Evaluation and improvement of parasitological tests for Trypanosoma evansi infection

Research was undertaken to critically evaluate parasitological tests for the detection of Trypanosoma evansi in blood. The relative sensitivity of mouse inoculation (MI), the haematocrit centrifugation technique (HCT) and a modified miniature anion-exchange centrifugation technique (MAECT) were compared using blood and buffy coat. The effect that storage of blood prior to inoculation into mice has on the reliability of the MI test was also evaluated. The tests may be ranked in increasing order of sensitivity: HCT, MAECT with whole blood, MI with whole blood, MAECT with buffy coat and MI with buffy coat. The latter was able to detect 1.25 T. evansi per 4ml of blood. The reliability of the MI test was not reduced with storage of blood containing at least 25 T. evansi per ml for up to 21h prior to inoculation into mice. These results demonstrate that sensitivity of the MI and MAECT are increased approximately 10-fold through the use of buffy coat in place of whole blood. Although, the MI is marginally more sensitive MAECT is better suited to field use.