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4. Parasitology 117
Rapid Field stain for faecal trophozoites
Materials and reagents
● Microscope
● Microscope slides
● Slide rack
● Field stain (reagent no. 25):
— Field stain A (undiluted)
— Field stain B (diluted one part of stain in four parts of distilled water)
● Sodium chloride, 0.85% solution (reagent no. 53)
●
Methanol.
Method
1. Prepare a thin faecal smear in sodium chloride solution on a clean slide.
2. Once the smear is dry, fix it by covering the slide with methanol for 3
minutes.
3. Tip off the methanol.
4. Pipette 1ml of diluted Field stain B onto the slide, followed by 1ml of
undiluted Field stain A.
5. Mix well by tilting the slide and allow to stain for 1 minute.
6. Wash the slide in water and allow it to air-dry.
7. Examine the slide using the ¥100 oil-immersion objective. Scan the smear,
particularly around the edges.
The cytoplasm and flagella of trophozoites of Giardia intestinalis stain blue
and their nuclei stain red. Cysts of G. intestinalis also stain blue and their
nuclei stain red.
Note:
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Leave freshly prepared stains for 3 days before use.
Use rainwater to prepare the stains if the local well-water supply is too salty.
Cover the jars containing the staining solutions to prevent evaporation and
absorption of dust.
Avoid carrying over one staining solution to another.
Fig. 4.23 Balantidium coli trophozoite
Eosin stain for faecal trophozoites and cysts
Materials and reagents
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Microscope
Microscope slides
Slide rack
Coverslips
● Eosin, 1% solution (reagent no. 23).
Method
1. Emulsify a small portion of stool in 1% eosin solution on a clean slide. Spread
over an area of approximately 2cm ¥ 1cm.
2. Put a coverslip on the slide and place it on the microscope stage.
3. Use the ¥10 objective to examine the smear systematically for unstained
trophozoites and cysts. Examine in more detail with the ¥40 objective.