Help with McMaster FEC Test

[MapleFarm]

Hello!
I am wondering if someone here can help me with doing my own FEC test. I have a microscope and purchased the Eggzamin McMaster Method slides (https://www.eggzamin.com/eggzamin-products/eggzamin-fec-accessory-kit) but my results seem much higher than I would think.

I have two mares who are very healthy and shiny, are out pretty much 24/7 on a lot of land (15 acres-ish). I dewormed in April with Quest, and then this fall have tried an herbal dewormer as they have historically been low-moderate shedders. I thought I’d test to see if it was working. In November, I sent off manure for FECs and got the results of 18 EPG for Mare 1 and 74 EPG for Mare 2. After doing the herbal dewormer I wanted to see if these dropped or if I should hit them with a fall dewormer now that we’ve had solid frosts (I’m in VA).

I did the test yesterday, and I believe I followed all instructions correctly. I measured the manure - 4 grams on a kitchen scale (yes, my husband hates me) - with 26 ml of the solution. Filled both chambers and counted 40 eggs for Mare 1 and 83 for Mare 2. This is a count of all eggs within the grid pattern on each side of the slide (combined). The instructions say to multiply that by 25. This would give me 1000-2000 EPG. I feel like I am definitely doing something wrong but I’m not sure what!

[Texarkana]

It sounds like you did everything right. What you pictured is indeed a strongyle egg, and if that’s only what you counted, your technique is correct. Unless something in your measurement of the manure was incorrect.

1000-2000 EPG is a pretty typical high burden, not abnormally high by any means. Granted, you normally don’t see such a high jump in a matter of weeks… but it’s not unusual for a horse to go from 0 or low to 1000 in a matter of months, especially with stress or life changes.

I also think sometimes when you send samples out you may get false low counts due to eggs hatching while the manure sits around. I’ve noticed my counts are lower if I let manure sit all day before counting, even if I keep it cold.

[hoopoe]

I have not worked with the particular product myself but counting chambers I have worked with can give inconsistent number results when over or underfilled. My work has been with cancer cells and blood cells.

[Texarkana]

@hoopoe

I have not worked with the particular product myself but counting chambers I have worked with can give inconsistent number results when over or underfilled. My work has been with cancer cells and blood cells.

True, but you really can’t overfill a McMaster Slide. It’s a sandwich plate chamber.

[MapleFarm]

Interesting!! I’m glad I’m testing myself then - thank you for the insight!

[jlm0305]

A few things.

Counts don’t go down very much over the course of a day or even two weeks if kept in the fridge. Strongyle egg hatching occurs very, very slowly at low temperatures.

In my experience - and I’ve got a lot of it as the bulk of the studies I’ve published revolve around FEC methods - if counts are drastically different it’s because the sample wasn’t properly homogenized. So, you followed the AAEP method, but before you filled the slide with your filtered poo slurry, did you give it a good swirl? Because leaving it sit for even 30 seconds allows eggs to start rising to the top and if you then take sample from the top and fill your chambers, the eggs are more concentrated than they should be.

Now, that being said, there’s a lot of places that just aren’t good at doing fecals. So it could’ve been techs that weren’t properly trained, or a different method was used (it can make a substantial difference), or or or.

It’s also important to remember that FECs are highly variable. I’ve run replicate counts on manure from the same horse with ranges of 200 - 1500 EPG. It is far from a perfect science, particularly due to inherent natural variability in egg distribution, shedding, species composition, etc. The really good way to do them (and how we do it for studies) is to run replicate counts and take an average.

Just to prove to yourself how imperfect this all is, go ahead and count multiple slides just from the same poo slurry and see how much variation there is

[JB]

Herbal dewormers don’t work No study has shown they do, and several have shown the stuff tested didn’t.

DIY FECs is a GREAT thing to do, it lets you easily and quickly test efficacy, and keep tabs on if horses are changing amount low/mid/high shedding status.

[MapleFarm]

Ahhhh, ok, I think I may have found a potential issue. I did give it a swirl - but the Eggzamin instructions did not say to filter - so I struggled with material getting into my pipette and definitely it sat still while I suctioned.

Thank you for the detailed info! I’m running a new one today and I’ll do a few to get an average.

