Protozoan parasites of Leishmania genus cause a severe disease, Leishmaniasis, which threatens 350 million people worldwide and some 2 million new cases occur yearly. Furthermore, mortality and morbidity from Leishmaniasis worldwide show a worrying increasing trend . Infection by the parasite Leishmania can result in a broad spectrum of pathological outcomes in the human host, ranging from simple self-healing cutaneous lesions (cutaneous Leishmaniasis, CL) to acute visceral Leishmaniasis (VL), commonly referred to as kala-azar. The different pathologies usually correlate with infection by different species . Thus, Leishmania donovani and Leishmania infantum usually cause VL, whereas the rest of Leishmania species generally cause cutaneous Leishmaniasis (CL). Nevertheless, exceptional cases have been described, such as visceral outcomes in individuals infected with L. tropica. After self-cure or successful chemotherapy, many patients remain asymptomatically infected; however, such persistence often gives rise to disease reactivation, including post-kala-azar dermal Leishmaniasis after cure of VL caused by L. donovani, diffuse cutaneous Leishmaniasis (DCL) lesions in L. mexicana-infected people, or the development of destructive mucocutaneous Leishmaniasis (espundia) months or years after healing of a localized cutaneous ulcer caused by L. braziliensis.
On the other hand, treatment outcome in patients can vary with the infecting Leishmania species because of different sensitivity of the parasite species both to the standard drugs, pentavalent antimonials and miltefosine, and those on clinical trial, paromomycin . Thus, correct diagnosis of the infecting Leishmania species is crucial for making decisions regarding prognosis and treatments, and also for epidemiological monitoring of the parasite spread .
To date, around 20 Leishmania species are known to infect humans, even though the species status is under discussion for some of them [1, 5]. In fact, a major conceptual problem in epidemiology of Leishmaniasis is the taxonomy of the etiological agent as Leishmania is a morphologically uniform genus. At present, multilocus enzyme electrophoresis (MLEE), an isoenzyme analysis that is based on 13 enzymes, is the reference method for Leishmania typing . However, MLEE has important limitations: strains with the same enzyme phenotype may have distinct amino acid sequences, the degree of relationship between different phenotypes is not known, and putative heterozygous phenotypes are difficult to interpret [6, 7]. Furthermore, this technique is time consuming, requires mass parasite culturing, and it should be done by one of the few reference centres . Therefore, its usefulness for taxonomic purposes is under dispute . In conclusion, new methods for species identification are needed to ensure proper identification and therapy.
Molecular biology techniques, such as PCR and DNA sequencing, are replacing traditional methods of taxonomy, as they tend to be more specific and easier to perform. Thus, sequencing of genes such as DNA polymerase α , RNA polymerase II , gp63 , cytochrome oxidase II [12, 13], N-acetylglucosamine-1-phosphate transferase , cystein protease b , cytochrome b [16, 17], SSU rDNA , and 7SL RNA  has been carried out for phylogenetic studies. In addition, sequencing of ribosomal DNA internal transcribed spacers [20, 21] and kinetoplast DNA minicircles  is being used for taxonomic purposes within the Leishmania genus. Remarkably, in recent studies, coding regions of genes for most metabolic enzymes used in the MLEE typing method have been determined and used for Leishmania typing [6, 23, 24]. As expected, these studies have demonstrated that DNA sequencing has greater discriminatory power than MLEE typing. Accordingly, this approach, based on sequence analysis of selected genes, has been dubbed MLST (for “multilocus sequence typing”) .
The HSP70 gene is being extensively used as a target for PCR-RFLP assays for Leishmania species discrimination [25, 26]. In fact, Montalvo and co-workers  have designed a PCR-RFLP method allowing identification of most medically relevant Old and New World Leishmania species on the basis of HSP70 PCR amplification. More recently, sequence analysis of the 1380-bp fragment of the HSP70 coding region, commonly used in the PCR-RFLP method, has been directly used for phylogenetic and taxonomic purposes [26, 28]. The phylogenetic trees obtained by da Silva et al. and Fraga et al. demonstrate that DNA sequencing of HSP70 coding regions represent a valuable technique for Leishmania species identification. As a remarkable result from these studies, Fraga and coworkers  defined eight, highly supported, monophyletic groups within the genus Leishmania: (1) L. donovani/L. infantum, (2) L. tropica/L. aethiopica, (3) L. major, (4) L. mexicana/L. amazonensis, (5) L. naiffi, (6) L. braziliensis/L. peruviana, (7) L. guyanensis/L. panamensis, and (8) L. lainsoni. Nevertheless, the HSP70 protein and the coding region of its gene are among the best conserved sequences along the evolutionary tree of life . As untranslated regions (UTR) of genes are expected to have a lower evolutionary constriction than coding regions (CDR), it is conceivable that UTR sequences may be a better target than CDR for typing of closely related organisms . In the present study, we sequenced most of the 3’-untranslated region (UTR) of Leishmania HSP70-type I (HSP70-I) gene from different species and strains with the belief that this region might be useful for species typing within the genus, having hopefully a more discriminating capacity than the HSP70 coding region.