The application of molecular biological tools to epidemiology of African trypanosomosis

Difficulties have often been encountered in the field surveys due to a lack of definitive morphological characters, particularly where mixed infections are expected. To address this problem, some molecular biological techniques such as DNA probe hybridization, restriction fragment length polymorphism (RFLP) analysis, the polymerase chain reaction (PCR), analyses of ribosomal DNA, and pulsed-field gel electrophoresis (PFGE), have been applied to the analysis of field samples collected during epidemiological surveys of African trypanosomosis. Concurrent natural infection of different individual tsetse flies and mammalian hosts with different species of the trypanosomes have been demonstrated, through the use of a combination of specific DNA probe hybridization and the PCR. Molecular karyotypes of Trypanosoma brucei species were analyzed by PFGE in 45 - 2,000 kb range. There are distinctive differences in intermediate and mini-chromosomes among the strains. We have compared the nucleotide sequences of ribosomal DNAs of the parasites by PCR techniques. From this data new phylogenetic tree can be inferred. It is apparent that these technologies can provide powerful tools for identification and diagnosis of trypanosomes in their hosts and vectors, and for their more accurate phylogenetic classification.