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SPRING 2016 ISSUE
EQUINE MATTERS
1 2
WORMING PRACT I CE
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Try to keep old and young horses
separate from the main herd as these
age groups tend to have higher egg
counts.
●
Give wormer doses based on an
accurate weight; use a weigh tape!
●
Quarantine newcomers for 48 hours and
treat with a moxidectin/praziquantel
combination wormer.
●
In the UK there is widespread resistance
of small strongyles to benzimidazole
wormers so their use should be
restricted to properties where efficacy
has been proven using a faecal egg
count reduction test.
●
Likewise, many properties have
ivermectin-resistant roundworm
(Parascaris
equorum)
and pinworm
(figure 4)
(Oxyuris equi)
populations - speak to
your XLEquine vet if you have wormed
your horse and seen no improvement in
clinical signs.
●
Look at the drug in the wormer, not
just the wormer name; there are many
differently named products but actually
only four classes of wormers:
benzimidazoles (fenbendazole),
avermectins (ivermectin and moxidectin),
pyrantel and praziquantel.
●
Drug classes should be alternated
annually to reduce risk of resistance e.g.
a.
Year one:
give ivermectin products for
FEC based deworming from late spring
to autumn; one of these treatments
could be combined with praziquantel
for anti-tapeworm therapy in the
autumn; give all horses a moxidectin
treatment in winter for encysted larvae.
b.
Year two:
replace ivermectin products
with pyrantel products for FEC based
deworming giving one in autumn at the
double dose for tapeworm control; give
all horses moxidectin encysted treatment
in winter.
●
Different drug classes have differing
lengths of persistence and therefore,
if an interval programme is used, the
interval between wormers should be
adjusted accordingly: moxidectin
13 weeks, ivermectin 8 weeks,
fenbendazole 4-6 weeks, pyrantel
6-8 weeks.
Best Practice: Horse Factors
FEC Key Facts:
Figure 2. Schematic diagram illustrating
that 20% of horses in any given field
provide 80% of the worms on the
pasture such that targeted treatment
of these high shedding horses is cost
efficient and helps decrease the risk
of resistance.
Figure 3. Encysted small strongyle
(cyathostomin, redworm) larvae in the
large intestinal gut lining
●
Base worming programmes on FEC
rather than using interval worming to
decrease the risk of resistance
developing to worming drugs
(Fig. 5)
.
●
Do not overstock pasture (provide one
grazing acre per horse as a rule of
thumb).
●
Remove faeces regularly from pasture
(at least twice weekly).
●
Co-graze pasture with sheep or cattle
to reduce pasture contamination.
●
Harrow on a hot, sunny day. This
exposes eggs to high temperatures
and reduces pasture contamination.
Harrowing in any other weather
increases contamination as it just
spreads eggs all over the pasture.
Figure 4. Irritation and trauma of the
skin around the anus due to pinworm
infection
Best Practice: Management Factors
Figure 5. Schematic diagram showing how the regular use (overuse) of worming
products in interval worming programmes leads to the development of resistance
to worming products.
●
FEC is a diagnostic test performed by
a lab to determine how many adult
egg-laying worms your horse has
●
Use of an FEC directed worming
programme reduces resistance of
worms to worming drugs AND saves
you money
(figure 2)
●
FECs only detect adult worms and
therefore a product (moxidectin) able
to kill immature worms (larvae) in the
gut lining
(figure 3)
should be used in
all grazing horses, once per year in
the winter, regardless of FEC results
●
FECs are unreliable for detecting
tapeworm infections as eggs are
shed intermittently and therefore a
tapewormer (praziquantel or double
dose pyrantel) should be given in the
autumn (+ spring if no poo picking/
many horses coming and going
on yard)