Worming and Resistance in Horses

Everyone knows how important it is to worm ourThe reason we do this is to ensure the worms within
horses regularly to make sure they are healthy andour horses are not building up a resistance to the
happy! This is especially important for those horsestype of drug in the wormers we are using - this can
that are on pasture 24 hours a day, but is alsobe a real problem as horses can carry heavy
important for stabled horses.infestations of worms in their gut even though they
A few tips for worming horses:are wormed on a regular basis, and start to lose
- Treat all horses grazing together at the same timecondition and become unhealthy.
and with the same product.Ensure that your horse gets the correct dose for his
- Take into account the horse's age and type, localweight. Don't under-dose as this can lead to
environment and climate.resistance in the worm population and the horse not
- Keep an accurate record of when you worm yourbeing wormed effectively. This is particularly
horse and the product used.important to remember when you have a larger
- Treat horses that are at grass during the winter,horse such as a friesian, as these horses often
even if only for short periods.Do not overstock theweight more than the highest dose level on the
paddocks.worming paste - often these pastes only go up to
- When moving horses to new grazing worm them550kg-500kg, and many friesians are over 650kg,
48 hours before the move to help prevent thewith our heaviest horse weighing in at around
spread of parasites.750-800kg!! The 'mectin' family of worming product is
- No single worming drug will kill all the horse's internalthe most common class of wormer used in Australia
parasitescurrently - wormers such as Equimax (abamectin),
- Do not administer the drugs more frequently thanEquest (moxidectin) and Equimec (ivermectin) are
recommended.some examples. The 'mectins' are very good
The key to worm control is to break the life cycle ofwormers, but there are growing concerns that
the parasite, through drugs and pasture management.over-use will lead to resistance in the horse industry
Killing the four main groups (Large Redworms, Smalland cause a loss of it's effectiveness.
Redworms, Tapeworms and Bots), will also kill all theHow to Avoid Resistance
other important worms. When you are moving fromGive the correct dose - especially do not under-dose
the warmer months and into autumn and winter, youUse an effective worming product (not a product
may notice Bot flies hanging around your horsewhere resistance has developed, as it may make the
(mainly their legs). These annoying flies lay small whiteproblem worse)
eggs on your horse in autumn, so using an effectivePrevent the horse from spitting the paste back out
boticide (ivermectin) when you worm at this time ofand reducing the dose he gets - put the wormer all
year.the way to the back of the tongue, and make sure
Worm Resistanceto hold the horses head up for around 15 seconds
If the active ingredient in a worming product is usedafter administering or until you can see that he
continuously on a property for a long time, there isswallows all of the paste. Rotate wormers (the drug
an increased likelihood that the worms (especiallynot just the brand) - this can be done yearly.
Small Strongyles) may develop resistance to thatMaintain good pasture hygiene - rotate paddocks and
family of drug, rendering the products no longerharrow in the summer months, or pick up manure in
effective. Make sure to rotate wormers every yearpaddocks, or clean stables out daily. These measures
or so - this means getting a different wormer with aavoid increasing the worm burden in the paddock
different active ingredient and not just a differentstable and hence also in the horse.
brand - make sure you read the label or askRemembering these simple steps and guidelines will
someone (such as your vet or the supplier of theensure that your horse is happy, fit and healthy, on
worming paste) which active ingredients are differentthe inside and outside.
from the wormer you have been using.