Leishmania species

At a time when little was understood about the leishmaniases, the complications of various indistinguishable Leishmania species and different clinical manifestations caused considerable confusion. The situation was further complicated both by the fact that most species of Leishmania infect at least one mammal other than man and by uncertainty in identifying the several species of sand flies that are Leishmania vectors. Taken together, these problems trans-... 

A simple assay for the detection of the malarial parasite Plasmodium falciparum involves saponin lysis of blood sample and membrane filtration followed by amplification of the consensus sequence of eight 21-bp repeats. This procedure has been successfully used in the field (F2). A PCR assay targeting kinetoplast DNA sequences of Leishmania species was also successfully tested in the field (F2). Molecular methods for the detection of toxoplasma gondii and several other parasites have been reviewed (F2). 

Many pathogenic protozoa. Including Trypanosoma brucei (trypanosomiasis or African sleeping sickness), Plasmodium falciparum (malaria), Leishmania species (leishmaniasis), and the intestinal parasites Giardia lamblia and Entamoeba histolytica, depend on farnesylated proteins for growth... 

Pearson RD, De Queiroz Souza A, Jeronimo SMB. Leishmania species Visceral (kala-azar), cutaneous, and mucosal leishmaniasis. In Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases, 5th ed. New York, Churchill-Livingstone, 2000 2831-2845. 

Zilberstein, D. (1991) Adaptation of Leishmania species to an acidic environment. In Biochemical Protozoology (eds Coombs, G. H. and North, M. J.), Taylor and Francis, London, pp. 349-358. 

Leishmania species possess the unique salvage etrzyme, purine nucleoside phosphotransferase. This enz5mie phosphorylates allopuritrol riboside to form the corresponding nucleotide, which interferes with puritre and nucleic acid metabolism. The answer is (B). 

There are more than 20 Leishmania species that are pathogenic to humans, and about 70 sandfly species have been implicated as vectors which transmit the parasites. There are two main epidemiological endties the zoonotic type which includes animal reservoirs, and the... 

Although any Leishmania species is capable of causing more than one form of the disease, there is a strong tendency for pardcular species to cause a pardcular disease phenotype (Table 1). 

Figure 1. Purine salvage pathways of Leishmania species. Enzymes 1) phosphoribosyltransferase 2) adenine deaminase 3) guanine deaminase 4) adenosine deaminase 5) nucleoside kinase 6, nucleotidase 7) AMP deaminase 8) adenylosuccinate synthetase 9) adenylosuccinate lyase 10) AMP kinase 11) GMP kinase 12) IMP dehydrogenase 13) GMP synthetase 14) GMP reductase.

It therefore appears that the Lxishmania parasites possess multiple routes for salvaging purines and all the purine bases are interconvertible with an apparent branch point at IMP. Hence, the Leishmania species, unlike some other protozoa, when cultured in vitro, do not require any particular purine base for growth. 

Several of the Kinetoplastida (protozoa which possess a characteristic organelle containing extra-chromosomal DNA, the kinetoplast) can be induced to differentiate in vitro. Both Trypanosoma species and Leishmania species belong to this category, and have proved to be most suitable for studies of the effects of enzyme inhibitors. 

Leishmania species exist in several morphological forms the non-motile amastigote which normally grows inside mammalian macrophages, and the promastigote which proliferates inside the insect vector and is motile... 

That the cells of both Leishmania species remain motile when grown on even the highest agar concentrations could be demonstrated by removing cells from a colony with a sterile pipet or metal loop and examining them under the light microscope. 

The protozoan parasites of family Trypanosomatidae and order Kinetoplastida are responsible for three main clinical syndromes of leishmaniasis cutaneous (caused by Leishmania tropica and L. mexicana), mucocutaneous (caused by L. braziliensis), and visceral (caused by L. donovani). The Leishmania species, L. tropica and L. donovani found in Africa, Europe, and Asia, are often termed as the Old World, while the species L. mexicana and L. braziliensis are restricted to the America and commonly referred to as the New World [3]. The visceral leishmaniasis (VL) has an estimated incidence of 500,000 new cases and 60,000 deaths each year with more than 90% of cases are centralized to India, Bangladesh, Nepal, Sudan, and Brazil [4],... 

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