Validation of the indirect TaSP enzyme-linked immunosorbent assay for diagnosis of Theileria annulata infection in cattle.

An ELISA based on a recombinant Theileria annulata surface protein (TaSP) was evaluated for detection of antibodies in sera from cattle exposed to tropical theileriosis in Sudan. The reference positive samples, used in this study, were from Theileria-infected populations and consisted of 80 cattle from an endemic area in Khartoum State, with high antibody titers in the indirect fluorescent antibody test (IFAT). The reference negative samples were taken from non-exposed populations and consisted of 120 cattle maintained under strict tick control at a commercial farm in Sudan. The cut-off value determined by Two-Graph Receiver-Operating Characteristic (TG-ROC) curves was set at 31.6%, based on the positive reference samples. Further diagnostic validation was performed, which consisted of the measurement of the area under the ROC (AUC) and by valid range proportion (VRP), which was 0.97 and 0.98 for the cut-off, respectively. There were no cross-reactions with antibodies raised against Babesia spp. It is concluded that the TaSP ELISA is a useful test for the diagnosis of T. annulata infection in cattle under field conditions.