Characterization of Leishmania (Leishmania) waltoni n.sp. (Kinetoplastida: Trypanosomatidae), the Parasite Responsible for Diffuse Cutaneous Leishmaniasis in the Dominican Republic

Abstract

Leishmania parasites isolated, between 1979 and 1988 by the late Bryce Walton, from Dominican Republic (DR) patients with diffuse cutaneous leishmaniasis, were characterized using a panel of 12 isoenzymes, 23 monoclonal antibodies, small subunit ribosomal DNA (SSu rDNA), and multilocus sequence analysis (MLSA). The isoenzyme and monoclonal antibody profiles and the MLSA results showed that the Dominican Republic parasites were distinct from other described Leishmania species. This new species belongs to the mexicana complex, which is distributed in central and parts of northern South America. It is suggested that the parasites uniqueness from other members of the mexicana complex is related to it being isolated on an island for millions of years. If Leishmania (Leishmania) waltoni fails to adapt to some imported mammal, such as the house rat, it will be the only Leishmania to be classified as an endangered species. The excessive destruction of habitats on Hispaniola threatens the survival of its vectors and presumed natural reservoirs, such as the rodent hutias and the small insectivorous mammal solenodon. The concept of Leishmania species is discussed in the light of recent evaluations on criteria for defining bacterial species.

Figure 1.

Phylogenetic tree of the New World Leishmania sub-genus, with mention of the evolutive steps. (1: L. (L.) aristidesi, 2: L. (L.) waltoni).

Figure 2.

Maximum likelihood tree of the concatenated nucleotide sequences of 16 Leishmania strains. Significant bootstrap values are shown in percentage on each node. The species/taxonomic names, the geographical origins and the zymodemes are shown for each strain. The five L. (L.) waltoni strains fall into a highly supported cluster (BP 99%). The L numbers correspond to the National Reference Code Leishmania (NRCL) codes: for correspondence to the World Health Organization (WHO) codes, see Table 1. ND = not determined.