Dr. Abby Sage on Deworming: What Horse Owners Need to Know (AAEP Update)

Pegasus Co-Founder Jen Tankel is joined by Dr. Abby Sage, VMD, MS, DACVIM, Equine Technical Services Veterinarian with Zoetis.

As deworming practices evolve, what horse owners think they should be doing may no longer be best practice. In this episode, Dr. Sage breaks down the latest American Association of Equine Practitioners (AAEP) guidelines and what they actually mean for your horse. From why “more dewormer” isn’t always better to how fecal egg counts are changing the game, this conversation covers the science behind smarter, more targeted parasite control so you can make informed decisions heading into the grazing season. 

Have you ever wondered, “how much dewormer does my horse actually need?” Healthy adult horses may need less than you think. But not all active ingredients are the same. Use Quest® Gel, with moxidectin, for the early grazing season, and Quest® Plus Gel, with moxidectin and praziquantel, for the late grazing season. Visit ZoetisEquine.com for more deworming resources. Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism. 

About Zoetis Equine: 

• Guest: Abby Sage, VMD, MS, DACVIM, Equine Technical Services Veterinarian, Zoetis 
• Website: Learn About Targeted Deworming 
• YouTube: Worms of Concern Rap Song
• AAEP: Updated 2024 Deworming Guidelines 

IMPORTANT SAFETY INFORMATION 

Do not use Quest Gel or Quest Plus Gel in foals less than 6 months of age or in sick, debilitated and underweight horses. Do not use these products in other animal species, as severe adverse reactions, including fatalities in dogs, may result. Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism. 

References 

1. American Association of Equine Practitioners. 2024 Revised AAEPinternal parasite control guidelines. https://aaep.org/post/aaep-publishes-updated-internal-parasite-control-guidelines/. 
2. Young A, Finno C. Intestinal Parasites in Horses. School of Veterinary Medicine, University of California, Davis. August 12, 2022. https://ceh.vetmed.ucdavis.edu/health-topics/intestinal-parasites-horses. 
3. Mason ME, Voris ND, Ortis HA, et al. Comparison of a single dose of moxidectin and a five-day course of fenbendazole to reduce and suppress cyathostomin fecal egg counts in a herd of embryo transfer-recipient mares. J Am Vet Med Assoc. 2014;245(8):944-951. 
4. Reinemeyer CR, Prado JC, Nielsen MK.

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Transcript

How Much Dewormer Is Needed

SPEAKER_02 0:00

Have you ever wondered how much dewormer does my horse actually need? Healthy adult horses may need less than you think, but not all activate ingredients are the same. Use quest gel with moxidactin for the early grazing season and quest plus gel with moxidactin and prosequantil for the late grazing season. Visit Zoettistecoine.com for more deworming resources.

SPEAKER_01 0:26

Important safety information do not use Quest Gel or Questplus Gel in foals less than six months of age or in sick, debilitated, and underweight horses.

Meet Dr. Sage

SPEAKER_02 0:36

Do not use these products in other animal species as severe adverse reactions, including fatalities in dogs, may result. Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism. Dr. Sage has a veterinary degree from the University of Pennsylvania and is board certified in large animal internal medicine. She was on faculty at New Bolton and the University of Minnesota before joining Zoetis, and she's published numerous scientific papers on equine internal medicine, ultrasound, and cardiology. So, Dr. Sage, thank you so much for joining us. Well, thank you, Jen. Thanks for having me. So we'd love to kick it off to learn more about your background and how did your path lead you to equine medicine.

SPEAKER_00 1:55

Well, uh, I always wanted to be a veterinarian, uh, ever since I could really know what a veterinarian was. And I always thought I'd be a cat veterinarian, actually. But my sister, she had the horse gene. She loved horses, and so had I had to go to the barn with her. Uh so I ended up loving horses and riding and uh carrying that through through all my teenage years and into college. Um, but I still thought I I would end up being, I didn't know any horse vets that were women when I was coming up. And so I didn't really think I could be a horse veterinarian. And then I was in vet school, and it was really my our first year, they had seminars for, you know, different veterinarians from different uh walks of life. And we had a very small woman come in and talk about how she was a horse vet, and that was it. I was a horse vet from then on. Oh, right. Well, so do you have your own horse as well? And do you ride? Yes, I do. Actually, my daughter and I have our horses at our house. And so we are now uh trail riders. I did lots of the showing before, but now we're tour riders. We use we go to all the state parks in Virginia, which are absolutely beautiful, and uh, we spend a lot of weekends together riding, so it's really fun.