[MapleFarm]

I mean, I’m truly a skeptic but I thought I’d try it and do my own test to see! Obviously my number isn’t lower than it was, but perhaps it isn’t as high as I thought. I’ll re-run using jlm’s feedback above today to see where they are.

My question now is should I still do a dewormer in the fall, if their counts are quite low (based on mid-november “official” test numbers above)? I’ve seen different recommendations from vets online about fall dewormer for low shedders, and I’m trying my best to not over-medicate!

[JB]

FECs will never show you bot issues because eggs are never in the horse. And if you happen to see a tapeworm egg, you can probably assume the load is large. So when you have those to consider - you have botflies, the horse eats grass - you need to target them in the Fall - Equimax or Quest Plus

Way, way WAY too many vets have taken the FEC-based deworming protocols to mean never deworm in the presence of low/clean FECs, which is just so incredibly disappointing

[jlm0305]

Mmm, that’s not really true regarding tapeworms. You can just assume that they have them because they probably do, but seeing an egg does happen with lower burdens. We barely ever see them even with horses we know have super high burdens, but then with that resistance study Martin published they were seeing tons of eggs! It’s a crapshoot with tapes unless you use special methods; luckily they’re pretty benign for the most part.

@MapleFarm, check out the instructions in the AAEP Parasite Control guidelines. Cleaner samples are easier to deal with all around. If you have any questions, go ahead and ask! I’ve done thousands and thousands of fecals; the joys of a parasitology PhD.

[MapleFarm]

Thank you so much, I definitely will!

[Demerara_Stables]

@MapleFarm I had no idea that it was so “easy” (ok not really easy, but doable with tools and education) to do you own FECs.

Can you share an estimate on what you spent for all of the tools and what resources you used to learn how to do it?

[Texarkana]

@jlm0305

Now, that being said, there’s a lot of places that just aren’t good at doing fecals. So it could’ve been techs that weren’t properly trained, or a different method was used (it can make a substantial difference), or or or.

More than 2 decades later, I still vividly remember being a young tech living in the world of “see one, do one, teach one.” Training was rushed, incomplete, or even non-existent. A lot of “the blind leading the blind” at times.

[jlm0305]

The number of techs who tell me they can count an entire slide or go through an entire fecal float slide, including looking for Giardia in 30 seconds or less is extremely alarming.

[MapleFarm]

Yes, sure!

I bought this microscope: AmScope - 40X-2500X LED Digital Binocular Compound Microscope with 3D Stage + 5MP USB Camera (Amazon isn’t linking from my phone for some reason): $273
https://www.eggzamin.com/eggzamin-products/eggzamin-fec-accessory-kit : $67

That included everything I needed to do it! So $340.

The microscope we wanted to use to look at some other things on the farm and I may get back into doing some Dendrochronology for fun at some point, which I studied in college/grad school.

I used the eggzamin instructions and watched some YouTube videos. The additional info here has been very(!) helpful though, I got a way lower count today when I was more careful about stirring the slurry.

[Texarkana]

@Demerara_Stables It’s really a very easy skill to learn.

For years I’ve wanted to start some sort of FEC education clinic service: charge people a few hundred dollars and provide all the necessary materials for the attendees to keep. Spend the day teaching everyone the basics so they can go home and monitor their own herd.

[George_T_Mule]

Hi MapleFarm

I kinda skimmed thru, so pardon it if this a repeat.
In conjunction with my last gainful employment, I spent considerable time with the things. I still keep two on my workbench.
Like anything, learning to work under a microscope takes practice. And practice. And . . .
One thing you can do is to make multiple slides from the same source, count 'em all, wait a bit and count them again. If you aren’t getting similar counts from slide to slide, your sample preparation is questionable. If you are, run an an average and call it good.
If you do something often enough, you will develop a higher level of confidence in your technique, so there is light at the end of the tunnel :-D.

[MapleFarm]

Good advice, thank you! I worked under a microscope for about 6 years… but doing very different things from this so I definitely need practice. I was able to replicate my results today through different preparations staying close to an average - new mixes etc. I think letting it sit was my biggest error, as trying this got me numbers 2-3x higher or more!
I have some other things I want to test out to see if it is easier / changes my averages (I did not filter/sieve the material and this is still very annoying). I didn’t want to appropriate a kitchen mesh sieve, I have to draw a line somewhere