Count Down To A Successful Equine Deworming Program
By Nikki Alvin-Smith

In the past few years the approach to equine deworming has significantly changed. Are you up-to-date on the facts and do you utilize the best protocol in your horse’s parasite control program or are you still operating with a circa 1970’s mindset?

As an experienced horse breeder for more than 25 years, an advanced level competitor and lifelong horsewoman, the management of the parasite population in my horse herd is extremely important. Back in the 1970’s and 1980’s when the efficient paste de-wormer Ivermectin was introduced to the market, it revolutionized the way horse owners across the globe administered worm control remedies to their equine partners.

When I arrived in the U.S.A. in 1981, it took my husband (who is also an advanced competitive rider) and I, just six months to purchase our first horses. At that time we had no property here of our own, so boarded the horses at Caumsett State Park on Long Island, NY.

On the first vet visit, the routine Spring vaccinations were implemented and the vet suggested he would give my 15 year old ex Grand Prix showjumper, McCloud, and his equine compatriot, Gemini, an injectable Ivermectin wormer. This came as some surprise to me. In England I had enjoyed donkey and pony ownership and ridden throughout my youth at professional show stables and our routine for deworming was for the vet to take an equine fecal sample and do a worm egg count and then advise us what to use if anything, for worming control. We utilized powdered wormers top-dressed in their feed if needed, following the results. We did not retest until the following year.

With assurance that the injectable wormers was the latest and best method for worm control, I heeded the vet’s advice and let him go ahead. Little did I realize this new method was in its 2-year ‘field-testing’ phase. Shortly thereafter my vet received a call from me, a very panicked horse owner. Within hours my horse had exhibited a large swelling on his side by his heart, and had labored breathing. My vet responded and treated the horse. I cannot recall with what, but the horse recovered and the swelling subsided much to my relief. It was a long night and I’m sure I was completely useless at work the next day.

Thereafter, it wasn’t long before the injectable wormer was removed from the market, and in its stead appeared the paste dewormers. These heralded an effective, easy to use method every horse owner could administer.

The problem today, is that due to the overuse of the Ivermectin, and other dewormers on the market that belong to three major categories, certain worms exhibit an increasing resistance to these wormers.

The three categories of wormers are:-

Macrocylic Lactones ~ Ivermectin and Moxidectin
Tetrahydro Pyramides ~ Pyrantel Tartrate and Pyrantel Pamloate
Benzimidazoles ~ Fenbendazole,  Mebendazole and Oxibendazole

Additionally, Praziquantel has been added to this list, as a treatment for tapeworm that has been combined mostly with the macrocylic lactone, Ivermectin products for administration.

To counter this resistance problem a new protocol was promoted suggesting that we worm our horses in a rotational program, switching between the three major deworming categories. Like most other horse owners I adopted this method too. Obviously, it is important to rotate by the active ingredients in the type of wormers and not just rotate through brand names.

However, even this method has not proven to be effective at culling resistance. Products such as daily feed through fly control anti-parasitic treatments, and the 6-8 weeks calendar for de-wormer administration has led to an increase in worm resistance to our arsenal of present day products and unfortunately, according to expert equine parasitologist, Dr. Martin Nielsen, DVM, PhD, Dipl. ACVM at Gluck Equine Research Center, University of Kentucky, sadly there isn’t much new on the horizon treatment wise.

I am sure you are well aware of the benefits of pasture management to control parasites on your fields. If you have larger pastures then grazing rotation, by which I mean leaving the pasture free of horses or other livestock for a year can be useful. I doubt many of us have that option due to the need to utilize all our fenced grazing space.

Vacuuming or picking up manure is the best protocol. Harrowing the pastures in the Fall used to be popular as the thought was worms can’t survive exposure to frost. Unfortunately this isn’t true. Certain worms simply hibernate in their host the horse or in their host the foraging mite, or are resistant to damage from cold weather.

If you are going to harrow the pasture it is actually suggested you mow it and harrow before a hot dry spell as worms can be killed with exposure to U.V. light and heat. The shortened grass exposues the manure to more light and the harrowing disturbs the piles and breaks up the manure balls to expose more larvae. Otherwise, you are simply spreading the worm larvae about the pasture and your foraging horse will not be able to detect where to eat and what grass to leave alone. As we all know from the pattern of manure distribution on the field, horses try to leave their manure in certain areas and graze elsewhere.

So how do you as a diligent horse owner, protect your horse population from the myriad of parasites that can damage stomach and intestinal mucosa, migrate to lymph, liver and lung tissue and cause disease and illness such as impact colics, foal deaths, unthrifty development and discomfort. It appears the science has come full circle and the fecal egg count test or F.E.C.T. is again the suggested method of choice for parasite management.

