Leishmaniasis Quiz

Leishmaniasis

• Caused by failure of cell-mediated immunity
• Immunoglobulin antibodies increase only in visceral leishmaniasis

Effect of Temperature

• Species causing cutaneous lesions cannot grow at core body temperature, but visceral species can

Old World Cutaneous Leishmaniasis

• Endemic in Mediterranean region, Turkey, North and West Africa, Middle and South Asia
• Confined to skin, especially face and limbs
• Occasionally extends to mucous membrane of mouth, producing mucocutaneous lesions

Pathogenesis and Clinical Manifestations

• Promastigotes change to amastigotes, which are rapidly phagocytosed by macrophages
• Parasites replicate, cells rupture, and then invade other cells
• Granulomatous reaction leads to formation of:
  • Nodule at site of inoculation, which crusts and then ulcerates
  • Chronic ulcer with elevated, indurated edges
  • Healing gradually in 2-10 months, leaving a depigmented scar with small nodules at the edge
  • Secondary bacterial infection

Leishmania tropica Complex

• Includes L. tropica, L. major, and L. aethiopica
• L. tropica:
  • Geographically distributed in Mediterranean region, Middle East, South Russia, and India
  • Clinically, it causes a painless ulcer with raised margins, usually affecting face and exposed parts of the body

Morphology and Life Cycle

• Amastigotes in vertebrate host (man and animal)
• Promastigote in arthropode vector (sandfly in old world and Lutzomyia in new world)
• Reservoir hosts: rodents, foxes, and dogs

Mode of Infection (Transmission)

• Biological by the bite of vector containing the infective stage (promastigotes)
• Mechanical by direct contact with ulcerating lesions containing amastigotes
• Blood transfusion in visceral leishmaniasis

Immune Response

• Immunity is mainly cellular (not entirely beneficial, can cause granulomas and tissue destruction)
• According to immune system, one of three events occurs:
  • Parasites are killed by immune response, and person becomes immune to reinfection
  • Local infection is established, which persists until immune response eradicates it or is overwhelmed, permitting dissemination
  • Infection metastasizes through blood to viscera (viscerotropic species), oronasal mucosa (mucocutaneous species), or skin

Laboratory Diagnosis

• Leishmanin (Montenegro) I.D. test:
  • Antigen: washed promastigotes solution in 5% phenol on saline
  • Method: intradermal injection of 0.1 ml antigen in forearm à induration after 48 hours
• Identification of species of Leishmania:
  • Isoenzyme analysis
  • PCR

Treatment

• Local (for simple sores):
  • Excision for small facial lesions
  • Curettage under local anesthesia
  • Heat for 39-41°C for many hours for several days
  • Cryotherapy using liquid nitrogen or carbon dioxide snow
  • Drugs: aminosidine (Paromomycin) ointment or Pentavalent antimony (Pentostam) injections in the edge of the ulcer
• Systemic:
  • Pentavalent antimony (Pentostam): 10 mg/Kg I.M. daily for 10 days
  • Amphotericine B (Fungizone)

Control of Leishmaniasis

• Treatment of cases
• Eradication of reservoir animals
• Control of sandfly using insecticides
• Mosquito’s nets and screens
• Use of repellents as citronella oil in endemic areas
• Health education