Introduction
Leishmania is a kinetoplastid flagellate, like the trypanosomes (topic 78), but its life in man is the opposite of theirs: it lives inside macrophages as an amastigote and is carried by sandflies. About 20 species infect humans and cause the leishmaniases: cutaneous, mucocutaneous and visceral disease. They affect around 1 million people a year in about 90 countries, and visceral leishmaniasis also occurs in Bulgaria.
Systematic position
- Kingdom Protista (Protozoa) → Phylum Sarcomastigophora → Subphylum Mastigophora → Class Zoomastigophorea → Order Kinetoplastida → Family Trypanosomatidae → Genus Leishmania.
- Two subgenera: Leishmania (Old and New World species) and Viannia (New World species that develop in the sandfly's hindgut, e.g. L. (V.) braziliensis).
- Named after William Leishman and Charles Donovan, who described the amastigotes in 1903; amastigotes in tissue are still called Leishman–Donovan (LD) bodies.
Morphology: two forms
Amastigotes (Leishman–Donovan bodies) of L. donovani: tiny oval bodies, each with a nucleus and a dark rod-shaped kinetoplast, packed in macrophages.
Image: “Leishmania donovani amastigotes in Giemsa stained smear of FNAC” by Ajay Kumar Chaurasiya, CC BY-SA 4.0, via Wikimedia Commons.
Promastigotes of L. major from culture: slender, with the kinetoplast and the free flagellum at the front.
Image: “Leishmania major promastigotes” by Original uploader was Abanima at ru.wikipedia, CC BY-SA 3.0, via Wikimedia Commons.