Parasites in horses: are you playing your part?

Strongyles are a common horse parasite that pose a major threat if burdens are not properly managed.
Strongyles are a common horse parasite that poses a major threat if burdens are not properly managed. © Martin Krarup Nielsen

Denmark’s approach to parasites in horses should have owners around the world thinking about how well they manage the worm burden in their animals.

Horse owners in Western countries largely take for granted the fact they can walk into any saddlery or veterinary clinic and buy a drench. There are unlikely to be questions about what parasites you intend targeting or whether the active ingredients in that particular brand will do the job you intend.

Denmark changed all that in 1999.

Over-the-counter sales went out the window and sales of drenches, more properly called anthelmintics, became prescription only. It placed worm control firmly back under the control of veterinarians, who have to be satisfied a horse’s worm burden is such that it requires dosing.

Many horse owners would see this as a bad idea and only adding to the cost of worm control in their animals.

However, Denmark may not be the last Western country to tighten controls over drenches, as concern grows worldwide over parasite resistance.

The unfortunate reality is that many horse owners use drenches inappropriately and, in doing so, are fuelling the growth of parasite resistance to drenches.

There are many brands of drenches available around the world, but there are relatively few active ingredients. In other words, there are only a handful of chemicals that are proven to be safe and effective in worm control.

With no new families of drenches waiting to be launched on the market, it is every horse owner’s responsibility to use drenches wisely and effectively while at the same time ensuring they are doing their bit to minimise the growth of worm resistance.

Horse owners also need to employ other measures around their property to minimise drench use.

For decades, horse owners have relied on regular dosing with drenches every six or eight weeks to keep worms under control. They do so without any particular evidence that the drench being used is effective, or even that the horse needs to be drenched at all.

Parasitologists are now largely of the view that horse owners need to be smarter in their drench use. They need to monitor whether the drench they are using is effective and determine whether the horse needs the dose in the first place. Both of these can be achieved through faecal egg counts.

Eliminating parasites from horses is not realistically achievable. Horse owners need to implement a worm control programme that makes responsible use of drenches, as well as sound pasture management, to keep their horse’s worm burdens at sufficiently low levels to avoid health problems and disease.

Horsetalk will be placing online over the next few weeks this new major series on worm control in horses. It will deal with the major parasites of horses and explain the use of drenches, as well as their strengths and weaknesses. It will provide an easy-to-follow guide to doing your own faecal egg counts and outline other strategies to minimise worm burdens.

The 25 or so stories in the series will be regularly updated to ensure we’re providing you with the latest and best advice on worm control.

Denmark’s move to tighter drench control some 10 years ago was an acknowledgement of just how serious growing parasite resistance has become, especially in relation to the most troublesome of parasites, the nematodes known as strongyles.

While the jury is still out over the success or otherwise of Denmark’s move, it is a clear and present reminder to horse owners that, as long as drenches can be bought over-the-counter, the responsibility to control the growth of worm resistance rests in their hands – and no one else’s.


» Next: The life and crimes of equine parasites

First published on on February 2, 2009

Latest research and information from the horse world.

Leave a Reply

Your email address will not be published.