Leishmania
Leishmania est un genre proche des trypanosomes. C'est un parasite des mammifères transmis par la piqure de phlébotomes et responsable d'une maladie, la leishmaniose.
Histoire
Le parasite a été nommé en 1903 d'après le nom du biologiste écossais William Boog Leishman[réf. souhaitée].
Épidémiologie
Leishmania touche actuellement 12 millions de personnes dans 98 pays. L'incidence est d’approximativement 2 millions de cas par an. Il y a 21 espèces responsables des infections chez l'humain.
Certaines leishmanioses touchent d'autres mammifères que l'homme, et en particulier les canidés, par exemple la leishmaniose canine (en) chez le chien, notamment en Europe autour de la Méditerranée[réf. souhaitée].
Évolution
Les détails de l'évolution du genre Leishmania ne sont pas très clairs, mais il est supposé qu'il ait une origine commune ancestrale avec le genre Trypanosoma. Le plus ancien taxon est celui de la famille des Bodonidae suivi par Trypanosoma brucei : ces espèces récentes sont limitées au continent africain. Le groupe de Trypanosoma cruzi avec les trypanosomes présents chez des chauves-souris, des mammifères de l'Amérique du Sud et chez des kangourous suggèrent une origine dans l'hémisphère sud.
Les sous-groupes restants sont Blastocrithidia, Herpetomonas et Phytomonas. Les quatre genres Leptomonas, Crithidia, Leishmania et Endotrypanum semblent avoir une origine commune[1].
Les origines du genre Leishmania ne sont pas suffisamment définies[2],[3]. Une hypothèse propose une origine africaine, avec une migration vers les Amériques. Une autre hypothèse propose la migration des Amériques, il y a 15 millions d'années, traversant le détroit de Béring. Une autre théorie propose une origine paléarctique[4],[5]. C'est bien la cause des épidémies actuellement beaucoup plus évidentes[6],[7].
Un autre sous-groupe proche de Leishmania est Paraleishmania[8].
Texte anglais à traduire :
It is spread through sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. They primary hosts is a vertebrate; Leishmania commonly infects hyraxes, canids, rodents, and humans. Leishmania currently affects 12 million people in 88 countries.
Leishmania cells have two morphological forms: promastigote (with an anterior flagellum) in the insect host, and amastigote (without flagella) in the vertebrate host. Infections are regarded as cutaneous, mucocutaneous, or visceral:
- Cutaneous (localized and diffuse) infections appear as obvious skin reactions. The most common is the Oriental Sore (caused by Old World species L. major, L. tropica, and L. aethiopica). In the New World, the most common culprits are L. mexicana and L. (Viannia) braziliensis. Cutaneous infections are most common in Afghanistan, Brésil, Iran, Pérou, Saudi Arabia and Syria.
- Mucocutaneous (espundia) infections will start off as a reaction at the bite, and can go metastasis into the mucous membrane and become fatal. Mucocutaneous infections are most common in Bolivia, Brazil and Peru.
- Visceral infections are often recognized by fever, weight loss, swelling of the liver and spleen, and anemia. They are known by many local names, of which the most common is probably Kala azar , and are caused exclusively by species of the L. donovani complex (L. donovani, L. infantum syn. L. chagasi). Visceral infections are most common in Bangladesh, Brazil, India, Nepal and Sudan.
An important aspect of the Leishmania protozoan is its glyconjugate layer of liphosphoglycan (LPG). This is held together with a phosphoinosite membrane anchor, and has a tripartite structure consisting of a lipid domain, a neutral hexasaccharide, and a phosphrorylated galactose-mannose, with a termination in a neutral cap. Not only do the little unfriendlies not develop post-phlebotomus digestion but, it is thought to be essential to oxidative bursts, thus allowing passage for infection. Chararacteristics of digestion include an endosome fusing with a lysosome, releasing acid hydrolases which degrade DNA, RNA, proteins and carbohydrates.
Treatments of the disease generally involve a solution containing antimoine, which is toxic. A solution which breaks down the LPG is also a form of treatment being looked at. Those who feel they are infected should seek immediate attention. Transmission is mainly through the bite of sand flies but also through needle-sharing by drugs users. Most at risk are humans infected with HIV, canines and rodents.
The origins of Leishmania are a well thought out subject. Theories vary. One proposes an African orgin, with migration to the Americas. Another migration from the Americas to the Old World about 15My ago, accross the Bering Strait land bridge. Another proposes a palaearctic origin. Such migrations would entail migration of vector and reservoir or successive adaptations along the way. A more recent migration is that of L. infantum from Mediterranean countries to Latin America (there named L. chagasi), since European colonization of the New World, where the parasites picked up its current New World vectors in their respective ecologies. This is the cause of the epidemics now evident. One recent New World epidemic concerns foxhounds in the USA.
Espèces
Il y a de nombreuses espèces différentes. De plus, il peut exister des hybrides entre espèces ; un hybride possible a été signalé au Brésil entre Leishmania (V.) guyanensis et Leishmania (V.) shawi shawi[9].
