Detection of Trypanosoma brucei gambiense in sleeping sickness suspects byPCR amplification of expression-site-associated genes 6 and 7

We have developed a sensitive and specific method to identify Trypanosoma b rucei ssp. using PCR to amplify conserved expression-site-associated gene 6 and 7 DNA target sequences. Amplification of 10% of the DNA in a single tr ypanosome produced sufficient PCR product to be visible as a band in an aga rose gel stained with ethidium bromide. We analysed 59 blood samples of ser ologically positive cases of sleeping sickness by PCR, and directed parasit ological examination of tissue fluids. The PCR test detected 87% of the par asitologically positive cases, with a specificity of 97%. In 5 cases, the p arasite was demonstrated by the PCR rest 4-6 months prior to parasitologica l detection. This result shows the potential of the assay in early diagnosi s of actual T. b. gambiense infections in apparently aparasitaemic sleeping sickness patients.