Tower Equine have put together an annual package that will make sure your horse is appropriately tested and wormed throughout an entire year.

Why Use the ‘Tower Equine Worming Programme’?

To explain how our worming programme works, we first need to look at why wormer resistance happens.

Wormer resistance

The key point to understanding why overuse of wormers is such a big problem is to appreciate that no wormer is going to kill every single worm. No matter which wormer you give your horse, a small number of the worms will survive - usually because they have a genetic mutation that gives them resistance to the wormer. Does this matter? If only a tiny number of worms survive, you might be tempted to think it doesn’t. But this small number of adults will go on to produce eggs which hatch into a new generation of worms, and some of these will have inherited the resistance of their parents. We have, unwittingly, selected for resistant worms. Each time we worm, we increase the number of resistant worms. In fact, the position is even worse than this, because we have wiped out all of the non-resistant worms, meaning that the resistant ones have a lot less competition. We haven’t just selected resistant worms, we have given them a helping hand! Remember, this happens every time we worm our horses, and this is why giving repeated heavy doses of wormers is adding to the problem.

Resistance to wormers is already widespread – some species of worm are currently no longer killed by two or even three of the different wormer types. Remember, we only have five different types of wormers, and new ones aren’t coming along any time soon! The problem is exactly the same as the NHS has with antibiotic resistance – people in hospitals are suffering infections and dying because the bacteria have become resistant to all the antibiotics available. We have to change what we are doing or soon we will no longer be able to properly protect our horses from worms.

How does this affect me?

Sometimes the temptation is to think that wormer resistance is somebody else’s problem. Surely it is up to the government or some other authority to sort out things out? If a good wormer is available, why not keep using that because at least then you can be sure your horse will be protected? You don’t want to take any risks, and as long as most people cut back, it won’t matter if you don’t…... This is a tempting line of thought, but unfortunately it is WRONG. If you overuse wormers, you aren’t increasing the general level of resistance in the UK, you are directly selecting for resistance on your very own fields! Resistance is local – you create it on your own paddocks.

The solution – Worm Egg Counting.

After all the bad news of wormer resistance, it is time for some good news. As they grow up, horses develop their own immunity to many of the most common types of worm. As the horse become resistant, adult worms are no longer able to live inside them, and worming is often no longer necessary. Fit, healthy adult horses generally carry only low levels of worms, and don’t need repeated worming. Of course this immunity only develops because the horse has had some exposure to worms when it was growing up –a completely worm free environment is not only rare, but also undesirable. The way to prove a horse has good immunity is to perform a Worm Egg Count (WEC). This simply means counting the worm eggs in a sample of the droppings using a microscope. From the number of eggs seen, we can get an idea of how many adult worms a horse is carrying in its intestines. If the WEC is low then worming is not necessary.

So far so simple, but there are a couple of things to be aware of. With one particular type of worm known as small strongyles or cyathostomins, the damage to a horse’s gut is done by the larvae, not by the adult worms. Because the larvae are not yet producing eggs, this means we cannot identify horses with a high level of larvae on a WEC. The good news is that cyathostomins are mainly a problem for young horses – adults are rarely affected – which is why the worming advice for youngsters is different to that for horses five years old or more.

The second small complication comes with tapeworms. Again, tapeworm eggs are not detectable on worm egg counts. Once again however, there is still an effective solution. There is not the same selection for wormer resistance with tapeworms as for some other worm types. Owners can therefore simply choose to treat horses with a wormer effective against tapeworms (once a year is fine for adults, twice a year for youngsters). Alternatively, an active tapeworm infection can be picked up with a kit that tests antibodies in the horse’s saliva. Both control methods work, so the choice is mainly down to cost and owner preference.

Wormer Types

Undoubtedly, some of the confusion around wormers arises from all the different brand names. Trying to remember your Animec from your Equest, or your Noropraz from your Molemec is enough to make anyone’s head spin. The best way to simplify things is to classify wormers by their active ingredient. There are only five different active agents, and all brand name wormers contain one or more of these. The five active ingredients are:

1) Ivermectin - Examples of ivermectin based wormers include Eqvalan and Noromectin. There is roundworm and some small redworm resistance to ivermectin.

2) Moxidectin - Equest is the only commercially available moxidectin wormer and has been considered as the ‘go-to’ wormer for effectiveness, but resistance is now being reported, particularly with regard to roundworms.

3) Praziquantel - This is effective against tapeworms. Now only available in combination, usually with ivermectin or moxidectin.

4) Fenbendazole - Panacur is the best known example of this. Main current use is in foals to control roundworms. Significant small redworm resistance.

5) Pryantel - Strongid P is the best known of the pyrantel wormers. Effective against tapeworms at a double dose.