Q.

Can you learn to do your own fecals?

A.

Yes. All you need is a microscope, special egg counting slide, some flotation solution, and a few other inexpensive supplies. And, of course, feces. Lots of feces!

Microscope
You do not need an expensive microscope for fecal egg counting. In fact, you don't want too fancy of a microscope. It will provide too much confusing detail. Microscopes that are capable of 100x magnification (10x objective x 10x eye piece) are usually sufficient. A student microscope. It is recommended that the microscope have a mechanical (movable) stage. This will make the task of counting eggs easier.

Microscopes can be purchased from Amazon or science supply companies. Refurbished ones are sometimes available. Sometimes, you can get microscopes from high schools and colleges that are updating their science labs. If you do a lot of fecal samples, a compound microscope (one with two eye pieces) may be preferred to a monocular one (one eye piece)

McMaster slide
You need a special slide to count eggs. It is called a McMaster slide. It has two or three chambers which you fill with solution. Two chamber slides are most commonly used, though a 3-chambered slide will have more sensitivity. There are several sources of McMaster slides. Slides cost $15-$20 each. Buy the ones with green lines. Green lines are easier to see than black lines.

You need to be careful cleaning McMaster slides. Use warm running water to clean them. Do not soak the slides in warm soapy water for long periods as this will cause the chambers to become cloudy. Soak dirty slides in warm soapy water for only a few minutes at a time. Do not use acetone to clean the slides. It will erase the lines.

Flotation solution
You need a flotation solution to make the parasite eggs float to the top of the slide. In water, the eggs will sink. Flotation solutions are denser than water. They have a higher specific gravity. There are many flotation solutions that will work. The most common are saturated salt or sugar solutions. You can make these at home. You can also buy commercial flotation solutions, e.g., Fecasol®, Feca-Med®.

You should have a scale to weigh feces. You can buy an inexpensive gram scale from Amazon. Get a scale that weighs in 0.1 g increments. A digital kitchen scale will work. Instead of using a scale to weigh feces, you can use a volume displacement method (using a syringe). Other supplies that you need include paper or plastic cups, a measuring cup (or large syringe), stirrers (tongue depressers, craft sticks, or popsicle sticks), something for straining (cheese cloth, tea strainer, or unfolded 4x4 gauze), and pipettes (or eye droppers or 1 ml syringes).

Step-by-step
The first step in fecal egg counting is to collect a fresh sample of feces (2-4 g). A good size adult fecal pellet is about 1 g. Make sure the sample hasn't been contaminated by soil or bedding. The best way to get a sample is to put on an exam glove, apply some lubricating jelly to your finger(s), and collect the sample from the rectum of the sheep/goat. You can also use a fecal loop to collect feces from the animal. Be gentle when collecting fecal samples, especially from young or small animals.

It's okay to pick fecal samples up off the ground, so long as they were recently deposited, and you know from which animal they came. Try to keep each animal's sample separate. Put them in ziplock bags and label them. Samples can also be stored in inverted exam gloves. If you're going to collect very many samples, it's best to put the samples in a cooler (on ice) until you are able to analyze or refrigerate them. It's better to examine fresh samples, but the samples can be refrigerated for later analysis. If the samples are not refrigerated, the eggs will hatch in 12 to 24 hours. Do not freeze the samples.

Weigh 2 to 4 g of feces and put them in a paper or plastic cup. Smash them with the tongue depresser. For a 4 g sample, add 26 ml of flotation solution to the fecal matter. For a 2 g sample, add 28 ml. Mix the feces with the solution and let it soak. After approximately 5 minutes, strain the solution into a second cup, pressing the fluid through with the tongue depresser. Immediately fill both chambers of the slide with the solution. Fill the entire chamber, not just the area under the grid. If large bubbles are present, empty the slide and refill it.

Set the slide aside for 5 minutes to allow the eggs to float to the surface. Read slides within an hour. Place the slide on the microscope stage. Bring the grid lines into focus. Count all eggs inside both chambers of the grid using the 10x objective. Use the mechanical stage to move up and down the grid. For a 4 g sample, multiply the number of eggs by 25 to get eggs per gram (EPG). For a 2 g sample, multiply by 50. The multiplication factors are specific to the ratio of feces to flotation solution. The egg count will be for strongylid eggs (oval shaped). If you want to know the species of strongyles, you'll need to send a fecal sample to a lab for larvae culture, as the common worm species cannot be differentiated at the egg stage. Other parasites present (e.g., coccidia) can be counted, but numbers are more difficult to interpret.

This is one method of fecal egg counting (modified McMaster). Different labs may have slight variations in the procedure. What's important is that you use the same method each time. The more samples you do the easier it will become.

If fecal egg counting sounds like too much work (it's not for everybody), you can submit samples to a veterinarian, state diagnostic lab, or private lab. The cost will probably be too expensive for more than a few samples. Fortunately, several land grant universities are now offering low cost fecal egg counting ($5/sample) for the purpose of fecal egg count reduction testing and genetic selection (NSIP). The cost does not include interpretation or recommendations. You need to talk to your vet or figure it out yourself. Sometimes, universities have grant projects that can pay for fecal egg counting for participating farms.

Use the results of fecal egg counting to determine treatment efficacy, test for dewormer resistance, identify resistant animals, and monitor pasture contamination. Don't use fecal egg counts for making deworming decisions unless you have other information, e.g., FAMACHA© score, body condition score, ADG, etc.


05/10/2021


Additional reading
How to do the modified McMaster fecal egg counting procedure
Guide to internal parasites of ruminants - Intervet