Liste partielle des espèces :
- Leishmania aethiopica
- Leishmania amazonensis
- Leishmania arabica
- Leishmania archibaldi (discutable)[10]
- Leishmania aristedes
- Leishmania (Viannia) braziliensis
- Leishmania chagasi (= Leishmania infantum)[11]
- Leishmania (Viannia) colombiensis
- Leishmania deanei
- Leishmania donovani
- Leishmania enriettii
- Leishmania equatorensis
- Leishmania forattinii
- Leishmania garnhami
- Leishmania gerbili
- Leishmania (Viannia) guyanensis
- Leishmania herreri
- Leishmania hertigi
- Leishmania infantum
- Leishmania killicki (discutable)[12]
- Leishmania (Viannia) lainsoni
- Leishmania major
- Leishmania martiniquensis[13]
- Leishmania mexicana
- Leishmania (Viannia) naiffi
- Leishmania (Viannia) panamensis
- Leishmania (Viannia) peruviana
- Leishmania (Viannia) pifanoi
- Leishmania (Viannia) shawi
- Leishmania turanica
- Leishmania tropica
- Leishmania venezuelensis
Notes et références
- (en) Hughes AL, Piontkivska H., « Phylogeny of Trypanosomatidae and Bodonidae (Kinetoplastida) based on 18S rRNA: evidence for paraphyly of Trypanosoma and six other genera », Mol Biol Evol., vol. 20, no 4, , p. 644-652
- (en) Momen H, Cupolillo E, « Speculations on the origin and evolution of the genus Leishmania », Mem Inst Oswaldo Cruz., vol. 95, no 4, , p. 583–8. (PMID 10904419, DOI 10.1590/S0074-02762000000400023)
- Noyes HA, Morrison DA, Chance ML, Ellis JT, « Evidence for a neotropical origin of Leishmania », Mem Inst Oswaldo Cruz., vol. 95, no 4, , p. 575–8. (PMID 10904417, DOI 10.1590/S0074-02762000000400021)
- (en) Kerr SF, « Palaearctic origin of Leishmania », Mem. Inst. Oswaldo Cruz, vol. 95, no 1, , p. 75–80 (PMID 10656708, DOI 10.1590/S0074-02762000000100011)
- Katrin Kuhls, Alam, Mohammad Zahangir; Cupolillo, Elisa; Ferreira, Gabriel Eduardo M.; Mauricio, Isabel L.; Oddone, Rolando; Feliciangeli, M. Dora; Wirth, Thierry; Miles, Michael A.; Schönian, Gabriele; Kamhawi, Shaden, « Comparative Microsatellite Typing of New World Leishmania infantum Reveals Low Heterogeneity among Populations and Its Recent Old World Origin », PLoS Neglected Tropical Diseases, vol. 5, no 6, , e1155 (DOI 10.1371/journal.pntd.0001155)
- DOI:10.3201/eid1203.050811
- (en) Noyes HA, Arana BA, Chance ML, Maingon R (1997) « The Leishmania hertigi (Kinetoplastida; Trypanosomatidae) complex and the lizard Leishmania: their classification and evidence for a neotropical origin of the Leishmania-Endotrypanum clade » J Eukaryot Microbiol. 44(5):511-557
- (en) Momen H, Cupolillo E (2000) « Speculations on the origin and evolution of the genus Leishmania » Mem Inst Oswaldo Cruz 95(4):583-588
- Jennings, Y. L., de Souza, A. A. A., Ishikawa, E. A., Shaw, J., Lainson, R. & Silveira, F. 2014: Phenotypic characterization of Leishmania spp. causing cutaneous leishmaniasis in the lower Amazon region, western Pará state, Brazil, reveals a putative hybrid parasite, Leishmania (Viannia) guyanensis × Leishmania (Viannia) shawi shawi. Parasite, 21, 39. DOI:10.1051/parasite/2014039
- (en) Kuhls K. et al., « Analysis of ribosomal DNA internal transcribed spacer sequences of the Leishmania donovani complex », Microbes and Infection, vol. 7, nos 11-12, , p. 1224-34.
- (en) Lukeš J. et al., « Evolutionary and geographical history of the Leishmania donovani complex with a revision of current taxonomy », Proceedings of the National Academy of Sciences, vol. 104, no 22, , p. 9375-80. (DOI 10.1073/pnas.0703678104)
- (en) Schönian G. et al., « Leishmaniases in the Mediterranean in the era of molecular epidemiology », Trends in Parasitology, vol. 24, no 3, , p. 135-42. (DOI 10.1016/j.pt.2007.12.006)
- N. Desbois, F. Pratlong, D. Quist et JP. Dedet, « Leishmania (Leishmania) martiniquensis n. sp. (Kinetoplastida: Trypanosomatidae), description of the parasite responsible for cutaneous leishmaniasis in Martinique Island (French West Indies). », Parasite, vol. 21, , p. 12 (PMID 24626346, PMCID 3952653, DOI 10.1051/parasite/2014011)
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