How to Prepare a Slide for a Fecal & WBC

Veterinarians examine feces and blood under magnification to check for disease and parasites.
Veterinarians examine feces and blood under magnification to check for disease and parasites. (Image: Jupiterimages/Brand X Pictures/Getty Images)

In the veterinary field, slide preparation is commonly used for fecal and blood examination. A fecal examination is the microscopic analysis of feces. The test is used when pets have diarrhea, straining or vomiting. Fecal examinations have two parts: a fecal flotation and a direct fecal smear. A fecal flotation is performed to detect microscopic gastrointestinal parasites, such as roundworms, hookworms, whipworms, tapeworms, coccidia and giardia. A direct fecal smear is performed to detect an overgrowth of certain bacteria that live in the gastrointestinal tract. A blood smear is used to look for abnormal blood cells. White blood cells, red blood cells and platelets have unique and telling morphologies with the presence of certain diseases. A trained veterinarian or technician evaluates fecal samples and blood smears for parasites, bacteria and abnormally shaped cells.

Things You'll Need

  • Fecal flotation container
  • Fecal flotation solution
  • Coverslips
  • Microscope slides
  • Lighter
  • Gram stain supplies
  • Paper towel
  • Microscope
  • Hematocrit tube
  • Diff-Quick supplies

Fecal Flotation

Obtain a fecal sample. Pet owners can bring in a sample or a sample can be obtained by inserting a fecal loop 1 to 3 inches into the rectum, depending on the pet’s size.

Place the fecal material into a fecal container. These containers are available commercially and look like a test tube or sample vial.

Fill the fecal container with flotation solution about halfway and agitate the fecal loop. The fecal material will break up. Get as much material as possible off the fecal loop (if one was used). Once the material is broken up, fill the fecal container to the very top with flotation solution.

Place a coverslip over the top of the container and wait 10 minutes before continuing. Parasite ovum will float to the top and stick to the coverslip.

Place the coverslip and any adhered material onto a microscope slide. Any adhered material should be between the coverslip and the microscope slide. The slide is ready for microscopic analysis.

Direct Fecal Smear

Obtain a small amount of fecal matter. The amount required is about half the volume of a dime.

Spread the fecal matter thinly on a microscope slide. The material should evenly cover the slide. Another microscope slide is often used to facilitate the spreading.

Fix the slide’s contents with a lighter. Gently heating the clean side of the slide for 5 to 10 seconds dries all the material on the slide and binds the sample to the glass.

Stain the slide using gram-staining protocols.

Wait for the slide to dry. The slide should be placed on end with a paper towel underneath to wick away excess staining material. The slide takes approximately 15 minutes to dry. Once dry, the slide is ready for analysis.

Blood Smear

Obtain a peripheral blood sample from the pet. This can only be done at a veterinarian’s office. A peripheral blood sample comes from a leg vein. Place the blood in a non-clotting blood sample tube filled with heparin or EDTA.

Remove a small sample of blood from the non-clotting blood sample tube using a needle and syringe. Inject a small amount of this into a hematocrit tube. Place a drop of blood from the hematocrit tube onto a slide.

Spread the drop by using another microscope slide. This second slide should be angled 45 degrees from the first slide: if the slides were clock hands, the time would be 10:15. In this metaphor, the “hour” slide is the second, angled slide, while the “minute” slide contains the blood sample. Push the “minute” slide across the surface of the “hour” slide. This pulls the blood across to make the smear.

Wait 5 to 10 minutes for the slide to air dry.

Stain the slide in Diff-Quick stain. Let the slide dry for 5 to 10 minutes. Place the slide end-on with a paper towel underneath to wick away any excess stain. The slide is ready to be analyzed.

Tips & Warnings

  • When spreading the blood smear, spreading slowly ensures an even smear.
  • Wear gloves when handling specimens to avoid accidental zoonotic infection.
  • Only trained professionals should perform these tests.

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