnostic sensitivity and diagnostic specificity of CDIA were recorded as 90.00 and 100 per cent, respectively. The CDIA developed in the present study for detection of T. evansi infection in domestic animals is simple to perform, rapid, could potentially applied in all host species, economical and suitable for a wide variety of field applications without any sophisticated instrumentation.