Leishmania donovani

 

Leishmania donovani: Life Cycle, Pathogenesis, Treatment Prevention and Diagnosis

 

Leishmania donovani: The Causative Agent of Kalaazar (Visceral Leishmaniasis)

Lifecycle

 Reservoir Hosts: Various mammals (e.g., dogs, foxes, rodents).

 Vector: Female sandflies.

   Require blood meals for egg maturation.

   Ingest macrophages containing amastigotes when feeding on an infected host.

Inside the Sandfly:

1. Amastigotes transform into promastigotes in the gut.

2. Promastigotes multiply and migrate to the pharynx and proboscis.

3. This process takes about 10 days.

Transmission to Humans:

1. Sandfly bites human, injecting promastigotes.

2. Promastigotes are engulfed by macrophages.

3. Inside macrophages, promastigotes transform back into amastigotes.

Within the Human Host:

1. Amastigotes evade destruction by preventing vacuolelysosome fusion.

2. Infect other macrophages and reticuloendothelial cells.

Cycle Completion:

 Another sandfly ingests macrophages containing amastigotes during feeding.

Laboratory Diagnosis

 Detection: Amastigotes in bone marrow, spleen, or lymph node biopsies/touch preparations.

 Tests:

   Cultures and serologic tests (indirect immunofluorescence) usually positive.

   High IgG levels indicate infection but are not diagnostic.

   Skin test (leishmanin):

     Negative during active disease.

     Positive in recovered patients.

Treatment & Prevention

 Drugs of Choice:

   Liposomal amphotericin B

   Sodium stibogluconate

 Treatment Outcomes:

   Reduces mortality rate to nearly 5%

   Recovery confers permanent immunity

 Prevention:

   Avoid sandfly bites

   Use netting

   Wear protective clothing

   Apply insect repellents

   Conduct insecticide spraying.