Leishmania

• Old World Leishmania


  • L. tropica
  • L. aethiopica
  • L. major
• New World Leishmania


  • L. mexicana
  • L. amazonensis
  • L. guyanensis
  • L. braziliensis
  • L. chagasi
• Leishmania spp.


  Mastigophora (class)

  
• Vector


  • Sandfly (primarily)
  • Genus Phlebotomus (Old World)
  • Genus Lutzomyia (New World)
• Reservoir Hosts


  • Urban: Dogs, rodents
  • Rural: Rodents
• Other Modes of Transmission


  • Congenital
  • Blood transfusion
  • Contamination of bite wounds
  • Direct contact with contaminated specimens
• Phlebotomus Sandfly


  • Golden, brownish, or gray colored
  • Hairy wings in vertical V-shape at rest
  • 6 extremely long legs
• Amastigote


  Found intracellularly in the human or animal host
• Promastigote


  Found inside the vector
• General Life Cycle of Leishmania

  1. Vector sandfly containing infective Promastigotes bites human host

  2. Promastigotes phagocytized by macrophages and transform into Amastigotes

  3. Infected cells burst releasing Amastigotes

  4. Sandfly ingests Amastigotes from infected host

  5. Amastigotes transform into Promastigotes in sandfly midgut

  6. Promastigotes multiply and migrate to proboscis

  7. Sandfly bites another host and infects with Promastigotes

  
• Diagnostic stage


  Amastigote in aspirate or biopsy specimen
• Diagnosis is by observation of parasites in aspirates or biopsy specimen

  
• Transmission


  • Majority: Vector-borne
  • Others: congenital, blood transfusion, contamination of bite wounds, direct contact with contaminated specimens
• Cutaneous Leishmaniasis (CL)


  • Most common form
  • Incubation period: two weeks to months
  • Etiologic agents: L. tropica (dry or urban oriental sore), L. major (moist or rural oriental sore), L. mexicana (chiclero ulcer)

  
• Cutaneous Leishmaniasis lesions


  • Oriental Button: erythematous papule or nodule lesion with raised edges and central crater or violaceous ulcer
  • Heals spontaneously (usually), but may lead to scar formation (If NOT treated)
• Diffuse Cutaneous Leishmaniasis (DCL)


  • Etiologic agent: L. aethiopica
  • Lesion: Localized non-ulcerating papule which eventually develop satellite lesions on the face and extremities

  
• Mucocutaneous Leishmaniasis (MCL)


  • Etiologic Agents: L. braziliensis, L. tropica
  • Started as skin lesions that eventually involve mucous membranes of the oral and nasal cavity
  • Presents: Nasal stuffness, epistaxis, and destruction of the nasal septum (Espundia)
  • Progression into the pharynx and larynx may lead to dysphonia, dysphagia and even aspiration pneumonia

  
• Visceral Leishmaniasis (VL)


  • AKA Kala-azar
  • Disseminated parasitosis
  • Incubation period: 2-8 months
  • Etiologic Agents: L. donovani complex (L. donovani, L. chagasi, L. infantum)
  • Early stage: Twice-daily fever spikes (double quotidian) associated with chills
  • Late stage: fever, weakness, loss of appetite, weight loss, abdominal enlargement, and hepatosplenomegaly

  
• Post-kala azar Dermal Leishmaniasis


  • Sequela of visceral leishmaniasis
  • Manifests as cutaneous eruption resulting in hypopigmented macules, malar erythema, nodules, and ulceration

  
• Diagnosis


  1. Demonstration of the AMASTIGOTE in skin scraping, aspirates, and biopsies

  2. Giemsa stain, and H and E stain are used

  3. New World Cutaneous Leishmaniasis: Culture on NNN, Schneider's Medium, or Animal Inoculation: Hamsters

  
• Montenegro Test


  • Leshmanin Skin Test
  • Used to identify exposure to the parasite
  • Positive in CL, MCL
  • Negative in DCL, Kala azar
  • Positive: >5 mm induration after 48 hours

  
• First Line of Treatment


  • Antimony compounds: Sodium stibogluconate, N-methyl-glucamine (meglumine)
  • Side Effects: Abdominal pain, nausea, arthralgia, fatal arrhythmia
• Second Line of Treatment

  • Miltefosine: India (only oral drug for VL)
  • Amphotericin B
  • Pentamidine
  • Topical Paromomycin: CL
  • Side Effects: Abdominal pain, nausea, arthralgia, fatal arrhythmia
• Prevention and Control


  • Use of insect repellants containing DEET and permethrin
  • Insecticide treated clothing
  • Fine-mesh bed nets
  • Regulation of reservoir hosts
  • No available chemoprophylaxis