If you are interested in reading other parts of this series:
Barber Pole Worm Series Part 1-The #1 Killer Of Small Ruminants
Barber Pole Worm Series Part 2-Controlling Worms Without Dewormer
Barber Pole Worm Series Part 3-How To Properly Deworm
Barber Pole Worm Series Part 4-Breeding Parasite Resistant Sheep
Throughout our series on barber pole worms, we have mentioned several times that fecal egg counts (FEC) can be a very useful tool in a parasite management program. This is particularly true when breeding for parasite resistance.
Many people think that it is too expensive to use fecal egg counts regularly because you have to send samples to a lab or to your vet for analysis. Typically, this costs $10-25 per sample, which can add up pretty quickly. Fortunately, with a basic microscope and a fecal egg count slide kit, almost anyone can learn to do FEC at home. If you do more than a few FEC in a year, the investment in supplies to do FEC at home will quickly pay for themselves.
Doing FEC at home has the added bonus of giving you immediate results. Fecal egg counts are often used as diagnostic tools on a sick animal. You might have to wait for a couple days to hear from the the vet that your sheep has coccidia or parasites. If you do the test yourself, you will know 10 minutes later what is in your animal’s feces.
You need a few basic supplies
- Microscope that has 100x (10x lens) magnification. Worm eggs are large, so inexpensive student microscopes work perfectly.
- Paracount-EPG™ kit with the green grid lines on the slides.
- A container for smashing manure pellets in
- Craft sticks (or some other kind of small spoon you can crush and scoop manure pellets with)
- Disposable gloves
- Flotation solution. You can purchase a ready made flotation solution or can make a simple one yourself.
How to make your own flotation solution
We use a sugar solution. It consists of 1 lb of sugar dissolved in 12 oz of water. You will need to heat up the water for the sugar to fully dissolve. Once the sugar is dissolved, allow it to cool and refrigerate.
Alternatively, you can make an Epsom salt solution. To do this, put some Epsom salt in a jar. Fill the jar about 2/3 full of water. Shake or stir it until the salt dissolves. Add more salt, and repeat. Continue doing this periodically over 24 hours until you have a saturated solution evidenced by a layer of salt in the bottom that will not dissolve. You can then pour off (and save) the liquid leaving behind the undissolved salt. The liquid is your flotation solution. The remaining salt can be reused to make more flotation solution or disposed of.
Before we get started it is important to note
There are various ways to perform fecal analysis on animals. For animals like sheep and goats that tend to have high worm counts, the modified McMaster egg counting technique is preferred. You can use other methods if you choose, but this one is ideal.
Regardless of what method you chose to use, it is important to be consistent. Use the same technique, and the same flotation solution every time. You cannot compare results from your vet or a lab against your results, or the results of 2 different counting methods to each other. This is particularly true if a simple fecal flotation is performed. This method will tell you what species of eggs are present but will provide no useful information about how many worms are present.
Different FEC methods count eggs differently so results are relative and only comparable to other results obtained from the same test method. For example, the same fecal sample may show 1000 epg counted one way and only 500 epg counted using a different method. It is not so much the exact number that matters as being able to compare that number to previous or future FEC tests.
How to perform modified McMaster egg count.
Before we actually start working through the procedures, it is a good idea to take a few minutes to familiarize yourself with what some common parasite eggs look like. There are plenty of picture references for small ruminant parasites on the internet.
Then, you need to go gather poop! Many worm eggs hatch very quickly, so you will need to obtain a fresh sample. To do this, put on one of the disposable gloves. Stick one or 2 fingers into their rectum and carefully pull out some manure into your hand. Invert the glove off of your hand so that you have your manure in a glove bag. If you are doing multiple samples it is a good idea to write the sheep’s name/number on the glove.
You will need to either use or refrigerate your samples in under 30 minutes from collection. If you use old manure, or allow your samples to sit out at room temperature, most likely the worm eggs will have already hatched into larvae. Once they become larvae you can no longer see them on your test and you will get inaccurate results.
Once you have your samples collected, it is a good idea to put all but 1 sample in the refrigerator.
Next we will need to set up your microscope and prepare the manure for analysis
Set up your microscope, and make sure it is set to magnify 100x and get your Paracount-EPG™ kit out.
Dump the manure out into your large container and smash up all the pellets into little pieces. The better you do this, the easier the next steps will be.
Then take one of the large vials in your kit and fill it with flotation solution up to the ‘flotation solution’ line. Look closely at your vial before starting. It has a different line for horses than it does for sheep and goats.
Add crushed manure until you reach the fill line. Stir it vigorously until all of the manure is dissolved into a uniform brown liquid.
After you finish stirring, immediately use one of the syringes included in the kit suck up your solution. Carefully inject it into one of the chambers in the slide. Empty the syringe back into the vial and suck up a new syringe full for the other chamber of the slide. Remember to draw 2 samples from your vial. One for each chamber.
