Direct and sensitive detection of Trypanosoma evansi by polymerase chain reaction

The mechanically transmitted haemoflagellate, Trypanosoma evansi causes 'su rra', a wasting disease of domestic animals and is highly endemic in distri bution in Southeast Asia. The detection of T. evansi is important for impro ving the epizootiological and animal health status of the region. The speci ficity and sensitivity of polymerase chain reaction (PCR) using oligonucleo tide primers constructed from T. evansi repetitive DNA sequences were studi ed in the present investigation. Using the assay, it was possible to amplif y template DNA of T. evansi derived from buffaloes, camels and horses to a threshold sensitivity level of 0.5 pg acid to detect DNA from as few as fiv e organisms in 10 mu l crude blood samples. Following experimental infectio n of calves with 5 x 10(5) T. evansi, positive signals could be observed as early as 12 h post-infection. DNAs from two common haemoflagellates of cat tle, Babesia bigemina and Theileria annulata were not amplified with the pr imers.