In this article we will discuss about the structure of haemoflagellates or Leishmania Donovani. This will also help you draw the diagram and structure of haemoflagellates.

The genus Leishmania occurs only in two different forms or stages:

(a) Amastigote form also known as “Leishman Donovan Body” occurring in vertebrates including man; and

(b) Pro-mastigote form called the leptomonad occurring in the sand-fly.

(a) Amastigote form (Aflagellar stage):

The parasite at this stage resides in the cells of the reticulo-endothelial system of vertebrate hosts (man, dog, hamster).

Leishmania tropica and L. donovani

The characteristics of the amastigote form are as follows:

1. Shape and size:

It is a round or oval body measuring 2-4 μm along the longi­tudinal axis.

2. Cell membrane is delicate.

3. Nucleus is oval or round in shape and is usually situated in the middle of the cells or along the side of the cell membrane.

4. Kinetoplast lies tangentially or at right angles to the nucleus. It is provided with a DNA containing body and a mitochon­drial body.

5. Axoneme is a delicate filament exten­ding from the kinetoplast to the margin of the body. It represents the root of the flagellum (Fig. 3.2).

  A. Amastigote and leishmanial form, B. Promastigote or leptomonad form

6. Vacuole is a clear unstained space lying along-side the axoneme.

(b) Pro-mastigote form (flagellar stage):

This stage of the parasite is encountered in the midgut of the invertebrate host or sand-fly.

1. Shape and size:

The parasite is elonga­ted, slender and spindle shaped. A fully formed promastigote stage measures 15-20 μm in length and 1-2 μm in breadth.

2. Cell membrane:

The whole body is cov­ered externally by a very thin, delicate, elastic and firm covering.

3. Nucleus:

A single large spherical nucleus lies eccentrically or in the middle of the body.

4. Cytoplasm:

Underneath cell membrane the cytoplasm is colourless, homo­geneous and not differentiated into ecto­plasm and endoplasm. Under E.M the cytoplasm is marked by longitudinal striations or microtubules.

Other struc­tures found in the cytoplasm are the kinetoplast, rhizoplast, Golgi-body, mito­chondria, eosinophilic vacuole etc. Kinetoplast lies transversely near the anterior end. Eosinophilic vacuole, a light staining area lying in front of the kinetoplast over which the root of the flagellum runs.

Flagellum:

It may be of the same length as the body or even longer, projecting from the front and the flagellum does not curve round the body of the parasite.

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