Describe the visceral Leishmaniasis of Kala-azar.

Definition

• Kala-azar (visceral leishmaniasis) is a chronic protozoal infection caused by Leishmania donovani, transmitted by the bite of the female sandfly (Phlebotomus).
• It is endemic in parts of eastern India (Bihar).

Clinical Features

• Prolonged (> 2 weeks) fever, often with a double rise, and progressive weakness.
• Massive splenomegaly and hepatomegaly; pancytopenia (anaemia, leucopenia, thrombocytopenia).
• Weight loss and darkening of the skin ('kala-azar' = black fever).

Investigations

• Splenic or bone-marrow aspirate — demonstrates LD bodies (amastigotes) (most specific).
• RK39 rapid antibody test (widely used); aldehyde (formol-gel) test.
• Pancytopenia and hypergammaglobulinaemia on supportive tests.

Management & Prevention

• Liposomal amphotericin B — the drug of choice.
• Miltefosine (oral) and paromomycin are alternatives.
• Post-kala-azar dermal leishmaniasis (PKDL) may follow treatment and acts as a reservoir.
• Prevention — vector (sandfly) control and early diagnosis/treatment of cases.

Post-kala-azar Dermal Leishmaniasis (PKDL)

PKDL is a skin condition (hypopigmented macules, papules, nodules) appearing months to years after apparently successful treatment; it is important because these patients act as a reservoir for continued transmission, hindering elimination.

A Note on WHY the Spleen Is So Enormous

• A memorable clinical clue is understanding why kala-azar produces one of the largest spleens in all of medicine.
• The parasite (Leishmania donovani, transmitted by the sandfly) is an obligate intracellular parasite of macrophages.
• It therefore multiplies in the organs richest in macrophages — the reticuloendothelial system: the spleen, the liver, the bone marrow and the lymph nodes.
• The parasitised macrophages proliferate enormously within the spleen, which becomes massively and progressively enlarged — often crossing the midline and reaching the pelvis.
• And that huge spleen has a consequence: hypersplenism — it sequesters and destroys blood cells, producing pancytopenia, which combines with marrow infiltration to give severe anaemia, leucopenia (hence infections, which are the usual cause of death) and thrombocytopenia (hence bleeding).
• Hence the classic picture: a child from an endemic area (Bihar, Jharkhand, West Bengal, eastern UP) with a prolonged, often double-peaked fever, massive splenomegaly, progressive wasting, pancytopenia and darkening of the skin ('kala-azar' = black fever).
• It is fatal if untreated — but eminently curable with liposomal amphotericin B.