leishmaniasis

leishmaniasis
Name	Leishmaniasis
Caption	Life cycle of Leishmania parasites
Field	Infectious disease, Tropical medicine
Symptoms	Skin sores, fever, low red blood cells, enlarged spleen and liver
Complications	Disfigurement, secondary infection, bleeding
Types	Cutaneous, mucocutaneous, visceral
Causes	Leishmania parasites spread by sandfly bites
Risks	Poverty, malnutrition, deforestation, urbanization
Diagnosis	Microscopic examination, culture, serology, PCR
Differential	Leprosy, cutaneous tuberculosis, histoplasmosis, malaria
Prevention	Insecticide-treated nets, vector control, vaccines
Treatment	Antimonials, amphotericin B, miltefosine, paromomycin
Frequency	~1 million new cases/year
Deaths	20,000–30,000/year

leishmaniasis is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. The disease is transmitted through the bite of infected female sandflies and manifests in several clinical forms, primarily affecting the skin, mucous membranes, and internal organs. It is endemic in parts of the Americas, the Mediterranean Basin, East Africa, and Asia, posing a significant public health challenge in many developing countries.

Overview

The disease has been known since ancient times, with descriptions of skin lesions found in texts from the Inca Empire and the Ottoman Empire. Modern understanding began with the work of physicians like William Boog Leishman and Charles Donovan, who independently discovered the causative parasite in the early 20th century. The World Health Organization classifies it as a neglected tropical disease, with efforts coordinated by groups like the Drugs for Neglected Diseases Initiative and the International Federation of Red Cross and Red Crescent Societies.

Causes and transmission

The etiological agents are over 20 species of obligate intracellular parasites belonging to the genus Leishmania. These parasites are transmitted during the blood meal of infected female sandflies, primarily from genera such as Phlebotomus in the Old World and Lutzomyia in the New World. Transmission cycles can be zoonotic, involving animal reservoirs like rodents and canids, or anthroponotic, maintained between humans and sandflies. Other rare transmission routes include blood transfusion, congenital infection, and needlestick injury.

Clinical manifestations

The disease presents in three main forms. Cutaneous leishmaniasis, the most common, causes skin ulcers on exposed body parts, often leaving permanent scars; it is frequently caused by species like Leishmania major and Leishmania tropica. Mucocutaneous leishmaniasis, caused by species such as Leishmania braziliensis, can destroy mucous membranes of the nose, mouth, and throat years after the initial skin lesion. Visceral leishmaniasis, also known as kala-azar and caused by Leishmania donovani or Leishmania infantum, is the most severe form, characterized by irregular fever, weight loss, hepatosplenomegaly, and pancytopenia, and is fatal if untreated.

Diagnosis

Diagnosis relies on identifying the parasite or detecting an immune response. For cutaneous disease, microscopic examination of stained tissue smears or biopsy specimens is common, while culture in media like Novy-MacNeal-Nicolle medium can be used. Serological tests such as the direct agglutination test and rK39 dipstick are valuable for visceral leishmaniasis, particularly in regions like India and Sudan. Molecular techniques like PCR offer high sensitivity and are used in reference laboratories, including those affiliated with the Centers for Disease Control and Prevention.

Treatment and prevention

Treatment depends on the form, parasite species, and geographic location. Pentavalent antimonial compounds like sodium stibogluconate have been first-line drugs for decades. Alternatives include liposomal amphotericin B, the oral agent miltefosine, and paromomycin. Prevention focuses on vector control using insecticide-spraying and bed nets, and managing animal reservoirs. No licensed vaccine exists for humans, though research is ongoing at institutions like the National Institutes of Health and the Institut Pasteur.

Epidemiology

The disease is endemic in nearly 100 countries across tropical and subtropical regions. Major foci include Brazil, India, Sudan, Ethiopia, and Afghanistan. An estimated 1 million new cases occur annually, with over 1 billion people at risk. Visceral leishmaniasis is epidemic in parts of the Indian subcontinent and East Africa, while cutaneous forms are widespread in the Middle East and Central Asia. Factors like climate change, urbanization, and human migration influence its spread, with outbreaks reported in conflict zones like Syria and among refugees.

Category:Neglected tropical diseases Category:Parasitic diseases Category:Zoonoses