Parasitic protozoa e vacuole ectoplasm ntamoeba histolytica

Дата канвертавання25.04.2016
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Parasitic protozoa

Parasitic protozoa

ntamoeba histolytica
is one of a number


f species of small amoebae which live in the

alimentary canal of humans. These are usually

harmless protozoa, feeding on bacteria and


articles in the intestine. In certain conditions,

entamoeba invades the wall of the intestine or

rectum causing ulceration and bleeding, with

pain, vomiting and diarrhoea, symptoms of

moebic dysentery. The faeces of infected


eople contain resistant forms (cysts) of

Entamoeba histolytica

ntamoeba. Conditions of poor sanitation and

hygiene, therefore, favour the spread of the disease.

Trypanosomes are flagellate protozoa which live in the blood stream. There are several different species of trypanosome and they cause diseases such as sleeping sickness, leishmaniasis and Chaga's disease and, in cattle, nagana. The sleeping sickness and nagana parasites are transmitted by the bite of the tsetse fly. This insect has tubular mouthparts, like the mosquito, and these pierce the skin to suck blood from a capillary. If the tetse fly bites an infected person, it sucks up the trypanosomes with the blood. The trypanosomes multiply in the body of the tsetse fly and invade the salivary glands. When the fly bites a healthy person, it injects saliva, which contains the trypanosomes.

The prevalence of tsetse flies in some areas makes it impossible to raise cattle because of the high incidence of nagana.

The main methods of control involve attempts to reduce the population of tsetse flies. This is done by using insecticides or by changing or removing the vegetation from the areas where the tsetse flies breed. These methods are only partially successful; spraying from the air, for example, is ineffective if the flies are resting on the underside of leaves.

red cell



new flagellum forming

Trypanosomes in the blood

Trypanosome reproducing

by binary fission

© D.G. Mackean

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