Sero-surveillance for surra in cattle using native surface glycoprotein antigen from Trypanosoma evansi

Surra, caused by Trypanosoma evansi affects a wide range of domestic and wild animals in the tropics, taking a huge toll on the already impoverished economy here. In bovines surra normally develops into a chronic infection that is often associated with severe production losses, yet with no distinct clinical signs making its adequate diagnosis vital. Though direct microscopic observation of T. evansi in circulation may be the diagnostic gold standard for surra, it is insensitive and impractical for population prevalence studies, making sero-diagnosis the preferred choice for the latter. In this study, we standardize an ELISA with Concanavalin-A (Con-A) affinity purified T. evansi surface glycoprotein antigen and compare its sensitivity and specificity to direct microscopy of stained thin smears and molecular (PCR) diagnostics. The ELISA was then put on field trial for sero-surveillance of cattle for surra in three geographically distinct populations in the Indian subcontinent, to yield an overall sensitivity and specificity of 100% and 89.15% compared to standard stained thin smear examinations and 95.23% and 90.84% compared to blood PCR examinations.