In fact, it makes perfect sense that we should do an F.E.C.T. on a regular basis for each of our horses that are in our care, when you consider that we have been worming our horses blindly, using a random administration of products without any testing at all and consequently no knowledge of whether the products are working or whether we are just wasting our time and money and not solving the parasite issues in our herd.

By the time a horse exhibits signs of disease of distress, it is a bit late in the day to resolve a worm issue, especially in young and elderly horses, whose underdeveloped or tired immune systems make them particularly susceptible to parasite damage. We need to know which horses are shedding worms and in what numbers, and specifically if the horses in our herd are shedding wormer resistant larvae on the pasture for the rest of the herd to ingest.

In training our horses we treat all of our horses as individuals, and follow a training regime that makes sense for each particular horse. The same should be  true in our worming protocol.

All horses shed worms and no worming program will completely eradicate all equine worm populations. Some horses will naturally harbor more worms than others and appear to be completely fine operating with a higher shed rate level. These horses may require more frequent worming, than a horse that exhibits a strong immune system and lower shed rate.

It is thus important, especially if you are managing a boarding or breeding operation, that you know which horse requires which program. With a F.E.C.T. you will also know which wormer to use, and won’t waste your hard-earned money on wormers that are not needed and do not solve the specific parasite problem. You may be diligently worming your horses every 6-8 weeks and in actuality only need to worm them twice a year.

Note that you will still need to paste worm for bots and tapeworms in Spring and Fall, as the fecal testing is aimed primarily at counting eggs from ascarids (roundworms), and large and small strongyles (bloodworms).

Thanks to the advent of Ivermectin, the large strongyle worm population has seen a huge decrease in the U.S.A., which is great as their ability to cause significant mucosal damage in the gut is well documented. However, the small strongyle is showing resistance to wormers, so it is imperative that we keep a watchful eye on our herd for these worms. As a breeder I know that foals and young horses and even pregnant mares are very susceptible to both the ascarids and small strongyles.

Of course once you have treated your horse, how do you know if it worked? Or whether the worms he harbors are resistant to the particular wormer used?
You must retest the horse to know. I like to call it: “Test. Treat. Test Repeat.”
Also known as Fecal Egg Count Reduction Test (F.E.C.R.T.) in veterinary terms.

As a horse owner I don’t want to go to the expense of calling out my vet every time I want to do a F.E.C.T. Thankfully, the option of a simple mail in sample testing kit is readily available, with results sent to your email account. I spoke with expert Dr. John Byrd, D.V.M., who is the founder of Horsemen’s Laboratory based in Illinois, to find out more about his company and what services they offer.

“Our mission at Horsemen’s Laboratory has always been to provide an easy, simple to use and effective equine fecal worm egg count program for the horse owner. Over the years I have seen many changes in equine parasitology. As an experienced veterinary surgeon have advised thousands of clients on how best to address the issues of worms in horses to prevent disease and illness. I saw a need for the horse owner to have a handy, easy to use and affordable method for taking their own equine fecal samples and having them tested at a reliable laboratory. Not just that, but to additionally provide advice on results as needed as to how to treat a worm count that may exist and how best to monitor the results of the treatment. So I provide a professional consultation service to our clients in addition to worm count results from our laboratory.”

Horsemen’s Laboratory handles the ‘business end’ of the worm count industry for many retailers as well as end users. For myself, going directly to the source seems a smart choice. Especially when I can talk directly to an experienced vet whose specialty is in the field of equine parasitology. And I can add from first hand experience, Dr. John Byrd is extremely easy to talk with and explains things in an accessible manner. You come away from the conversation with a sense of comfort with the knowledge you are taking an intelligent approach to handling your horse’s parasite management. You also know that you are not contributing to the unsustainable practice of routine calendar over-worming and taking responsibility as a horse owner for your share of the problem in the horse community.

What constitutes a heavy shedder for example and why do some horses always shed high worm egg counts throughout their lives? What should I do about it?
As a competitor, when my horses travel, should I worry about elevated worm counts? The answer is yes.

Do I need to keep my horses inside for a day or two after worming so they are not shedding worms onto the pasture? The answer is no.

When a new horse arrives on my property is giving it a wormer on arrival enough? Well you get the idea. We have questions and Dr. John Byrd has answers.

“I recommend that horse owners conduct a fecal equine egg count for their horse and then treat if needed with a wormer that will target those particular worms. Two weeks after treatment test the egg count again. If you have resistant worms hosted by one of your horses you will know and be able to deal with the issue. Many horses are over-treated with wormers, and it is an expensive and unnecessary habit.,” explained Dr. Byrd.

Using a Horseman’s Laboratory sample kit is as easy as 1,2,3. Visit www.HorsemensLab.com for more information and take control of your horse’s parasite health today. You can literally, count down to a successful equine deworming program.