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Leishmaniasis

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ICD-9: 085.9 ○ ICD-10: B55 Image not available.

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  • Etiology. Many species of obligate intracellular protozoa Leishmania; predominant species are:

    • New World: Leishmania mexicana complex, Viannia subgenus

    • Old World: L. tropica, L. major, L. aethiopica

  • Vector. Sandflies. Old World: Phlebotomus. New World: Lutzomyia

  • Pathogenesis. Infection of macrophages in skin, naso-oropharyngeal mucosa, and the reticuloendothelial system (viscera). Diversity of clinical syndromes due to particular parasite, vector, and host species.

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Clinical Syndromes

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Cutaneous leishmaniasis (CL) characterized by development of single or multiple cutaneous papules at the site of a sandfly bite, often evolving into nodules and ulcers, which heal spontaneously with a depressed scar.

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  • New World cutaneous leishmaniasis (NWCL)

  • Old World cutaneous leishmaniasis (OWCL)

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Diffuse (anergic) cutaneous leishmaniasis (DCL)

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Mucosal leishmaniasis (ML)

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Visceral leishmaniasis (VL); kala-azar; post–kala-azar dermal leishmaniasis (PKDL)

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Synonyms: NWCL: chiclero ulcer, pian bois (bush yaws), uta. OWCL: Baghdad/Delhi boil or button, oriental/Aleppo sore/evil, bouton d’Orient. ML: Espundia. VL: Kala-azar (Hindu for black fever)

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Epidemiology and Etiology

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Infection in humans is caused by 20 Leishmania species (Leishmania and Viannia subgenera). Stages of parasite: Promastigote: flagellated form found in sandflies and culture; amastigote: nonflagellated tissue form (2–4 μm in diameter); replicates in macrophage phagosomes in mammalian hosts.

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Transmission
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Vector-borne by bite of infected female phlebotomine sandflies (2–3 mm long), which become infected by taking blood meal from infected mammalian host. About 30 species of sandflies have been identified as vectors. Sandflies are weak noiseless fliers; they rest in dark, moist places, typically most active in evening and nighttime hours. Other modes: congenital and parenteral (i.e., by blood transfusion, needle sharing, laboratory accident).

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Reservoirs
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Varies with geography and leishmanial species. Zoonosis involves rodents/canines.

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Vectors
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Transmitted by 30 species of female sandflies of genus genera Lutzomyia (New World) and Phlebotomus (Old World).

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Prevalence
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Estimated 12 million people infected worldwide. 1.5–2 million new cases annually; 350 million individuals are at risk of infection. 50% of new cases are in children. 75,000 individuals die annually of ML.

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Geography
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All inhabited continents except Australia; endemic in focal areas of 90 countries. Tropics, subtropics, southern Europe. More than 90% of cases of CL occur in Afghanistan, Algeria, Iran, Iraq, Saudi Arabia, Syria, Brazil, and Peru. Climates: Range from deserts to rain forests, rural to urban.

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Host Defense Defects
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Leishmania-specific anergy: patients develop DCL. Poor immune response or immunosuppression (HIV disease): VL. Hyperergic variant: Leishmaniasis recidivans caused by L. tropica.

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Pathogenesis
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The clinical and immunologic spectrum of leishmaniasis parallels that of leprosy. CL occurs in a ...

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