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Leishmania donovani - Life Cycle, Epidemiology, Reservoir, Transmission, Treatment, Prevention, Control

Last Modified: December 15, 2022

Life Cycle of Leishmania donovani

The life cycle of Leishmania donovani is completed in two different hosts:

  • Man or other mammals- the amastigote form

  • Sandfly of genus Phlebotomus and Lutzomyia – the promastigote form

These mammals include dogs, rodents, foxes, etc.

  • Leishmania donovani is transmitted to man and other vertebrates by the bite of a blood-sucking female sandfly

  • During the blood meal, the promastigotes are transmitted from the saliva of the vector to the host’s skin

  • the promastigotes are then immediately phagocytosed by the host macrophages where they transform into amastigotes

  • the newly formed Leishmania donovani amastigotes undergo binary fission to produce a large number of amastigotes which continue to divide inside the enlarged macrophages

  • the infected macrophages rupture to release a large number of amastigotes (around 200 in number) into the host body circulation

  • the parasites then invade the monocytes of the blood, macrophages of the spleen, liver, bone marrow, lymph nodes as well as other tissues of the reticuloendothelial cells

  • if the infected mammal host (including man) is bitten by a female sand-fly during a blood meal, the free amastigotes are also taken up with the host blood

  • in the midgut of the sand-fly, within 72 hours, the Leishmania donovani amastigotes are transformed into promastigotes

  • the morphological transformation takes place through a series of flagellated intermediate promastigote forms to flagellated promastigotes

  • the promastigotes undergo binary fission, produce a large number of parasites, and completely fill the lumen of the gut

  • after 6-9 days, the promastigotes travel to the sandfly's pharynx and buccal cavity from the mid-gut

  • bite from the infected sand-fly to mammals (including humans) during its blood meal transmits the infection and the life cycle of Leishmania donovani is continued

Figure: L. donovani life cycle (Source: CDC)

Epidemiology of Leishmania donovani

  • Epidemiologically, Leishmania donovani is found in 88 countries (16 industrialized and 72 developing countries)

  • the continents Australia and Antarctica are free of leishmaniasis while Asia, Africa, South America, North America, and Europe have recorded cases of leishmaniasis to varying degrees

Reservoir, Source of Leishmania donovani

The reservoir of Leishmania donovani depends upon the area of the globe where the infection is occurring.

  • In India, only human-sandfly transmission occurs and humans are the only reservoir

  • rodents are reservoirs of Leishmania donovani in Africa

  • foxes are reservoirs of Leishmania donovani in Brazil and Central Asia

  • canines reservoirs of Leishmania donovani in China and the Mediterranean

Transmission of Leishmania donovani

  • occurs mainly by the bite of vector i.e. sand-fly (Phlebotomus argentipes)

  • less frequently, Leishmania donovani transmission occurs via

    blood transfusion

    congenital infection

    unprotected sexual intercourse

    accidental infection in a laboratory setting

Treatment of Leishmania donovani

The treatment of leishmaniasis, caused by Leishmania donovani, includes

  • specific therapy supplemented with the treatment of secondary infections

  • high-calorie diet

  • blood transfusion in cases of severe anemia

Drugs used include:

  • Pentavalent antimonials

    megalumine antimonate

    sodium stibugluconate solution

  • Pentamidine

    pentamidine isethionate

    pentamidine dimethane

  • Amphotericin B

  • Miltefosine

  • Interferon

Prevention, Control of Leishmania donovani

The prevention, control of Leishmania donovani can be done as:

  • reduction of sand-fly population by using insecticides

  • evade contact with potential animal vectors such as dogs, foxes, and rodents

  • use of bed nets, window nets, or insect repellents

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