How do Faecal Egg Counts work?
In the previous article on (de)wormers ("About wormers - A natural solution?") I mentioned FEC's (faecal egg counts). Some may already know what it is, without knowing how it is done, and others may have read this word thinking I was crazy person inventing weird concepts.
But FEC is exactly what it says: its aim is to count the number of worm eggs present in the faeces (in poo, that is).
The first FEC that I ever did was during my 2nd year in Equine Science when we were talking about the effect of worm in health and performance of our equine friends. I didn't really listen at the time - believe me when you don't really care (ie. you don't have your horse and you have never worried about these little buggers) it's not really fascinating to count worm eggs in poo, it's even totally annoying, to stay polite.
But then I started being more interested when I found out my horse had gastric problems. That's when I started wondering about wormers, and that's how what was discussed in the last article came about.
Thankfully (or not), I had the occasion to try again that wonderful experience when I did my work experience in a veterinary clinic from May to August 2016. I was then in charge of the laboratory work in the clinic, which included blood analysis, sterilisation of the equipment, etc. and of course, FEC's. The advantage is that I got to do my own FEC's for my own horse every month and for free, the disadvantage is that I was doing everybody else's horses as well... Even when it was for an entire stud farm with their 10 mares and their 10 foals.
Therefore, I am now more than familiar with FEC's, and how you do it! There are of course many ways to do it, but that's how I did it (simple and efficient!):
1. Start with 42ml of salt water solution (water saturated with salt)
2. Add a bit of the sample in order to arrive at 45ml
3. Mix the solution well so the sample is diluted into the salt water solution
4. Filter the solution in order to separate the particles of undigested material and the liquid - the eggs will have been attracted by the salt in the water and will not be retained into the filter
5. Fill up the slide (which is a special one with little squares to be able to count) without bubbles
6. Put the slide under the microscope and observe - look for eggs and count them
7. Multiply the result by 100 (so eg. if you count 5 eggs, you count will be 500 epg)
You can also recognise the type of egg that are in the sample - the most common being strongyle eggs.
Reminder:
epg<200: low count, acceptable, do not worm (or worm with a natural wormer if you aren't really sure how the other horses in the field are wormed)
200<opg<600: moderate count, worm with a natural wormer to avoid aggressive products and only to regulate the count
opg>600: infestation, use a chemical wormer to eliminate as many worms as possible including the migrating larvae in the organism
Note on tapeworms: FEC are unreliable to diagnose the presence of tapeworms which are unfortunately one of the common worms of the horse. Indeed, they don't lay their eggs on a regular basis, therefore you may have a horse infestes with tapeworms with a negative egg count, just because the worms didn't excrete eggs on the day you took your sample. Blood analysis will say if there is a tapeworm infestation.
