It is no secret that horses are showing resistance to modern wormers, specifically the Benzimidazole group of drugs. As a consequence, there has been increased uptake on the ivermectin based products and also Moxidectin.

There are currently no plans to introduce new anthelmintic products i.e. wormers and so what is available on the market now, needs to be used as sparingly as possible and combined with other management protocols to prolong the availability of existing wormers.

There are a number of steps you can take to manage your horse’s worm burden, part of the collective responsibility of all horse owners to protect their animals and avoid the situation where there are no wormers left on the saddlery shelves – a real possibility.Read our guide to learn more about you can help control your horse’s worm burden without just reaching for a syringe.

Collect droppings from your horse’s pasture if not daily then every two or three days

• Mix species so graze with sheep or cattle where possible
• Keep muck heaps away from grazing pastures
• Be as accurate as possible when dosing your horse. Dosages are based on weight and under dosing is one of the key reasons for the development of resistance; you use the medicine but not at a level which is effective, thereby not only failing to treat the worms but also encouraging an environment where they are sufficiently exposed to the drugs to begin to develop resistance. This is called the sub therapeutic level
• Ensure your horse actually receives the full dose. Some horses are difficult to syringe but lumps of wormer falling onto the stable floor mean that you have actually underdosed your horse
• Use worm counts to monitor your horse’s parasite burden. If you keep your horses at home without any transient population then worm counts may be sufficient to keep your horses healthy and happy, remembering of course that encysted redworm will still need treatment in the winter months and also tapeworm possibly spring and autumn.

Take the example of one owner who has kept between two and three horses on the same land for 13 years and used a faecal worm count every three months. She has the occasional visiting horse to use the arena but they do not graze her paddocks. To date, she has never had a reading of more than 50 epg – eggs per gram – other than on one occasion with an old horse with lowered immunity and other health issues who did then require worming. She has not, therefore, followed a conventional 6-week worming programme at all, worming only for tapeworm and encysted red worm in the winter and used no other wormers for the entire 13 years.

Do not use tapeworm treatments but consider instead the new saliva test

• Isolate new arrivals on the yard from other horse’s pasture until they have either been wormed or had the results of a faecal egg count
• If you do need to worm a horse, be clear what you are seeking to target and which is the best product to do this. Your vet or a testing laboratory can advise on one-off worming situations or write a programme for your new horse
• As well as accurate dosage and appropriate choice of drug, the timing of administration is key. These three things form the holy trinity of successful worming, get any one of them wrong and you are wasting your time and money and potentially starting a process in that horse where he will become resistant
• If you have always followed a set worming regime, be open minded and review it with your vet or other suitably qualified person

Worms are a clever parasite that can evolve and change to counteract and circumvent drugs which horse owners have relied on for decades. Horse owners are now going to have to match this ability to change by altering their tried and trusted methods of worming, embracing new ideas and taking a more proactive role in managing both horses and the pasture they graze on.

Gone are the days of squirting a tube of medication and forgetting about the problem for a few weeks.The message has been in the public domain for a long time now, at least a decade, but not everyone is taking it seriously or can understand the implications for the horse. Those who are old enough to remember will cast their minds back to parasite-related health issues, principally colic caused by massive worm infestations. No-one wants to go back to the bad old days.

So the takeaway is, protect your key medicines and do everything you can in your horse’s environment to reduce the worm challenge your horse encounters.