Focus on pathogens: Leishmania species

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Focus on pathogens Leishmania species

• Facts / life-cycle Several species of Leishmania
  (another hemoflagellate) cause human disease.
  The organism is transmitted via regurgitation of
  promastigote Leishmania larvae from the gut and
  pharynx of sand flies when they take blood meals.
  Dogs, rodents, and other endemic animals (such
  as sloths marsupials of S. America) also serve
  as DH.
• Leismaniasis has 2 forms. Visceral (VL),
  commonly caused by L. donovani, is a disseminated
  disease involving organs and tissues of the GI
  and reticuloendothelial systems. The cutaneous
  (CL) form results in ulcers or sores on skin and
  mucous membranes. The cutaneous form is less
  severe in regard to loss of life, but is
  significant as you will see.
• Life-cycles are thought to be similar for all
  species.

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Focus on pathogens Epidemiology

• Both types of Leishmaniasis are distributed
  worldwide. S. America, especially Brazil is the
  1 hotspot for both types. Other endemic areas
  include the Meditteranean rim, the Middle East,
  India, and scattered in Africa. Both affect
  mainly children and the immune suppressed.
• Cutaneous Approx. 300,000 new cases of CL are
  reported annually from an at-risk population of
  200 million. Epidemics of CL frequently occur
  when a nonimmune population intrudes into a
  natural enzootic cycle. The population at highest
  risk for CL is nonimmune expatriates such as
  tourists, soldiers, new settlers, and
  construction or agricultural workers
• Visceral 12 million cases with 400,000 new cases
  per year. Mortality rates are reported to be
  25. Both vaccine and antimicrobial outlooks
  are poor.

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Focus on pathogens pathology / clinical symptoms

• Cutaneous
• Small, roughly circular lesions form at site of
  entry, most often of facial extremities or hands,
  but can be anywhere on the skin. The lesions
  have flattened ulcerative centers with raised
  satelite papules. Lesions usually expand
  chronically and radially from the initial wound,
  but sometimes spread over a larger area (oral,
  phayngeal, nasal). Some texts distinguish this
  latter pathology clinical behavior as
  mucocutaneous Leishmanisis. Lesions are
  sometimes self limiting. Gross tissue damage
  results in severe scaring and malformation.

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Focus on pathogens pathology / clinical symptoms

• Visceral Leishmaniasis also called kala-azar,
  dumdum fever
• symptoms of course depend upon affected organs /
  tissues
• rarely is there a visible local lesion at site
  of bite
• thickening, stiffening darkening of eyebrows
  lashes
• 1-2months following infection, there begins a
  daily fever with rise to 102-104oF
• hepatosplenomegaly
• jaudice due to liver dysfunction
• skin develops hyperpigmented granulomatous spots
  (kala-azar means black disease)
• death in 25 of cases due to secondary
  infection or other complications

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Focus on pathogens Leishmania species

• Laboratory diagnosis species causing CL VL
  cannot be distinguished microscopically.
  Therefore, it is important to use clinical
  symptoms and serology as supporting evidence.
  Samples examined include blood, CL lesion fluid,
  biopsies.
• Amastigote oval, 2-5 microns by 1 - 3 microns.
  Most likely seen inside macrophages.
• Promastigote rarely seen in clinical samples,
  most likely recovered from gut of IH 14 - 20
  microns by 1.5 - 4 microns, similar in size
  appearance to trypanosomes

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L. donovani amastigotes in macrophages
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Leishmania promastigotes