The reasoning: epidemiology
| Feature | Detail |
|---|---|
| Agent | Leishmania donovani (amastigotes in macrophages; promastigotes in sandfly) |
| Vector | *Phlebotomus argentipes* (female sandfly) |
| Reservoir | Humans only in the Indian subcontinent (anthroponotic); PKDL cases are important long‑term reservoirs |
| Endemic states | Bihar (most), Jharkhand, West Bengal, Uttar Pradesh |
| Risk factors | Poverty, mud houses with cracks, damp floors, cattle sheds near homes, sleeping on the floor, undernutrition, HIV co‑infection |
| Incubation | 2–6 months (10 days to years) |
| Clinical | Fever > 2 weeks, weight loss, massive splenomegaly, hepatomegaly, pancytopenia, skin darkening ("kala‑azar"), hypergammaglobulinaemia |
| PKDL | Hypopigmented macules/papules/nodules (face first) months to years after treatment; ≈ 5–15% after miltefosine/other regimens; parasites in skin → sandflies |