LEISHMANIASIS ICD-10: B55
Etiology. Many species of obligate intracellular protozoa Leishmania; predominant species are:
New World: Leishmania mexicana complex, Viannia subgenus.
Old World: L. tropica, L. major, and 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 resulting from a particular parasite, vector, and host species.
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.
Diffuse (anergic) cutaneous leishmaniasis (DCL).
Mucosal leishmaniasis (ML).
Visceral leishmaniasis (VL); kala-azar; post–kala-azar dermal leishmaniasis (PKDL).
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).
EPIDEMIOLOGY AND ETIOLOGY
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 to 4 µm in diameter); replicates in macrophage phagosomes in mammalian hosts.
TRANSMISSION Vector-borne by bite of infected female phlebotomine sandflies, which become infected by taking blood meal from infected mammalian host. About 30 species of sandflies have been identified as vectors. They rest in dark, moist places, and are typically most active in evening and nighttime hours. Other modes: Congenital and parenteral (i.e., by blood transfusion, needle sharing, or laboratory accident).
RESERVOIRS Varies with geography and leishmanial species. Zoonosis involves rodents/canines.
VECTORS Transmitted by 30 species of female sandflies of genera Lutzomyia (New World) and Phlebotomus (Old World).
PREVALENCE An estimated 12 million people infected worldwide. According to the World Health Organization, there are 700,000–1 million new cases each year. It is thought that children are more susceptible.
GEOGRAPHY All inhabited continents except Australia; endemic in focal areas of 90 countries. Tropics, subtropics, and 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, and from rural to urban.
HOST DEFENSE DEFECTS Leishmania-specific anergy: Patients develop DCL. Poor immune response or immunosuppression (HIV disease): VL. Hyperergic variant: Leishmaniasis recidivans caused by L. tropica.
The clinical and immunologic spectrum of leishmaniasis parallels that of leprosy. CL occurs in a host with good protective immunity. MCL occurs in those with an intense inflammatory reaction. DCL occurs with extensive and widespread proliferation of the organism in the skin ...