SPEAKER_02 3:10

Yeah, so you yeah, you're in a great spot for that. So when you went out with your sister, inevitably you got the bug yourself.

SPEAKER_00 3:17

Totally, totally. Uh even more so than she did. She doesn't ride anymore, but for both of us.

SPEAKER_02 3:23

Well, so can you also share uh what it is that you love to do outside of work life as well, but in addition to riding?

SPEAKER_00 3:29

I'm a big traveler. I like to travel. And so um I do that a lot for my job, but I also on vacation try and see as much of the world as possible.

SPEAKER_02 3:38

Gotcha. Okay. So what do you love about working within the equine industry and really the equestrian community?

SPEAKER_00 3:44

You know, for me, it's been kind of a journey. I started off as a veterinarian and did a residency and then stayed in academics for much of my career. And then I ended up in private practice. And following that, I worked for state government and now in corporate. So I feel like I've really seen a lot of the equine industry. And I think, you know, from each of those different vantage points, you meet so many amazing people who who do everything for the love of their horse and really have the horse's welfare always in mind. So it's been a really great career I've had. I've gotten to really see so many parts of what all these people are for helping their horses. And it's it's an amazing group.

The Biggest Deworming Myth

SPEAKER_02 4:28

Yeah, totally. Well, so since we are going to be talking about deworming and um, you know, fecal matter, so to start off the topic of deworming, are there any common misconceptions?

SPEAKER_00 4:40

Yes, I think we have been for many, many years just told that we should just buy dewormers at the, you know, our our farm stores and that that would rid us of parasites. And really that is not the goal of deworming at all. The goal is not to rid your horse of parasites. We're not gonna, no dewormer can totally get rid of all the parasites that a horse has. And really the goal now is to just decrease the amount of adult worms in the horse and the amount of contamination on the pasture. So that's a myth that I grew up thinking was the way it was, and we're glad to be able to to kind of change that perception for people.

How Fecal Egg Counts Help

SPEAKER_02 5:22

So, how do you know if there is supposed to be some, you know, bit of um, you know, like the stuff in there? How do you know like what's a good amount versus what's not a good amount?

SPEAKER_00 5:31

Of of parasites, you mean?

SPEAKER_02 5:33

Yes.

SPEAKER_00 5:34

Yeah, so we recommend that you do a fecal egg count once a year. Your veterinarian will work with you with this, and this allows you to know if your horse, how many eggs that your horse is shedding. It doesn't tell you the amount of parasites. Most adult horses have immunity to their parasites to some point, and they are able to manage a parasite load. A huge load would be an issue, but your average horse is fine because over time they develop immunity. Fecal egg count, what we're doing is we're finding out which horses are actually responsible for the most amount of eggs on the pasture. And then we're going to target those horses.

SPEAKER_02 6:14

Okay, so and can you give us an overview of the current guidelines for deworming horses and why we've seen changes in the recent years?

SPEAKER_00 6:23

Yes. So the reason we've seen changes is because we are starting to see resistance to our dewormers. To my knowledge, there are no dewormers that will be coming in the near future from any company. And so we have to live with the dewormers that we have. And just like antibiotics, dewormers also can, or parasites can also develop resistance to dewormers. And so we want to prevent that from happening by using targeted deworming. And what this means is we're going to only deworm twice a year for adults, horses in the spring, and then again in the fall. And then we're going to do a fecal egg count to tell how which are the horses that are the highest shedders. We're going to target those horses for additional deworming. Uh, usually up in the north, you would do an additional time in the summer, more down in the south, you would do two more times in the in the summer to for a total of four.

SPEAKER_02 7:18

Is that um difference of location just simply because they're up north, there's there's more snow? So for you know, being in Connecticut right now, no one's grazing at the moment. We're covered in snow. So is that kind of the the rationale for why it's a different schedule depending on where you are in the country?