If you wish to redo your egg count on a given sample, be sure to give the manure solution a good stir before using it again. It is a flotation solution, so the eggs will all work their way to the surface, and you will not get accurate results without re-stirring the solution.
On to the microscope!
Here you are simply going to put your slide on the microscope and count the number of eggs within the grids. To do this focus your microscope on one of the green grid lines until the line is clear. Then find a corner of one of your grids. Carefully work your way up and down the grid tallying all of the eggs. Do not count eggs outside of the grids. Keep track of each different kind of egg separately.
Once you have finished with the first grid, repeat the process for the second one.
Take your time and be patient with yourself. Keep scrolling through your slide. Most likely you will eventually see a barber pole worm egg. Once you have seen a few of them, and you know what you are looking for they will become very easy to spot.
At first you might find some artifacts confusing
It may take a little practice to pick out your worm eggs from all the other artifacts. Things you might find under your microscope include not only parasite eggs, but also many other strange looking thing.
You will see lots of air bubbles. These are probably one of the first things you will see that you might think are parasite eggs. They are not. Air bubbles look like large black doughnuts. They are everywhere, and are super obvious once you know what they are. Ignore them.
You will see all sorts of odd looking shapes and debris. Most of them are part of plants cells and cell walls. You can tell this sort of thing apart from your worm eggs, because worm eggs are very consistent in size and shape, this stuff usually isn’t.
You might see pollen. It is a little trickier than most plant debris. It is extremely uniform and looks a lot like it might be some kind of egg, but it isn’t. If you aren’t certain, you can always do an internet search for pollen under the microscope to see what various pollen grains might look like.
Lastly, in addition to the various worm eggs, you may see coccidia.
It is a normal inhabitant of your sheep’s gut. If the animal is healthy and does not seem ill, it is not of concern. However, it is also capable of being a pathogen, particularly in lambs, where it can cause anemia like the barberpole worm. If you are looking at manure from an anemic sheep with a lot of diarrhea, and see a lot of coccidia, you will likely need to treat your lamb with a coccidiostat rather than (or in addition to) a dewormer.
Calculating your eggs per gram
Now you will need to do some math to determine the number of eggs per gram (EPG). This is the FEC count information you are seeking.
First add the number of eggs for each grid together to get a total. Do this for each kind of egg separately. If you used sheep/goat line on your vial, then you will need to multiply the number of worm eggs you counted by 50. If you used the horse line on the vial you will need to use a multiplier of 25. So, if you counted 1 barber pole worm egg, your EPG is 50 (1 x 50 = 50), if you counted 27 barberpole worm eggs it is 1350 EPG (27 x 50 = 1350).
The last step is to carefully wash and dry your tools. It is best to do this promptly before your manure solution has a chance to dry onto anything. Be gentle when washing the slides and vial. The grid lines and writing are ink and can be scrubbed off. Usually a thorough rinse under running water is sufficient to clean the slide chambers. You can then shake out the water and pat them dry on a clean cloth or paper towel.
What to do with this information
Fecal egg counts provide you valuable information about what parasites are present and in what numbers. Most of the time barber pole worms are the main worm of concern. Lower levels of most other worms typically do not reach dangerous thresholds before barberpole worms do.
There is no magic FEC number that tells you whether you should or shouldn’t deworm your animal. You have to use tools like FAMACHA and body condition scoring for that. However, a FEC can confirm your diagnosis. It can tell you that yes, that anemic animal is dying of barber pole worms, or yes that sheep that you can’t put weight on is loaded with brown stomach worms. It is also a valuable tool that you can use to select for parasite resistance, to track parasite trends in your flock, or even to test the effectiveness of your dewormer.
Doing your own fecal egg count reduction tests
Doing your own dewormer effectiveness checks can be quite useful in the current era of dewormer resistance. This dewormer effectiveness check is called a fecal egg count reduction test. To do a fecal egg count reduction test, take a FEC on your animals. Then deworm them. Repeat your FEC again 10-14 days after deworming them.
FEC reduction tests are expressed in percents. Divide your pre-deworming FEC by your post-deworming FEC, subtract it from 1 and multiply by 100 to get this percentage. For example, if I had a sheep with a pre-deworming FEC of 6540 EPG, and 400 EPG post deworming, what is my FEC reduction? Divide: 400 / 6540 = 0.0611 Subtract: 1 – 0.061 = 0.09389 Multiply: 0.09389 x 100 = 93.89% reduction. Not great, but could be worse.
In a perfect world the 10-14 day egg count would be 0 or a 100% reduction. If you get less than an 80% reduction then you very likely are dealing with some significant parasite resistance problems. Once you get down towards 50% you are looking at a complete failure of your dewormer.
We hope with this information has provided you with a new valuable tool. You are now ready to get started doing your own fecal egg counts!
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