| Winter’s
dormant months mean that many horses won’t have
access to grazing - the main route to a parasite burden.
However this doesn’t mean your worm control
programme should also be dormant. The experts at Pfizer
Animal Health discuss what you should consider for
winter worm control, to give your horse the best preparation
for the spring and summer ahead.If you are following
a responsible worm control programme you will have
strategically dosed for tapeworm, encysted small redworm
and bots by now. If you haven’t yet treated
your horse for these parasites a practical and cost-effective
solution is to give a single dose of moxidectin and
praziquantel.....but what next?Hopefully you use faecal
worm egg counts (FWECs) during the spring and summer
as the basis for your roundworm control programme
along with good management of your pasture. Control
over winter requires a slightly different approach,
not only because many horses spend much less time
at grass and so won’t pick up worms through
grazing but also because worms don’t cycle in
such great numbers when the temperature drops. This
means that Faecal Worm Egg Counts are not as useful
during the winter because many redworm may not be
completing their lifecycle so fewer eggs may be seen.
In theory low exposure to worms means that there
is less need to give a routine dose unless you are
particularly concerned about the level of worm burden
on the pasture being grazed. For horses on winter
turn out it is best to assess the overall risk from
the pasture and worm accordingly but stabled horses
treated appropriately in late autumn should require
minimal treatment at least until turnout. The only
complicating factors are tapeworm and in some cases
pinworm as neither are exclusively transmitted during
grazing and are not reliably detected in FWECs. Tapeworm
should still be controlled twice yearly in most cases,
although the overall risk can be assessed by a tapeworm
antibody test conducted by your vet. Pinworm, however,
won’t show up reliably in any tests. They lay
their eggs around the anus causing itching and are
rubbed off by the horse. They can be transmitted from
horse to horse via things like stables, buckets, hay,
bedding and grooming brushes. Prevention includes
good stable management, but treatment will be necessary
in the case of an established burden.Spring turnout
is the most important time to think about your next
steps for worming. The key question is how much exposure
has your horse has had over winter? If you dosed correctly
in early winter, minimal exposure from then on means
that treatment prior to turnout may be unnecessary.
However, your strategy may also depend on the grazing
you intend to use. Clean pasture, that hasn’t
been grazed for at least six months or has experienced
hard winter frosts, will hopefully pose a lower risk.
In this case it may be sensible to turn out and then
use an FWEC to monitor how the worm burden is developing
over the grazing season.
However, turning a horse onto pasture that has been
used heavily (worm eggs can survive on pasture from
the previous year) means you will need to be very
conscientious about your worm control programme during
the grazing season. It’s useful to bear in mind
that the persistent effect of some wormers, such as
those containing moxidectin, means that once your
horse has been treated it will continue to ‘clean
up’ the pasture for a couple of weeks afterwards.
Dosing at turnout, or ideally a few weeks after turnout
may reduce overall pasture worm burden, which could
in turn reduce the number of worming doses your horses
need over the summer months.
Ben Gaskell, Pfizer’s veterinary adviser concludes:
“Even though your horse may be less exposed
to worm infection over the winter it pays to stay
on the ball with your worm control programme. Better
management at this time of year means that you will
be better placed come turnout time and subsequently
may need to worm less during the summer months.”
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