SPEAKER_00 7:35

Exactly. The grazing season is longer down south. So that means horses, once they're dewormed, will have a longer time to start shedding more eggs. And so it just de kind of decreases the amount of eggs that they're shedding by adding an additional deworming for those horses.

SPEAKER_02 7:52

Gotcha. Okay, and so when you say resistance, can you explain more about how that actually happens?

SPEAKER_00 7:58

Yes. So what happens is when you deworm a horse, then a lot of those adult parasites die off and then they are gone. But some will not. Some will survive that deworming and they will shed eggs and then they will produce larva, which then go back into the horse. And so those then become the resistant worms. So the more we deworm with a lot of different dewormers, the more we're choosing those resistant parasites. And this happens over a long period of time. It doesn't happen every time we deworm. It's sort of a very slow evolving problem. But we have seen this over the last several couple decades that we're starting to see this resistance uh come up to, especially the older dewormers, the ones that were first on the market, those that have come more recently, such as ivermectin and moxidectin, those have less resistance, but we don't want to you overuse them so that you know we're going to end up with resistance to those as well.

SPEAKER_02 9:02

There is such a thing as overusing it. Is that right?

SPEAKER_00 9:05

Yes. So it's not necessary, as I said before. Most horses do tolerate their adult worms very well. Uh it's our our younger horses that we deworm more frequently, but if they're dewormed on a regular schedule, they'll be fine as well. But our adult horses don't need to be dewormed every few weeks. Really, twice a year to get rid of the um adult worms and the tapeworms. Our most concern is small strongiles and tapeworms in adult horses. And so twice a year is enough to keep those at bay for most horses.

Interpreting Low And High Shedders

SPEAKER_02 9:37

Gotcha. Okay. And so we mentioned this before, but um, so tell us a bit more about fecal egg count tests and how they work and why they're so important.

SPEAKER_00 9:46

So the reason that we should do them every year on every horse is that we need to identify which horse is going to be shedding more eggs onto the pasture. So you would collect manure from each of the horses that are in your care and take those to a veterinarian. The veterinarian will just run a simple test. They do what's called a flotation, and we'll be able to determine the number of eggs per gram in the feces from each horse. And based on that, they will categorize them as a low shedder, a medium shedding, or a high shedder. High shedders shed over 500 eggs per gram. Low shedders are 200 or less. And where we're what we're really going to target is the high shedder, because they're obviously putting more eggs on the pasture. Those eggs then become larvae in the manure, and then that larvae gets picked up and ingested by horses that are grazing. And therefore, the more larvae you have, the more of a worm burden you'll have for all of those horses. So we pick out those high shutters so that we can target them, decrease the worm burden for everybody on the pasture.

SPEAKER_02 10:53

That's so interesting. So if you do have a high shutter, is that one of those things where you'll just target through the dewarmer, or is it also a good practice to maybe separate them from the low shutters, or is that getting, you know, two in the weeds?

SPEAKER_00 11:05

Yeah, that's two in the weeds. That's why we recommend, you know, horses have to be put together for a lot of reasons, and deworming or worm burden probably shouldn't do one of those. So by by giving them extra doses of dewarmer throughout the course of the year, you are basically turning them into a low shutter, if you will. They're not going to be shedding as many eggs as everybody else. So they can stay on the pasture with everyone else. Um, you're just decreasing the amount of eggs that they're going to be shedding over that course of time. Gotcha. Okay.

SPEAKER_02 11:35

And so when I go to buy a dewormer, what would you recommend a horse owner look out for?

SPEAKER_00 11:40

Well, you want something that's broad spectrum. As I said before, we have the two main parasites that were of most concern in the adult horse are small strongiles and tapeworms. So what we do is we target small strongiles both in the spring and in the fall with our dewarmer. So we want to get a dewarmer that certainly will target small strongyles, but also there are other worms that we want to consider, like bots, uh, pinworms, and threadworms. There's a number of them. So you want a broad spectrum dewarmer that will hit all the main worms. And then in the fall, we target tapeworms with our small stronggeles. So spring, we worry most about small strongyles. Fall, we're gonna worry about small strongyles and tapeworms. And generally, we're gonna look for a drug such as ProsyQantal that is in addition to our drug for small strongiles. So let's say for us at Zoetis, we make Quest. Quest is moxidectin. Moxidectin is a very broad spectrum uh dewormer, and it will it will get all of those main worms. And then in the fall, we have Quest Plus, which is moxidectin plus prosiquantal, and that will get the tapeworms as well as all of the small strongyles.

