Leishmania

Overview
  • Leishmania refer to a genus of flagellated protozoa which are transmitted by arthropod vector and can infect a wide variety of mammals. Infection with leishmania can manifest as a number of clinical distinct syndromes.
Life Cycle
  • Humans are inoculated during blood meals by Sandflies which have previously bitten infected animals. The inoculating form of the organism is the motile "Promastigote" which is phagocytosed by local macrophages. Inside the macrophage phagosome, the organism transforms into the immotile "Amastigote" form and proceeds to replicate, eventually causing lysis of the cell only to be phagocytosed by fresh macrophages. Additionally, infected macrophages disseminate the organism widely throughout a variety of tissues.
Clinical Consequences
  • Overview
    • Infection with leishmania can manifest as one of three basic syndromes. The host immune response, along with immunomodulatory properties of the particular infecting leishmania species likely determine how infection will manifest.
  • Cutaneous Leishmaniasis
    • Cutaneous Leishmaniasis manifests as the localized development of a skin lesion at the site of sandfly inoculation. The active lesion, which is papulonodular and often possess a central ulceration, may last for up to a year before a successful immune response eliminates the organism and causes the lesion to scar over. Some species of leishmania appear to modulate immunity to avoid a successful immune response resulting in "Diffuse Cutaneous Leishmaniasis" which manifests as the chronic presence of multiple cutaneous lesions over the entire body which do not ulcerate.
  • Mucosal Leishmaniasis
    • In some individuals, cutaneous infection progresses to involvement of the nasopharynx and oral cavity. Signs usually appear more than a year after the cutaneous lesion has healed and manifest as ulcerations of the nasopharyngeal mucosa or oral mucosa. Over time, the basic architecture of the nose and mouth can become severely eroded due to chronic ulceration.
  • Visceral Leishmaniasis
    • Visceral Leishmaniasis, also known as "Kala-azar" is characterized by dramatic splenomegaly along with some hepatomegaly, causing distention of the abdomen. Fever and weight loss are common along with derangement of blood components such as anemia, leukopenia, and thrombocytopenia.
Treatment
  • Treatment of Leishmaniasis is traditionally with Sodium Stibogluconate.