## Epidemiology of Kala-azar in India **Key Point:** Leishmania donovani is the exclusive causative agent of visceral leishmaniasis (kala-azar) in the Indian subcontinent, with endemic foci in Bihar, Jharkhand, and parts of Uttar Pradesh. ### Geographic Distribution | Leishmania Species | Geographic Region | Disease Type | Prevalence in India | | --- | --- | --- | --- | | L. donovani | Indian subcontinent, East Africa, Mediterranean | Visceral (kala-azar) | Endemic, especially Bihar | | L. infantum | Mediterranean, Middle East, Central Asia | Visceral (infantile) | Not endemic in India | | L. tropica | Middle East, North Africa, Central Asia | Cutaneous (urban) | Not associated with kala-azar | | L. major | Middle East, North Africa, Central Asia | Cutaneous (zoonotic) | Not associated with kala-azar | **High-Yield:** The term "kala-azar" (black fever) is pathognomonic for L. donovani visceral infection in India. The disease presents with the classic tetrad: fever, hepatosplenomegaly, pancytopenia, and hypergammaglobulinemia. ### Clinical Features in Indian Kala-azar 1. **Incubation period:** 2–8 months (range up to 10 years) 2. **Fever pattern:** Irregular, often double-spiking 3. **Organomegaly:** Hepatomegaly (95%), splenomegaly (80%) 4. **Hematologic findings:** Anemia, leukopenia, thrombocytopenia 5. **Diagnostic confirmation:** Bone marrow aspiration, splenic aspiration (highly sensitive) **Clinical Pearl:** In endemic areas of India, any child presenting with prolonged fever + hepatosplenomegaly + pancytopenia should be presumed to have kala-azar until proven otherwise. **Mnemonic:** KALA-AZAR = **K**ala (black) **A**nastigotes **L**eishmania **A**ffects **A**bdominal organs **Z**oonotic (anthroponotic in India) **A**cute **R**eticuloendothelial involvement. [cite:Park 26e Ch 7]
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