SPEAKER_02 13:00

Okay, so to clarify, so moxidectrin is the specific ingredient that you would want to that you recommend when you buy a dewormer.

SPEAKER_00 13:07

Yes. And the reason we may, you know, have moxidectin is because in addition to just getting the adult worms, it also gets the worm, the larvae that are insisted in the mucosa in the intestine. And so we want to get rid of all of those and the adult worms, and moxidectin will do that as well. So, yes, that's what we would look for. Another broad spectrum is ivermectin. It does not do insisted small stronggeles, but it will get a large variety. So when we choose an ingredient, we want to pick something that is broad spectrum, and there are a lot of them out in the market. Those that have been on the market longer have more resistance. Uh, moxidectin and ivermectin have been on the market for the least amount of time, so they have the least resistance to them. In my opinion, moxidectin has a little advantage in that it will get the insisted strongiles, whereas ivermectin only gets the adults.

SPEAKER_02 14:05

And when you're buying a dewormer, is it one where you want to buy the same one every single time, or is it good to essentially have a rotation?

SPEAKER_00 14:13

You don't really need to have a rotation. Um, that used to be the thought, we'll just kind of blindly rotate them and just use different ones. We didn't even know that we were developing resistance and that we weren't really killing off the worms because we were constantly changing it and and we were developing more resistance. We recommend just twice a year deworming with the same dewormer. And of course, in our case, we're recommending moxidectin, um, and you don't need to really rotate.

SPEAKER_02 14:45

Okay. So, in addition to the time of year, especially depending on where you live in the country, are there any other timing tips that you have for horse owners?

SPEAKER_00 14:54

Well, you know, horses, adult horses, especially, really tolerate deworming fine. They really don't really have any problem. I wouldn't recommend doing it right before you're going to go to a show or go on a long ride, you know, trail ride or trailer ride is what I mean. But um, really, for the most part, there really are very few side effects to that. And one other thing I just wanted to mention is that all of these things that I'm talking about are all part of the AAEP guidelines. The AAP is the American Association of Equine Practitioners, and that is the largest association of equine veterinarians in the country. And they publish guidelines every year about, you know, regularly, I shouldn't say every year, but regularly on different topics. But deworming, they just had um their guidelines come out in 2024, their updated guidelines, and those that is, you know, all of these things I'm recommending are based on those guidelines.

SPEAKER_02 15:48

Cool. All right. So we'll include those in the in the in the show notes. Um, and then because we do have a lot of listeners that do compete, so say there is a show at the end of the month. Is there, do you have a typical window of when you would say this is kind of your minimum time before you give your horse a a dewormer?

The Buy Less Dewormer Campaign

SPEAKER_00 16:06

No, I just probably wouldn't do it two or three days before the show. Other than that, I think it's totally fine. I wouldn't really worry too much about it. Horses really don't get too stressed by it. Perfect.

SPEAKER_02 16:18

Okay. So touching on Zoetis' campaign, because Zoetis does a lot of really awesome campaigns. So I saw the Buy Less Dewormer campaign. And could you share more about that for the listeners too?

SPEAKER_00 16:29

Yeah. So the whole point is again that we're not just blindly buying dewormers and deworming every six to eight weeks, that we're actually finding out which horses we need to deworm more often. And we're just going to deworm twice a year. Again, this is based on AAP guidelines. We want to, so we're going to buy less dewormer because we're only going to be, you know, choosing to deworm mostly twice a year. And in addition, there are some other dewormers that will get the insisted stronggels. Um, that's one is called panicure. That one has um, it takes five double doses for that to work. Moxidectin, we have the same, it has the same results with just one dose. So that's part of the buy less dewormer campaign as well. Gotcha.

