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Identification of protozoan parasites. Virtual Lab

Plasmodium falciparum
Plasmodium falciparum, protozoan that causes malaria in humans
Some of the protozoa, these microscopic protists, who share characteristics of plants and animals and live in water, are a serious problem for human and animal health, since many of them are parasites and cause very serious diseases.

According to the World Health Organization (WHO), in the year 2015 there were about 214,000,000 cases of malaria, a disease caused by the protozoan Plasmodium, which killed 438,000 people. Leishmaniasis, caused by the protozoan Leishmania is a disease that affects dogs and humans, causes severe ulcers on the skin leaving scars for life. The trichomoniasis, a sexually transmitted disease, is caused by the protozoan Trichomonas vaginalis. Some sources estimate an incidence of 70% in populations of developed countries, with no symptoms or sporadic symptoms such as itching or pain in sexual intercourse. These are just some examples of the importance of parasites in human health. And this without mentioning the importance in animal health, both in the animals that surround us, and in the livestock economy.

The identification of the parasite is fundamental for the correct diagnosis of the parasitosis. This requires a training in microscopic staining and identification techniques, and in some cases additional tests, such as the ELISA test.


- Reading: Austin Community College. Medical Parasitology. Lab Manual ( LABORATORY EXERCISE 3:  Identification of Parasites)


Microscopic identification techniques for protozoan parasites are complex and require specialized training.

This experiment will focus, not on the manipulation of the samples, nor on the microscopic techniques of preparation and staining, but on the identification of protozoan parasites through microscopic observation. For this, a series of intestinal protozoan parasites will be observed under the microscope.

- Reading: M. Arcari, A. Baxendine and C. E. Bennett. Diagnosing Medical Parasites Through Coprological Techniques: Volume 1 The Amoebae  See BelowVolume 2. The Ciliates, Coccidia and MicrosporidiaVolume 3. The Flagellates

Ways to perform the experiment

1. In Laboratory

The laboratory that performs experiments and tests of parasitic protozoology, must have a supply of samples, adequate instruments and staff training. If this is not possible, microscopy preparations can be acquired. One microscopy preparation of parasitic protozoa usually cost about 8-10 $.

2. In Home Lab

In principle, the experiment is not dangerous if carried out with commercial microscopic preparations. For the experiment it is necessary to have a microscope something better than a toy. There are possibilities for setting up a low cost home microscopy lab (in spanish).

3. Virtually

For this purpose, microscopic images of parasitic protozoa can be made in the same post in the next section.

Microscopic images of protozoan parasites

Click on the image to enlarge.

Entamoeba histolytica
Entamoeba histolytica

Trichomonas vaginales (tinción Giemsa)
Trichomonas vaginalis

Tripanosoma cruzi
Tripanosoma cruzi

Plasmodium falciparum
Plasmodium falciparum

Toxoplasma gondii
Toxoplasma gondii

Leishmania donovani
Leishmania donovani in bone marrow cells (in the center)


Giardia lamblia

Pentatrichomonas hominis, fresh analysis of human feces

Trichomonas vaginalis, thawed after freezing

Questions and activities

1.- Draw the observed protozoa.

2.- Make a table or diagram of identification of the observed protozoa.

3.- Indicate the identifying characters of each protozoan observed, a small description and their parasitological importance.

4.- Search the Internet for images of protozoan parasites.

5.- Enter into the website Protist Image Data, access the database of protists, identify protozoan parasites and access their images and data (the website has some years and there are several broken links).

Resources for further learning

- Reading: World Health Organization. Basic laboratory methods in medical parasitology (pdf)

Spanish version of this page


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