Everything Horse magazine Magazine, October 2014 | Page 26

Diagnosis of
Equine Parasite Burdens
Would you take medicine if you were not ill?
Many of us would answer ‘no’ to the question above, and
yet we may be treating our horses with a wormer several
times per year without knowing whether the horse has a
worm burden.
Resistance of internal parasites of horses is increasing with
no new anthelmintics currently under development and
thus there is increased emphasis on a strategic approach
to parasite management. Parasite burdens vary amongst
members of a herd and research has shown that 20% of
the herd shed 80% of the parasite eggs and larvae seen on
pasture [1]. The key to effective management is identifying
the individuals with a high shedding rate and managing
them accordingly as well as managing the environment.
Free ranging animals such as zebra are constantly moving
to new grazing and so have a lower exposure to parasites,
unlike the average domesticated horse which may have less
than an acre of grazing for use all year round (see figure 1).

HOW DO I FIND OUT IF MY HORSE IS
AFFECTED?

The first step is to identify whether an individual is affected
– looking at general condition and demeanour is not an
accurate method. The most common method used to
assess parasite burdens in horses is by performing a faecal
egg count (FEC). This is not a worm count but measures the
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number of strongyle eggs within a sample of faeces under
the microscope using a specialised McMaster slide.

WHAT ARE THE ADVANTAGES?

The process is straightforward and cost effective to
complete (less than £10 per sample), with many saddlers
and veterinary practices offering the service, in addition
to a growing number of mobile technicians who will visit
premises and perform the test there and then. Whilst the
initial cost may include the FEC and worming the horse, as
Mary Lennon, head of Pro-FEC mobile services states, ‘Last
year (2013) I found that 75% of the horses I tested did NOT
need worming at the time of sampling’.

WHAT’S THE CATCH?

Horse owners should be aware that a FEC only reliably
shows up the number of Strongyle eggs which are shed.
It is not an accurate indicator of other species such as
tapeworm, bots and pinworm (sho