The Arizona STEM Acceleration Project

Eggs Afloat

Eggs Afloat

A 9-12th grade STEM lesson

Victoria Imhoff

Date: January 25th, 2024

Notes for teachers

• This lesson takes place in a laboratory classroom over one BLOCK class period.
• Students may work in small groups of 2-4.
• Identify a group leader to maintain lab space and supplies.
• Facilitate student reflection on analysis and conclusion questions as the assessment.

List of Materials (Per Group)

Per team of three students:

• Agricultural parasites slide set
• Microscope
• Dilute iodine solution
• Distilled water
• Flotation solution
• Cheesecloth
• 3 microscope slides and coverslips
• 2 toothpicks
• Test tube
• Test tube rack
• Paper funnel
• Medicine cup
• Forceps
• Pipette

Per class:

• Internal animal parasites poster
• Assorted fecal samples
• Electronic balance

Per pair of students:

• Disposable gloves
• Lab apron
• Safety glasses
• Pencil
• Journal

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Science Standards

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AgriScience Standards

Animal Systems Career Pathway (AG-ANI)

5. Evaluate environmental factors affecting animal performance and implement procedures for enhancing performance and animal health.

• AG-ANI 5.1: Reduce or mitigate the environmental impacts of animal management or production.

Career Ready Practices

7. Employ valid and reliable research strategies.

• CRP.07.01: Select and implement reliable research processes and methods to generate data for decision-making in the workplace and community.

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Objective:

Students will be able to prepare slides and observe to determine the presence of parasite eggs.

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Agenda (55 minutes, 1 Class Period)

Bellwork Question: How can you determine if an animal has internal parasites?

Answer: Symptoms that your pet might have internal parasites include vomiting, diarrhea, weight loss, a decrease in appetite, dull hair coat, butt-scooting and lethargy. Some pets will have parasites in their vomit or stool that you will notice. You can also determine it by completing a fecal float test, which is what you’ll demonstrate today.

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Part 1: Preparing a Fecal Smear (25 minutes)

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Part 2: Fecal Floatation (20 minutes)

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Part 3: Analysis & Conclusion (10 minutes)

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Clean Up

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Popcorn Read

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Finding the presence of parasites is necessary for providing the correct treatment to an animal. Antibiotics and anthelmintic drugs are often specific to one type or class of internal parasite. If a producer treats an animal for the wrong parasite, the problem will persist. A veterinarian should identify parasites for treatment purposes, but he or she can use basic laboratory equipment to test for the presence of parasitic eggs. They can use fecal smears and fecal flotations to test fecal matter for parasitic eggs.

The fecal smear is a common veterinary technique that is one of the most used tools for the detection of internal parasites. By smearing a portion of fresh fecal matter onto a microscope slide and examining it, you can often detect minute amounts of blood, parasitic eggs, and other factors that can indicate an infection. A fecal smear can is an inexpensive screening exam at every checkup.

Another method for the detection of parasites in feces is fecal flotation, where the fecal matter is placed in a solution with a specific gravity greater than the eggs of the parasite, causing them to float to the surface. Fresh feces is preferable because many microbes and parasites will rapidly degrade when removed from the body. Veterinarians often recommend that fecal matter be less than 24 hours old to be used for a fecal smear. Will you be able to determine if parasites are present in fecal matter?

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Part 1: Preparing a Fecal Smear

Goal: Work in a team of three to prepare slides to evaluate for the presence of parasites. Prepare a fecal smear and a simple flotation. Compare the two tests and record which of the two are most accurate in detecting parasites.

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1. Examine the provided slide set and internal parasites poster to get an idea of the appearance of some of the most common internal parasites and their eggs.
2. Obtain a fresh fecal sample.
3. Perform a gross examination (with the naked eye) of the fecal sample and record your observations in your journals.
4. Obtain a clean microscope slide and coverslip.
5. Place a drop of water on the surface of the slide. Use a toothpick to add a small amount of the fecal sample to the drop of water and mix well.
6. Spread the mixed drop across the slide with the toothpick until it is thin enough that you can read these instructions through it.

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Part 1: Preparing a Fecal Smear

1. Using forceps remove any large particles or debris from the sample and discard them.
2. Gently apply a clean coverslip over the smear. The coverslip should sit flat and have no air bubbles.
3. Inspect the fecal smear at low power with a microscope. Scan the slide in the pattern shown in the image any features that stand out. Note: Many times, tiny air bubbles are mistaken for eggs. Air bubbles have a clear center and a much thicker black ring surrounding them.
4. If any of the objects appear to be eggs, increase the magnification, and observe at high power.
5. Sketch any parasite eggs you find in your journal.
6. Repeat Steps 4–11, replacing the water with a dilute iodine solution.

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Part 2: Fecal Floatation Test

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1. Collect 1g of a fecal sample in the medicine cup provided.
2. Add enough flotation solution to the medicine cup to cover the sample and mix thoroughly with a toothpick.
3. Prepare a test tube with a funnel and several layers of cheesecloth in a test tube rack. See image.
4. Pour the sample from the cup through the cheesecloth into the test tube.

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Part 2: Fecal Floatation Test

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1. Use a pipette to fill the test tube with a fresh flotation solution. Fill until a meniscus forms on the top of the test tube, as shown in the image.
2. Place a coverslip on top of the meniscus of the test tube. Do not allow the solution to drip down the outside of the test tube when the coverslip is applied.
3. Allow the setup to remain undisturbed for 15–30 minutes. Make sure the flotation solution is touching the coverslip to allow the eggs to float to the top and adhere themselves to the coverslip.

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Part 2: Fecal Floatation Test

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1. Remove the coverslip from the test tube by lifting straight up. You must lift straight up so eggs will not slide off the coverslip.
2. Place the coverslip egg-side down onto a clean microscope slide.
3. Inspect the slide at low power with a microscope. Scan the slide in the pattern shown in the image. If you observe any eggs, increase the magnification and inspect it at high power.
4. Sketch the parasite eggs you find in your journals. Identify as many parasite eggs as possible.

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Assessment/Conclusion Questions

1. How did your observations of the fecal smear compare to the flotation slide?
2. Which method do you think is more accurate? Why?
3. Why is it important to analyze fecal samples?

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Differentiation

One way to differentiate in this lesson is if you are short on time, you can have half of the class complete the fecal smear test and the other half can do the fecal float test. This will help with time restraints and it will give you ample time to clean up, since I would recommend disinfecting and allowing time to wash hands.

Remediation

Extension/Enrichment

An extension or enrichment activity could be to arrange a field trip to a veterinary clinic or a laboratory where fecal float tests are routinely performed. This hands-on experience will provide students with real-world insights and a chance to interact with professionals in the field. Additionally, invite a veterinarian, microbiologist, or a professional in the field of parasitology to speak to the students. They can share their experiences, discuss the importance of fecal float tests, and answer questions from the students.

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