Describe the clinical features, diagnosis and treatment of Kala-azar.

Clinical Features

Kala-azar typically presents with a gradual onset of symptoms, often making early diagnosis difficult. The disease progresses through several stages:

• Initial Stage (Febrile Stage): Characterized by prolonged, intermittent fever (often biphasic – rising and falling), chills, malaise, and weight loss. This stage can last for weeks to months.
• Hepatosplenomegaly Stage: Progressive enlargement of the spleen and liver is the hallmark of this stage. The spleen becomes massively enlarged, often palpable several centimeters below the costal margin. Hepatomegaly is also present, though usually less pronounced than splenomegaly.
• Advanced Stage: This stage is marked by severe anemia, pancytopenia (reduction in all blood cell counts), hypergammaglobulinemia, and cachexia (extreme wasting). Patients may develop jaundice, edema, and bleeding tendencies. Darkening of the skin (hence the name "Kala-azar" – black fever) can occur, particularly in individuals with darker skin tones.

Other clinical features include:

• Post-kala-azar dermal leishmaniasis (PKDL): A characteristic skin manifestation that can develop months or years after apparent recovery from VL.
• Lymphadenopathy: Enlargement of lymph nodes may occur.
• Epistaxis: Nosebleeds due to thrombocytopenia.

Diagnosis

Diagnosis of Kala-azar requires a combination of clinical suspicion and laboratory confirmation. Several diagnostic tests are available:

• Parasitological Tests:
  • Microscopic Examination: Aspiration of bone marrow, spleen, or lymph node followed by microscopic examination for the presence of amastigotes (intracellular parasites). This is the gold standard but has limited sensitivity.
  • Culture: Culturing samples (bone marrow, spleen) on specialized media (e.g., Novy-MacNeal-Nicolle – NNN medium) allows for parasite isolation and identification.
  • Direct Agglutination Test (DAT): A serological test detecting antibodies against *Leishmania donovani*. High sensitivity but lower specificity.
• Immunological Tests:
  • rK39 Dipstick Test: A rapid, point-of-care diagnostic test detecting antibodies against a recombinant *Leishmania* antigen (rK39). High sensitivity and specificity, widely used in endemic areas.
  • Enzyme-Linked Immunosorbent Assay (ELISA): Detects antibodies against *Leishmania* antigens.
• Molecular Tests:
  • Polymerase Chain Reaction (PCR): Highly sensitive and specific for detecting *Leishmania* DNA in samples. Useful for confirming diagnosis and monitoring treatment response.

Treatment

Treatment of Kala-azar aims to eliminate the parasite and alleviate symptoms. The treatment regimen depends on the severity of the disease, patient’s age, and co-morbidities.

• First-line Treatment:
  • Liposomal Amphotericin B (L-AmB): Considered the most effective and safest treatment option. Administered intravenously over several days.
• Second-line Treatments:
  • Miltefosine: An oral drug effective against VL, but has potential teratogenic effects and should not be used in pregnant women.
  • Amphotericin B Deoxycholate (AmB-d): Less well-tolerated than L-AmB due to its nephrotoxicity. Requires careful monitoring.
  • Sodium Stibogluconate (SSG): Historically used, but associated with significant side effects (cardiotoxicity, pancreatitis). Its use is declining.
• Post-Treatment Follow-up: Patients require regular follow-up to monitor for relapse and PKDL.

Treatment of PKDL typically involves topical or systemic antileishmanial drugs, such as miltefosine or SSG.