1 – The life and crimes of equine parasites

Doing your own faecal eggs counts should be a key part of your worming strategy.
Doing your own faecal eggs counts should be a key part of your worming strategy. © Horsetalk.co.nz

How the worm turns

Life would seem to be pretty rosy as an equine parasite. Living inside a horse offers a warm and comparatively stable environment, with the necessary nutrients immediately to hand.

Parasites in horses have been around a long time. Their prevalence has ebbed and flowed with the fortunes of the horse over millions of years.

During that time they have developed specialised niches and have caused horses varying degrees of grief.

Some are comparatively harmless but others can cause complications and disease severe enough to kill the host horse.

In short, you ignore equine parasites at your peril.

Mankind has developed drenches, more properly called anthelmintics, to tackle the worm burden of horses.

They have proved effective but the raft of parasites that affect horses haven’t survived millions of years without learning a trick or two.

Drench resistance is becoming a growing problem and concern.

Some drenches have become relatively ineffective against resistant varieties. This is bad news for horse owners, as this is a battle they cannot afford to lose.

This series will explore the whole issue of equine parasites. It will do so in simple terms and will provide practical guidance for horse owners.

Unfortunately, in this war, there are no simple answers. There is no “one size fits all” solution. Each horse owner must assess their own situation and apply the knowledge to their own worm-control programme to best effect.

Parasites are not without their problems.

For one, they need to find their way from one host to another to ensure the long-term survival of the species. To do this, most have developed life cycles that see them exiting one host in the hope of infecting another.

The horse owner’s aim is to break this life cycle and keep parasite numbers within their horses within acceptable limits.

This series will look at the life cycles of each of the common parasites and the strategies they use for survival. This is important as horse owners can use this knowledge to their advantage, exploiting the weakness in the parasites’ “game”.

It will explore the variety of drenches available and their known strengths and weaknesses. It will look at management practices that will help your deworming programme and will explain how to conduct your own fecal egg counts.

While fecal worm counts have their limitations, it will give horse owners a valuable opportunity to tailor worm management programmes to each of their horses.

This is a sound option as research has shown that some horses harbour very few parasites while others quite quickly develop heavy worm burdens. The majority, of course, occupy the middle ground.

If horse owners know the susceptibility of each of their horses to parasites, they can develop strategies and dosing regimes that reflect this.

Regular fecal egg counts also mean you avoid dosing horses when their worm burden is low. For horses that quickly develop heavy burdens, you may end up dosing more regularly.

Effective worming strategies mean you are playing your part in minimising the advance of drench resistance.

It is important to bear in mind that effective parasite control is not a straightforward business, even though it is nice to think that regular drenching with any one of the brands available off the shelf will do the trick.

Your ultimate goal should be to maintain parasite levels at low levels in your horses. You want to achieve this using sensible farm management practices and using drenches only when necessary and to maximum effect.

This two-pronged strategy will ensure you’re playing your part in reducing the growth of resistance in parasites.


» Next: The numbers game




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