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In this article we will discuss about:- 1. Habitat of Leishmania Donovani 2. Morphology of Leishmania Donovani 3. Life-Cycle.
Habitat of Leishmania Donovani:
Leishmania donovani like Trypanosoma is a haeomoflagellate parasite. In man it resides in Leishmanial form in lymphoid—macrophage (Reticuloendothelial) cells of the spleen, liver, bone- marrow, intestine and lymph glands.
In its vector host Sand fly, Phlebotomous it is found in Leptomonad form in the intestine. The disease caused by leishmania is known as Leishmaniasis or Kala-azar. The disease is prevalent in the Eastern hemisphere specially in India, Southern U.S.S.R., Burma, Central China, Iraq etc.
Morphology of Leishmania Donovani:
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In man the intracellular parasite occurs as Leishmanial forms. These are oval or spherical in shape and measure 2-4 micra by 1·5-2 micra. The flagallum is absent. Nucleus and kenetoplast are well formed. The kinetoplast is elongated and lie perpendicular or tangential to the nucleus.
An axoneme ranging between the kinetoplast and periplast may remain present. In the intermediate host the parasite occurs as Leptomonad forms. The leptomonad forms are long, slender measuring 7-20 micron. It has a long flagellum (Fig. 50E).
Life-Cycle of Leishmania Donovani:
In man the intracellular parasites undergo repeated binary fission resulting over crowdedness inside the host cell. The host cell ultimately bursts and parasites are released. The fly ingests Leishmanias along with the blood of man.
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The parasites after reaching the midgut of the fly increase in size, develop flagellum and becomes metamorphosed into leptomonad form. The leptomonads multiply by longitudinal binary fission and reach the proventriculus of the fly.
Repeated multiplication inside the proventriculus causes complete obstruction of the organ. In this condition when the fly tries to ingest fresh blood, the meal can go no further than the oesophagus. This causes a regurgitation of the sucked blood during bite. Along with the regurgitated blood leptomonad forms are introduced in the blood stream of man.