SPEAKER_02 17:15

So beyond even selecting a dewormer with your vet, what can we as horse owners do to help lower our horses' exposures to parasites?

SPEAKER_00 17:22

I think it's very important to think about the environment, especially because we know that we're getting resistance. And so we don't want to just use a chemical and think that that's gonna solve all of our problems. And as a as a whole group, an industry, we need to really be thinking about protecting our our horses, our the herd, if you will. And so environmental uh cleanup is very important. So the life cycle of parasites are that they will shed, the adults live in the intestine, they will shed eggs. Those eggs sit in the manure, and under the optimum conditions, meaning on a nice warm day, uh they it takes about three days for them to develop into larva that can then infect the horse again. And horses can get reinfected. So environmentally, if we can collect that manure on a every three days or twice a week basis so that it is not sitting in the pasture, then we are not exposing our horses to that infective larva. When people drag the fields, that is helpful because it breaks up those manure clumps and then the sun will get to it and drying and it'll kill off those larva. And so a lot of people do that. I think most people don't do it often enough. So we want to do that probably at least twice a week. Um, ideally, you would actually remove the manure, but if that's not possible, then dragging the fields at least twice a week would be best. And that's just to help us prevent resistance, both on your farm and then throughout the horse industry.

Takeaways And Vet Conversations

SPEAKER_02 18:54

Yeah, it's another good reason to drag consistently in addition to all the other benefits. And I know that because again, like because we are horse show software and we have a lot of listeners that participate in horse shows, oftentimes you'll hear grumblings about some, you know, riders that might leave their manure and the that the cross ties and they just don't clean up after themselves. Let this be a really good reminder that it's not so much even about, I mean, yes, of course, it's about being respectful and you know, cleaning up after yourself, but also it is uh it can breed more parasites and be really problematic for your horses. So let that also be something that fuels everyone to pick up after their horses at the war shows. It's really helpful. So because it is it is so timely to speak with you on this topic, are there any other takeaways that you hope listeners walk away with?

SPEAKER_00 19:44

Yes, I just hope that people will spend a little more time thinking about dewarming than we have in the past, uh, having a conversation with their veterinarian. The, you know, time of spring vaccines is a great time to have that conversation with your veterinarian about should I do a fecal egg count, what is going on with my particular situation? Because, you know, some people have huge fields with few horses, and that's a different story than having small fields with lots of horses. So we all have different ways that we manage our horses. And I think our veterinarian is the person who has the most knowledge who can guide us on what is the best deworming program for us.

SPEAKER_02 20:27

Gotcha. And then so anything else too with the listeners? You've been so helpful with all of the different things to think about and timing and ingredients and things like that. But any other key takeaways before uh I let you go?

SPEAKER_00 20:39

I think we've pretty much covered the topic, Jen. So thank you very much for giving us this opportunity. I will say that uh we do have a great website at Zoetis. It's at Zoettisequine.com. It has lots of infographics about dewarming. It talks, we didn't talk much about dewarming foals and yearlings, but there's lots of information on there. There's, you know, we talked about those different zones where you, you know, if you're in the north or the south, there's maps there, lots of easy uh things for you to follow along. So I'd say to the listeners, you know, take a look at that and see if they can find things that would be helpful for them.

SPEAKER_02 21:15

Perfect. Okay, yeah, and we'll link all of that in the show notes as well. So all right, well, Dr. Sage, thank you so much for all of this insight. And yes, for our listeners, SOAS is so passionate about proper deworming that they've even deemed March Fecal Health Month and have a variety of learning materials, just as you mentioned, including Worms of Concern rap song, which I haven't actually listened to yet, but I'm looking forward to hearing that. And a website with the product quiz and lots of helpful resources as always. So we'll share all of those links in the show notes. And um, yeah, thank you so much for for jumping on, Dr. Sage, and sharing all this information with us. Well, thanks for giving us the opportunity.

SPEAKER_01 22:04

Important safety information. Do not use Quest Gel or Quest Quest Gel in foals less than six months of age or in sick, debilitated, and underweight forces. Do not use these products in other animal species as severe adverse reactions, including fatalities in dogs, may result. Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism.