Surra Sero K-SeT, a new immunochromatographic test for serodiagnosis of Trypanosoma evansi infection in domestic animals

Trypanosoma evansi, the causative agent of surra, infects different domestic and wild animals and has a wide geographical distribution. It is mechanically transmitted mainly by haematophagous flies. Parasitological techniques are commonly used for the diagnosis of surra but have limited sensitivity. Therefore, serodiagnosis based on the detection of T. evansi specific antibodies is recommended by the World Organisation for Animal Health (OIE). Recently, we developed a new antibody detection test for the serodiagnosis of T. evansi infection, the Surra Sero K-SeT. Surra Sero K-SeT is an immunochromatographic test (ICT) that makes use of recombinant variant surface glycoprotein rVSG RoTat 1.2, produced in the yeast Pichia pastoris. In this study, we compared the diagnostic accuracy of the Surra Sero K-SeT and the Card Agglutination Test for T. evansi Trypanosomososis (CATT/T. evansi) with immune trypanolysis (TL) as reference test on a total of 806 sera from camels, water buffaloes, horses, bovines, sheep, dogs and alpacas. Test agreement was highest between Surra Sero K-SeT and TL (κ=0.91, 95% CI 0.841-0.979) and somewhat lower between CATT/T. evansi and TL (κ=0.85, 95% CI 0.785-0.922) and Surra Sero K-SeT and CATT/T. evansi (κ=0.81, 95% CI 0.742-0.878). The Surra Sero K-SeT displayed a somewhat lower overall specificity than CATT/T. evansi (94.8% versus 98.3%, χ(2)=13.37, p<0.001) but a considerably higher sensitivity (98.1% versus 84.4%, χ(2)=33.39, p<0.001). We conclude that the Surra Sero K-SeT may become an alternative for the CATT/T. evansi for sensitive detection of antibodies against T. evansi in domestic animals.