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Questions and Answers
What is the primary mechanism of transmission for Leishmania parasites?
What is the primary mechanism of transmission for Leishmania parasites?
What is the correlation between the leishmanin skin test and the progression of leishmaniasis?
What is the correlation between the leishmanin skin test and the progression of leishmaniasis?
What is the primary immune response responsible for defense against Leishmania?
What is the primary immune response responsible for defense against Leishmania?
Which species of Leishmania is commonly associated with mucosal leishmaniasis in the New World?
Which species of Leishmania is commonly associated with mucosal leishmaniasis in the New World?
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What is the typical duration of infectivity in sandflies that transmit Leishmania?
What is the typical duration of infectivity in sandflies that transmit Leishmania?
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What is the primary mechanism by which promastigotes are introduced into a vertebrate host?
What is the primary mechanism by which promastigotes are introduced into a vertebrate host?
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What is the characteristic shape of amastigotes?
What is the characteristic shape of amastigotes?
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Which of the following is a characteristic of visceral leishmaniasis?
Which of the following is a characteristic of visceral leishmaniasis?
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What is the primary site of amastigote multiplication?
What is the primary site of amastigote multiplication?
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Which species complex of Leishmania parasites is typically associated with visceral leishmaniasis?
Which species complex of Leishmania parasites is typically associated with visceral leishmaniasis?
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Study Notes
Leishmaniasis
- Caused by protozoan parasites of the genus Leishmania, transmitted by sandflies of the genera Phlebotomus (Old World) and Lutzomyia (New World)
- Results in diverse group of cutaneous and visceral clinical syndromes
Life Cycle
- Promastigotes in the female sandfly are introduced into the skin of a vertebrate host during a blood meal
- Promastigotes invade reticuloendothelial cells, transform into amastigotes (2-5 μm in diameter) within reticuloendothelial cells
- Amastigotes multiply within phagolysosomes, invade other reticuloendothelial cells
- Sandflies feeding on infected individuals ingest parasitized cells, amastigotes transform into promastigotes, multiply in the gut, and migrate to the proboscis, completing the cycle
Clinical Classification
- Separates into three major syndromes: visceral leishmaniasis, cutaneous leishmaniasis, and mucosal leishmaniasis
- Visceral leishmaniasis: fever, wasting, pancytopenia, hepatosplenomegaly, and hypergammaglobulinemia
- Cutaneous leishmaniasis: localized, nonhealing ulcerative skin lesion
- Mucosal leishmaniasis: primary cutaneous lesion followed by destructive nasopharyngeal lesions (espundia)
Transmission and Epidemiology
- Sandflies are inactive in daylight, seeking shelter in dark, moist places
- Female sandflies feed on various warm- and cold-blooded hosts, acquiring Leishmania with their first blood meal
- They can transmit disease 7-10 days later and remain infective throughout adult life
- Other routes of transmission: blood transfusion, needle-sharing, congenital transmission, sexual contact, and laboratory accidents
Immunology
- Protective immune response is primarily cell-mediated
- High titers of antibodies in visceral leishmaniasis play no part in defense against the parasite
- Positive leishmanin skin test correlates with resistance to leishmaniasis
- Cell-mediated immunity (CMI) causes tissue destruction and correlates with the onset of ulceration in cutaneous leishmaniasis
Visceral Leishmaniasis
- Most often caused by species of the L. donovani complex: Leishmania donovani and Leishmania infantum
- Transmitted by phlebotomine sandflies of the genera Phlebotomus (Old World) and Lutzomyia (New World)
- Regional epidemiology depends on the interaction of sandflies, reservoir hosts, and susceptible humans
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Description
Learn about the biology and life cycle of Leishmania parasites, transmitted by sandflies, and their role in causing diverse clinical syndromes. Understand the different stages of the parasite's life cycle and how it affects vertebrate hosts.
