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Identification :
Since the creation of the genus Leishmania by Ross (1903), the
number of species described has constantly increased. As the different
species are indistinguishable by their morphology, other criteria have
been used for their identification. Lumsden distinguished between extrinsic
characters (such as clinical features, geographical distribution, behaviour
in culture, laboratory animals or vectors) and intrinsic ones (such as
immunological, biochemical or molecular criteria) (1974). Among them,
isoenzyme electrophoresis remains the current gold standard technique,
while DNA-based techniques are being used increasingly.
Isoenzymatic electrophoresis :
Malate dehydrogenase electrophoretic mobility in Leishmania was
priorly studied by Gardener et al. (1974). Isoenzyme analysis was then
extented by increasing the number of enzymatic systems used. The existence
of stable and relatively specific electromorphs lead to the characterization
of the strains by their enzymatic profiles, and their grouping within
homogeneous electrophoretic taxonomic units, called zymodemes (Godfrey,
1979).
Isoenzyme electrophoresis is presently the reference technique for Leishmania
identification, at specific and infra-specific level. Moreover, the application
of numerical taxonomy techniques to electrophoresis data lead to establishment
of numerical classifications (Lanotte et al.,1981).
Molecular criteria :
Since the early technique of DNA buoyant density, molecular identification
techniques were largely diversified, but their basic principle remaining
to compare the nucleotidic sequences of the different species.
Since about 15 years, restriction fragment lenght polymorphism (RFLP),
combining several probes to different restriction enzymes made possible
the identification of different Old and New World Leishmania species.
Technical adaptations including in situ hybridization, touch-blot, dot-blot,
etc. were developed for identification of Leishmania species from
patients, infected animals and sandflies.
More recently, polymerase chain reaction (PCR) techniques, possibly associated
with DNA sequencing, are widely used for the analysis of highly unstable
genomic regions (intergenic sequences, kinetoplastic DNA, setellites DNA,
etc.) permitting the differentiation and identification of genetically
close strains.
Classification :
Various types of classification have been successively applied to
the genus Leishmania. Those proposed between 1916 and 1987 were
monothetic Linnean classifications based on few hierarchical characters.
Lainson and Shaw are the authors who worked the most on these types of
classification and who made them evolutive. Their last classification
(1987) divided the genus Leishmania into two sub-genera : Leishmania
sensu stricto, present in both Old and New World, and Viannia, restricted
to New World. Within these two sub-genera various species complexes were
individualized.
Since the 1980s, Adansonian phenetic classifications have been employed.
They are based on a number of similarly weighted characters (absence of
hierarchy) used simultaneously (polythetic classification) without a prior
hypothesis. They were at first phenetic ; subsequently, phylogenetic classification
revealed a parental relationship between the different species of Leishmania.
The phenetic, and particularly the cladistic classifications confirmed
the majority of the taxonomic groups previously established by the Linnean
classifications. The concordance between them mutually validated the extrinsic
and intrinsic identification criteria. However, cladistic analysis allowed
a more detailed study of some groups and lead to the establishment of
new complexes (L. infantum, L. turanica and L. guyanensis), and
also to the grouping in the same complex of taxa previously separated
(L. guyanensis, L. panamensis and L. shawi).
Simplified classification of the genus Leishmania, derived from
the phylogenetic analysis of Rioux et al. based on isoenzymes (1990).
I. Sub-genus Leishmania Ross, 1903
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L. donovani complex
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L. donovani (Laveran & Mesnil, 1903)
L. archibaldi Castellani & Chalmers , 1919
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L. infantum complex
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L. infantum Nicolle, 1908
(syn. L. chagasi Cunha & Chagas, 1937)
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L. tropica complex
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L. tropica (Wright, 1903)
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L. killicki complex
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L. killicki Rioux, Lanotte & Pratlong,
1986
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L. aethiopica complex
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L. aethiopica Bray, Ashford & Bray,
1973
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L. major complex
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L. major Yakimoff & Schokhor, 1914
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L. turanica complex
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L. turanica Strelkova, Peters & Evans,
1990
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L. gerbilli complex
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L. gerbilli Wang, Qu & Guan, 1964
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L. arabica complex
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L. arabica Peters, Elbihari & Evans,
1986
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L. mexicana complex
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L. mexicana Biagi, 1953
(syn. L. pifanoi Medina & Romero, 1959)
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L. amazonensis complex
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L. amazonensis Lainson & Shaw, 1972
(syn. L. garnhami Scorza et al., 1979)
L. aristidesi Lainson & Shaw, 1979
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L. enriettii complex
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L. enriettii Muniz & Medina, 1948
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L. hertigi complex
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L. hertigi Herrer, 1971
L. deanei Lainson & Shaw, 1977
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II. Sub-genus Viannia Lainson and Shaw, 1987
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L. braziliensis complex
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L. braziliensis Vianna, 1911.
L. peruviana Velez, 1913
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L. guyanensis complex
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L. guyanensis Floch, 1954
L. panamensis Lainson & Shaw, 1972
L. shawi Lainson et al., 1989
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L. naiffi complex
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L. naiffi Lainson & Shaw, 1989
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L. lainsoni complex
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L. lainsoni Silveira et al., 1987
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References :
Cupolillo E, Grimaldi G Jr, Momen H. A general classification of New
World Leishmania using numerical zymotaxonomy. Am J trop Med Hyg
1994;50:296-311.
Gardener PJ, Chance ML, Peters W. Biochemical taxonomy of Leishmania.
II. Electrophoretic variation of malate dehydrogenase. Ann trop Med Parasit
1974;68:317-325.
Godfrey DG. The zymodemes of trypanosomes. In : Problems in the identification
of parasites and their vectors. Proceedings of the Symposium of the British
Society of Parasitology 1979:17:31-53.
Lainson R, Shaw JJ. Evolution, classification and geographical distribution.
In: Peters W, Killick-Kendrick R, eds. The leishmaniases in Biology and
Medicine. London: Academic Press; 1987; 1:1-120.
Lanotte G, Rioux JA, Maazoun R, Pasteur N, Pratlong F, Lepart J. Application
de la méthode numérique à la taxonomie du genre Leishmania
Ross,1903. A propos de 146 souches originaires de l'Ancien Monde.Utilisation
des allozymes. Corollaires épidémiologiques et phylétiques.
[Application of the numerical method to taxonomy of the genus Leishmania
Ross, 1903]. Annls Parasitol hum comp 1981;56:575-592.
Le Blancq SM, Cibulkis RE, Peters W. Leishmania in the Old World.
5. Numerical analysis of isoenzyme data. Trans R Soc trop Med Hyg 1986;80:517-524.
Lumsden WHR. Biochemical taxonomy of Leishmania. Trans R Soc Trop
Med Hyg 1974; 68:74-75.
Rioux JA, Lanotte G, Serres E, Pratlong F, Bastien P, Perieres J. Taxonomy
of Leishmania. Use of isoenzymes. Suggestions for a new classification.
Annls Parasitol hum comp 1990;65:111-125.
Ross R. Note on the bodies recently described by Leishman and Donovan.
Brit Med J 1903; 2:1261-1262.
Thomaz-Soccol V. (1993). Les Leishmania du Nouveau Monde. Analyse
enzymatique. Démarche progressive phénétique-cladistique.
Relations phylogénétiques avec les Leishmania de
l'Ancien Monde. [New World Leishmania. Enzymatic analysis. Progressive
phenetic and cladistic approach. Phylogenetic relationships with Old World
Leishmania]. PHD Thesis University Montpellier I, 190 p.
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