Leishmania
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 Leishmania donovani in bone marrow cell.
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Leishmania is a genus of trypanosome protozoa, and is the parasite responsible for the disease leishmaniasis. It is spread through sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. Their primary hosts are vertebrates; 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, Brazil, Iran, Peru, 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 [1] [2], 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 glycoconjugate layer of liphosphoglycan (LPG). This is held together with a phosphoinositide 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 these parasites develop post-phlebotomus digestion but, it is thought to be essential to oxidative bursts, thus allowing passage for infection. Chararacteristics of intracellular 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 antimony, 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 much discussed subject and theories vary. One proposes an African origin, with migration to the Americas. Another migration from the Americas to the Old World about 15My ago, across 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.
[edit] Species
There are many different species, including:
- Leishmania aethiopica
- Leishmania amazonensis
- Leishmania arabica
- Leishmania archibaldi (disputed species)
- Leishmania aristedesi
- Leishmania (Viannia) braziliensis
- Leishmania chagasi (syn. Leishmania infantum)
- 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
- Leishmania (Viannia) lainsoni
- Leishmania major
- Leishmania mexicana
- Leishmania (Viannia) naiffi
- Leishmania (Viannia) panamensis
- Leishmania (Viannia) peruviana
- Leishmania (Viannia) pifanoi
- Leishmania (Viannia) shawi
- Leishmania tarentolae
- Leishmania tropica
- Leishmania turanica
- Leishmania venezuelensis
[edit] Leishmania as component of CVBD
CVBD stands for Canine Vector-borne Diseases. This covers diseases caused by pathogens transmitted by ectoparasites as ticks, fleas, sand flies or mosquitoes.
Other diseases caused by ectoparasites:
- Bartonella
- Borrelia
- Babesia
- Dirofilaria
- Ehrlichia
- Anaplasma
[edit] External links
- The International Leishmania Network (ILN) has basic information on the disease and links to many aspects of the disease and its vector.
- A discussion list (Leish-L) is also available with over 600 subscribers to the list, ranging from molecular biologists to public health workers, from many countries both inside and outside endemic regions. Comments and questions are welcomed.
- KBD: Kinetoplastid Biology and Disease, is a website devoted to leishmaniasis, sleeping sickness and Chagas (American leishmaniasis). It contains free access to full length peer review articles on these subjects. The site contains many articles relating to the unique kinetoplastid organelle and genetic material therein.[[ja:リーシュマニ��原虫]]
