TRYPANOSOMES AND LEISHMANIAL ORGANISMS

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TRYPANOSOMES AND LEISHMANIAL ORGANISMS

 

The trypanosomes and leishmanial organims all have a flagellum (or undulipodium of some workers) in some part of their life cycle that is connected to a large mitochondrial body that was called a kinetosome or a kineto plast by early microscopists. It is the presence of this structure that causes these parasites to be grouped with other organisms within the phylum Kinetoplastida. Some members of the Kinetoplastida are parasites of invertebrates only, others are parasites of invertebrates, as well as, plants and animals. One group of these organisms that is parasitic in mammals has a single stage in the vertebrate host, an elongate cell called the trypomastigote. The trypomastigote has a large nucleus and a long flagellum that runs the length of the body from the posterior to the anterior end where there is typically a free portion. Along the body, the flagellum is attached to the cell body of the parasite by a thin later of cell membranes and cytoplasm; this is what produces the strucute called the “undulating membrane” (so called , because as the flagellum beats, the membrane undulates). In cats, the members of the genus Trypanosoma that are transmitted by the bites of flies or bugs, Trypanosomabrucei, Trypanosomagambiense, Trypanosomacongolense, Trypansomaevansi, and Trypanosomarangeli, are members of this first group. A second group is represented by the members of the genus Leishmania. In this group, the only stage found in the tissues of the vertebrate host is a round, intracellular form that consists of a nucleus and the large kinetoplast. The members of this genus are transmitted by the bite of a phlebotomine sandfly, where the flagellated form of this parasite is found. The third group of Kinetoplastid parasites found in cats is represented by Trypanosoma cruzi. This is a diphasic organism that has a a stage in tissues of its vertebrate host which is similar to the amastigote stage of the Leishmania parasites and a trypomastigote stage which is present in the blood of the vertebrate host during the acute phase of the infection. Trypanosomacruzi is transmitted in the feces of a kissing or triatomid bug.

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