Leishmania

From Academic Kids

Leishmania
Scientific classification
Kingdom:Protista
Phylum:Euglenozoa
Order:Kinetoplastea
Family:Trypanosomatida
Genus:Leishmania
Species

see text

Leishmania is a genus of parasitic flagellate, belonging to the trypanosomes and responsible for diseases such as leishmaniasis. Leishmania is spread through sand flies, with two different vectors: Phlebotomus in the Old World, and Lutzomyia in the New World. The parasite have two morphological states: promastigote (leptimonad), which lives in the digestive tract of the fly, and amastigote, which is found in the lysosomes in the macrophages of vertebrates. Common vertebrates that are infected include hyraxes, canids, rodents, and humans. Infections are represented as cutaneous (localized and diffuse), mucocutaneous and visceral.

Cutaneous infections shown with obvious skin reactions. Most common is the Oriental Sore (L. major, L. tropica and L. aethiopica all are Old World). The common New World cutaneous culprits are L. mexicana and L. viannia braziliensis.

Mucocutaneous (espundia) infections will start off as a reaction at the bite, and can go metastasis in to the mucus membranes and be fatal.

Visceral infections (a L. donovani exclusive) are often recognized with fever, weight loss, swelling of the liver and spleen and anaemia. An important aspect to the life of the Leishmania protozoan is its glyconjugate layer of lipophosphoglycan (LPG). Held together with a phopshoinosite membrane anchor; tripartite structure, it consists of a lipid domain, a neutral hexasaccharide core and a phosphorylated galactose-mannose, with a termination in a neutral cap. Not only do the little unfriendlies not develop post-phlebotmus digestion but, it is thought to be essential to oxidative bursts, thus allowing passage for infection. Along with oxidative bursts, the parasites destroy macrophages through acidification and digestion. Chararacteristics of digestion include an endosome fusing with a lysosome, releasing acid hydrolases which degrade DNA, RNA, proteins and carbohydrates.

Visceral leishmaniasis is known by many local names, of which the most common is probably Kala azar [1] (http://homepages.uel.ac.uk/D.P.Humber/akhter/dis.htm) [2] (http://www.bartleby.com/61/51/K0005100.html)


The origins of leishmania is a well thought out subject. One scientist suggested a palaearctic migration of Leishmania into the New World. This is much like the palaearctic migration of human across the Bering Strait land bridge. Most of both theories concur. In the theory, the reservoirs are humans and rats. The humans migrate in North America and South America and leishmania picks 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 of Tennessee.

Leishmania currently affects 12 million people in 88 countries. Visceral infections are most common in Bangladesh, Brazil, India, Nepal and Sudan. Mucocutaneous infections are most common in Bolivia, Brazil and Peru. Cutaneous infections are most common in Afghanistan, Brazil, Iran, Peru, Saudi Arabia and Syria. Treatments of the disease generally involve a solution containing antimony. 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 intravenous, with the aid of sand flies and needle-sharing drugs users. Most at risk are humans infected with HIV, canines and rodents.

Species

There are many different species, including:

External links

There is a site The International Leishmania Network (ILN) (http://www.bdt.org.br/leishnet/) that has basic information on the disease and links to many aspects of the disease and its vector.

There is also a discussion list (Leish-L) (http://www.bdt.fat.org.br/listas/leish-l/) which can be subscribed to. There are 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.fr:Leishmaniose

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