Basic Reagents for Parasitological Tests - labsstudies

Basic Reagents for Parasitological Tests

Basic Reagents for Parasitological Tests.

 Examinations of parasites in the Laboratory , we should know the basic Reagents for Parasitological tests.

In this article you will learn:

  • Definitions of terms in Parasitological tests: Reagent, Stains, Parasitology ,Parasites, Medical Parasitology, Diagnostic Parasitology
  • Parasite Investigation in the Laboratory
  • Basic reagents and solutions used for parasitological tests
  • The uses, components, advantages and disadvantages of each Reagents for Parasitological Tests

Definitions terms in Parasitological tests.


  • A substance reacting with another substance to produce a chemical reaction such as stains.


  • Reagents which impart color to substances or things in order to make them easier to visualize.
  • Examples of stains include:  Field and Giemsa stains which are used for visualization of haemoparasites. Stains are also used in Bacteriology and Haematology.


  • Parasitology is the study of parasites.

Now, what are parasites?

  • They are Microorganisms which depend on other living organisms to survive.

What are examples of parasites?

  • Plasmodium species, worms like Ascaris lumbricoides specie, Blood Fluke schistosomes species, etc..

Is there any problem associated with parasites to our health?

Yes, Parasites cause number of diseases like Malaria, anemia, amoebiasis, filariasis, sleeping sickness etc..

 Medical Parasitology

  • It is a study of parasites of medical importance.
  • Parasites of medical importance refers to the group of parasites which have health impacts to humans.  Examples includes;
  • Plasmodium species.
  • Intestinal worms like Ascaris specie.
  • Blood flukes like schistosome species.

Diagnostic Parasitology

  • Study on how to investigate parasitic infections and infestations. 

Parasite Investigation in the Laboratory

  • The use of microscope or other magnifying device is important because most of the parasites of cannot be seen by naked eyes.
  • Most parasites need to be stained (colored) first before magnification. The stains enable to identify the parasite correctly.
  • Some parasites need the contrasting solution to be seen properly.
  • So in Parasitology departments stains and solutions are needed to facilitate the diagnosis, that why we must know this Basic Reagents for Parasitological Tests.


Basic reagents and solutions used for parasitological tests.

Basic Solutions needed in Parasitology

Solutions needed in Parasitology:

  • Normal saline: maintains red blood cells.
  • 10% formal saline: This solution is significant as a fixative for stool specimens and tissue.
  • Distilled Water: for dilution of reagents. Also used a pH stabilizer for Field stain in place of pH 7.2 buffer.
  • Absolute Methanol: dissolves the Fuchsin and Methylene blue stain in the Giemsa satin.
  • pH 7.2 Buffer: pH stabilizer for the Field Stains.
  • Glycerol:  dissolves the Fuchsin and Methylene blue stain in the Giemsa stain preparation.


Basic Reagents needed in Parasitology includes;

  • Field stains
  • Giemsa stains
  • Eosin stain
  • Acridine orange solution
  • Iodine solution

Read also: Preparation of Basic Laboratory Reagents and Solutions

The uses, components, advantages and disadvantages of each Reagents 

Field stain

  • Is Romanowsky stain used in help us to visualize blood parasites. Example of blood parasite is Malaria parasite.

Components of Field stain are;

  • Field stain A
  • Field Stain B
  • Field stain A provide pink and Field stain B blue staining to cells in blood.

Advantages of Field stain

  • The significance is to allow malaria and other blood parasites to be seen
  • Inexpensive and easy to use stain that is visible with a simple light microscope
  • It can help to visualize different stages of blood parasites

Blood film stained with Field Stain showing malaria parasites as bluish cytoplasm with dark dots.

 Giemsa stain

  • Another Romanowsky stain used in Laboratory for help visualize blood parasites.

Components of Giemsa stain are;

  • basic Fuchsin
  • Methylene blue stain

This provide pink and blue staining to cells in blood.

Advantage of Giemsa stain

  •  The significance of this stain is to allow malaria and other blood parasites to be seen.
  • This helping to determine the type of microorganism.


  • This stain is that it is more difficult to prepare.
  • Also the staining process of blood may take much longer than the Field Stain.

The Field and Giemsa stains are Romanowsky stains.

Acridine orange stain

  • Acridine orange is a special stain for viewing blood parasites using a fluorescent microscope.
  • Acridine orange is a fluorochrome that stains nucleic acids of parasites and make them easily seen under fluorescence microscope.
  • The stained nucleic acids are easily seen under fluorescent microscope.
  • The DNA fluoresce green and RNA orange-red.
  • It has been recommended for the rapid identification of Trichomonas vaginalis, yeast cells, and clue cells in vaginal smears.
  • It can also be used to detect intracellular gonococci, meningococci, and other bacteria particularly in blood cultures.

Components of Acridine orange stain are;

  • Acridine orange powder
  • glacial acetic acid
  • distilled water.

Advantages of Acridine Orange (AO)

  • It is ideal for the detection of T. vaginalis and yeast cells.

Disadvantages of Acridine Orange

  • It needs a fluorescent microscope, which is expensive.

Results of Acridine orange stain

Iodine Stain

  • It is a weak solution of iodine such as Dobell and O’Connor (diluted Lugol’s).
  • It is recommended for staining protozoan cysts.
  • Iodine solution stain parasite cysts yellow which make them more visible under microscope.
  • It is often used in wet mounts of concentrated faecal material.
  • It is useful for staining glycogen and making nuclei visible in protozoan cysts.
  • Protozoan cysts correctly stained with iodine contained yellow-gold cytoplasm, brown glycogen material, and paler refractile nuclei.


Advantages of Iodine stain

  • The significance is to detect intestinal parasites in stool specimens.
  • This stain is used to color parasite egg components so that they can be better visualized with a microscope.
  • It enables us to see inside cysts and eggs to help determine the type of parasite.

Disadvantage of Using Iodine Stain

  • This stain will kill any live parasite trophozoite forms.
  • Iodine preparations fade quickly when exposed to light.


Eosin stain

  • It is a pink/red stain that stains proteins non-specifically.
  • Eosin is added to fresh stool to detect motile protozoa.
  • This is advantageous to see the trophozoite forms which are motile and distinguish from non-motile forms.
  • This helps to identify the type of parasite.
  • It is not used to stain eggs or cysts.

Advantage of using Eosin Stain

  • Eosin is advantageous to see the living trophozoite forms which are motile and distinguish from non-motile forms. 

Disadvantage of using Eosin Stain

  • It is not so useful for staining the cyst or eggs.



  •  F.J. Baker, R.E. Silverton (2001): Introduction to Medical Laboratory Technology, 7thEdition, Oxford University Press; Oxford, England.
  •  Monica Cheesbrough (1981): Medical Laboratory Manual for Tropical Countries Volume I, 2nd Edition Butterworth & Co. (Publishers) Ltd;
  •  Monica Cheesbrough (2002): District Laboratory Practice in Tropical Countries Part 1 & 2, Cambridge University Press; Cambridge, England.

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