DNA-based methods in the detection of Leishmania parasites: field applications and practicalities

As conventional methods for the detection and/or diagnosis of infections with Leishmania parasites have limitations, the DNA-based alternatives have received much attention. By targeting multi-copy sequences such as kinetoplast DNA, ribosomal RNA genes, mini-exon-derived RNA genes or genomic repeats, the sensitivity of these systems can be increased. Similarly, by targeting conserved or variable regions of these targets, the specificity can be tailored to the genus, complex, species or even the individual isolate level. There are two main approaches to DNA-based detection: DNA probes involving hybridization; and amplification approaches such as PCR. DNA probes are less sensitive than amplification but are useful for large-scale screening of sandfly vectors or reservoir hosts, for example. PCR is much more sensitive and has been used for patient diagnosis with a sensitivity greater than microscopy or culture. The application of DNA probes and PCR can be simplified using chemiluminescent or colorimetric end-points, respectively, but both techniques require some specialized equipment and a certain degree of technical expertise. For this reason, their use is limited to research laboratories or central diagnostic facilities.