PCR-based diagnosis of Surra using a newly identified conserved region of the variant surface glycoprotein (VSG) gene

Trypanosoma evansi, the causative agent of Surra, is the most widespread pathogenic trypanosome that parasitizes the widest variety of mammals worldwide; however, rapid and easily accessible diagnostics still need to be improved. Proteomic research identified the VSG (Variant Surface Glycoprotein) TevSTIB805.3.100 gene as a potential biomarker for T. evansi diagnosis. The aim of this study was to design primers (called Tev3.100) for the gene encoding this VSG, testing the specificity and sensitivity of these primers on genomic DNA (gDNA) from different species and on biological samples. The specificity of primers was tested against gDNA from T. evansi, T. brucei, T. equiperdum, T. rangeli, T. cruzi, T. vivax, Babesia bovis, B. bigemina, and Anaplasma sp. Seventy-one biological samples from Lageana Creole cattle DNA were used, testing the sensitivity, specificity and concordance ​​in relation to RoTat 1.2 primers. The Tev3.100 primers were able to produce amplicons with a single band of approximately 1800 bp for gDNA from T. evansi, but showed cross-reactions with T. brucei, and T. equiperdum, diverging from the in silico predictions. These primers indicated high sensitivity (98.28 %) and specificity (84.62 %) in the detection of biological samples from Lageano Creole cattle, in addition to high concordance values (κ: 0.854; SE: 0.082; 95 % CI: 0.695–1.000) in relation to RoTat primers results. The Tev3.100 primers are a new molecular tool with good sensitivity and specificity for Surra infections, but the cross-reactions with T. equiperdum, diverging from the databases, indicate that new genomic studies should be carried out for these species in Latin America.