The biochemical and serological taxonomy of visceralizing Leishmania

Abstract

Some intrinsic biochemical and serological characters of 84 leishmanial stocks isolated in the Old and New World from human visceral cases, dogs and wild animals thought to be reservoirs of human visceral leishmaniasis were determined, in an attempt to resolve some of the outstanding taxonomical and epidemiological problems associated with these parasites. The characters measured were nuclear and kinetoplast DNA buoyant densities, excreted factor (EF) serotypes and electrophoretic mobilities of the enzymes: malate dehydrogenase (MDH), glucose phosphate isomerase (GPI), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), in most cases, and phosphoglucomutase (PGM), alkaline phosphatase (ALP) and nonspecific esterase (NSE) in selected representatives from each major geographical region considered.

All but eight of the strains tested were biochemically and serologically similar; with some variation seen in single enzymes in a few cases and a serological difference seen in some of the Indian strains. Of the distinctly different strains, four came from Israeli visceral cases and one from an Indian visceral case and these were all biochemically and serologically identical to Iraqi, Turkestani and Indian L. tropica (=L. t. minor) strains. The ability of L. tropica-like organisms to visceralize in addition to causing simple cutaneous leishmaniasis and leishmaniasis recidivans is considered a new and important finding.

The results of this survey are discussed in relation to the classical definition of species based on clinical and epidemiological criteria and geographical origins.

The nomenclature of the causative agents of human visceral leishmaniasis is discussed.