Running one
fecal sample test will let us know if your horse has worms, and how many
parasite eggs he's 'shedding' into the environment, but it takes a follow-up
test after deworming to get the whole picture. Here's why....
Doing
what's referred to as a 'fecal egg count reduction test' (FECRT) is like the
'before and after' of a home makeover on a TV show; using two tests in tandem
tells you what the interior of your horse's gut is like before consuming the
deworming medication, and what the horse's interior is like after the dewormer
has had a chance to work its magic.
But it
tells you even more than that. It also gives you insights into the dewormer's
effectiveness, and whether a trend toward drug-resistance has begun in the
parasite population on your farm.
___________________
Curious about whether your horse's parasites are resistant?
Using 'before and after' testing will tell you.
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To tell how
effective the dewormer was, look at the difference between the egg counts of
the first test and the follow-up test. This is called the FECR, or 'fecal egg
count reduction.'
A 90% FECR
is an acceptable minimum for benzimidazole and
pyrimidine dewormers, and a 95% FECR is good for ivermectin and moxidectin.
Anything less than that means either your horse didn't consume all the dewormer,
or you could have a parasite population that's 'resistant' or no longer
responding to that particular dewormer.
If
the percentage is lower than the acceptable minimums, you'll have to wait
before repeating the FECRT process. This time, make sure your horse eats all
the dewormer, and if you get a similar result, then consider your equine worm
population to be resistant to that dewormer. Since resistance is understood to
be a permanent genetic trait, once your horse's worms are surviving the dose of
that class of dewormer, it's 'hasta la vista, baby' to that particular drug.
Some
tips on FECR and FECRT:
-
Before you run the two-test FECRT process, make sure it's been
at least eight weeks since the last treatment with benzimidazole or pyrimidine,
12 weeks since using ivermectin, or 16 weeks since using moxidectin with the
horse(s) being tested.
-
Horses over age three can be tested for FECR; if you have a
large horse population, testing at least 10% of your herd can provide you with
adequate results. However, testing each horse at least once will tell you how
extensively they contaminate the environment through parasite egg shedding,
giving you a guideline into how frequently that horse needs to be dewormed.
-
Repeat
the FECRT annually, to identify changes that could point to developing parasite
resistance on your property.
