The differentiation and nomenclature of Leishmania

Abstract

1. The nomenclature and synonymy of the Leishmania of man and of the dog is reviewed.2. Many of the older names have been discarded and medical writers now recognize only two, or at the most three, species of Leishmania of man and dogs.3. These species are indistinguishable morphologically. Attempts to differentiate them by the techniques of bacteriology have given conflicting results and there is no general agreement that they can be so differentiated.4. It has been suggested that separation of species of Leishmania is not justified under the present rules of systematics and that all forms of human and canine leishmaniasis must be regarded as the result of infection by a single species of parasite.5. This suggestion is not entirely acceptable in view of contributions to the subject by medical workers who have studied the results of infection in the human subject intensively and continuously for half a century.6. Evidence is produced that the different types of human leishmaniasis recognized clinically can be correlated with biological differences in the causal parasites.7. In other organisms which have been intensively studied the existence of groups which differ from each other in biological characters only is widely recognized in modern systematics, but there is no general agreement about nomenclature for the definition of such groups.8. Reasons, not inconsistent with modern studies in systematics, are given for the recognition of at least three groups in the Leishmania of man, corresponding with the L. donovani, L. tropica and L. brasiliensis of medical text-books. Definition of the taxonomic status of such groups will depend on the further progress of systematics.