A comparative evaluation of parasitological tests and a PCR for Trypanosoma evansi diagnosis in experimentally infected water buffaloes

In this study five parasitological methods and a polymerase chain reaction (PCR) were compared for the diagnostic sensitivity for Trypanosoma evansi i n experimentally infected water buffaloes over a period of 15 weeks. The co mbined estimates of sensitivity (CEse) of the PCR proved to be highest at 7 8.2%, closely followed by the mouse inoculation (MT), the micro-haematocrit e centrifugation technique (MHCT) and the mini-anion-exchange centrifugatio n technique (MAECT) with CEse of, respectively, 74.0, 69.6 and 62.4%. The C Ese of the buffy-coat technique (BCT) at 38.6% and the sodium dodecyl sulfa te (SDS) clarification technique at 25.1% were considerably lower. PCR dete cted consistently all buffaloes infected from week 3 post-infection (PI) on wards. For MI this occurred after 5 weeks PI while for MHCT and MAECT these sustainable high levels were reached in the 7th week PI. BCT and SDS never detected all buffaloes infected. The influence of time and temperature on the viability of T. evansi in heparinized blood from water buffalo was also studied. In general we observed that the survival time tends to be longer when blood is kept at 4 degreesC, In samples kept in direct sunlight parasi tes became undetectable with the MHCT after 30 min. After treatment of the water buffaloes with diminazene aceturate, the PCR signal disappeared withi n 24 h. (C) 2001 Elsevier Science B.V. All rights reserved.