Development of a recombinant TaSP-based Dot-ELISA for detection of Theileria annulata infection in cattle.

The study was conducted to develop and validate Dot-ELISA for the diagnosis of Theileria annulata infection in cattle using recombinant Theileria annulata surface protein (r-TaSP). The r-TaSP based indirect plate-ELISA was used as a reference test to compare the efficacy of the Dot-ELISA. The Dot-ELISA was optimized with 500 ng of antigen per dot, 1:150 dilution of serum and 1:1000 dilution of secondary antibody for positive and negative reaction. A total of 17 confirmed positive, 25 negative and 129 field sera samples were used to calculate the diagnostic accuracy of Dot-ELISA in comparison with indirect plate-ELISA. The diagnostic sensitivity and specificity of the Dot-ELISA was 95.8 per cent (95% CI, 93.1-97.2) and 80 per cent (95% CI, 48.1-96.2), respectively. The positive predictive value (PPV) of Dot-ELISA was 98.2 percent (95% CI, 95.5-99.7) and negative predictive value (NPV) was 61.6 percent (95% CI, 37-74). The positive and negative likelihood ratios were 4.79 (95% CI, 1.8-25.69) and 0.053 (95% CI 0.03-1.4), respectively. The Dot-ELISA showed moderate agreement (k value, 0.67, 95% CI, 0.36- 0.82) with indirect plate-ELISA. The developed Dot-ELISA is less expensive and convenient for the diagnosis of T. annulata infection in cattle under field conditions.