Kala-azar

Kala-azar, medically termed visceral leishmaniasis (VL), constitutes the most severe clinical form of leishmaniasis infection. The disease is caused by obligate intracellular protozoan parasites of the genus Leishmania, specifically L. donovani in East Africa and the Indian subcontinent, and L. infantum (also designated L. chagasi) in Europe, North Africa, and Latin America. The parasite's visceral tropism distinguishes this form from cutaneous and mucocutaneous leishmaniasis, as the organism preferentially migrates to and multiplies within the reticuloendothelial system of internal organs.

The clinical syndrome of visceral leishmaniasis is characterized by systemic parasitism of the liver, spleen, and bone marrow, producing a constellation of constitutional and organ-specific manifestations. Prominent symptoms include persistent fever, progressive weight loss, fatigue, and anemia, accompanied by substantial hepatosplenomegaly—particularly enlargement of the spleen, which represents the most typical presenting finding. The hyperpigmentation that inspired the Hindi-derived name 'kala-azar' (black sickness) is notably absent in most geographic strains of the parasite. Without treatment, the disease follows a uniformly fatal course, though direct parasite effects are rarely the proximate cause of death; rather, mortality typically results from secondary infections including pneumonia, tuberculosis, and dysentery in immunocompromised hosts. The emergence of HIV/VL co-infection has been identified by WHO as a particularly concerning development in the epidemiological landscape.

Visceral leishmaniasis ranks as the second-largest parasitic killer worldwide, trailing only malaria in attributable mortality with an estimated 20,000 to 30,000 deaths occurring annually. The disease exhibits a broad geographic distribution corresponding to the habitat range of competent sandfly vectors, spanning tropical and temperate regions across multiple continents. Endemic foci are concentrated in resource-limited settings where healthcare infrastructure constrains access to definitive diagnosis and treatment. The disease burden is compounded by diagnostic challenges and the immunosuppressive conditions prevalent in endemic regions, which facilitate both primary infection and the particularly dangerous intersection of leishmaniasis with HIV co-infection.

The transmission cycle of visceral leishmaniasis involves two obligatory hosts: humans (or alternative mammalian reservoirs) and phlebotomine sandflies of the genus Phlebotomus in the Old World and Lutzomyia in the New World. Adult female sandflies, measuring 3–6 mm in length, serve as biological vectors by acquiring amastigote forms during blood meals on infected hosts. Within the sandfly midgut, the parasite transforms into motile promastigote forms that migrate to the proboscis, enabling transmission to subsequent hosts during subsequent blood-feeding episodes. Lutzomyia longipalpis has been identified as the primary vector in New World transmission settings.

Populations residing in sandfly-endemic regions face elevated exposure risk, particularly in tropical and temperate areas where vector density coincides with human habitation. Immunocompromised individuals, including those with HIV infection, represent a particularly vulnerable subgroup with increased susceptibility to severe disease and poorer treatment outcomes. The convergence of HIV/VL co-infection has been identified by WHO as an emerging threat that complicates both clinical management and epidemiological surveillance.

Source-backed detail regarding specific prevention measures is not yet available in the provided source material. General vector avoidance strategies appropriate for sandfly-endemic areas would include personal protective measures during peak biting periods (typically nocturnal hours), environmental management to reduce breeding sites, and community-level vector control initiatives. Historical therapeutic advances include the synthesis of urea stibamine by Upendranath Brahmachari in 1922, which provided an effective antimony-based treatment alternative for L. donovani infection.

Surveillance for visceral leishmaniasis requires consideration of both diagnostic limitations and epidemiological context. The gold standard for parasitological confirmation remains microscopic visualization of amastigotes in splenic or bone marrow aspirates, though this approach carries significant procedural risks, discomfort, and resource requirements that limit its applicability in field settings. Serological rapid diagnostic tests, particularly the rK39 immunochromatographic assay, have demonstrated 92% sensitivity in confirming active infection and are more commonly employed in endemic areas. However, serological testing presents challenges in distinguishing active infection from past exposure, and false-negative results remain a concern. The disease's clinical presentation frequently mimics malaria, creating diagnostic confusion that may delay appropriate treatment and contribute to underascertainment in surveillance systems.

1. 1 Wikidata. visceral leishmaniasis.
2. 2 Wikipedia. Visceral leishmaniasis - Wikipedia.

ICD-10

B55

ICD-11

1F51

Total cases

5K

Total deaths

12

Peak month

2015-11

Coverage

1 reporting countries · 2010-01-01 → 2026-04-01