Deworming advice

[Small_Change]

I have an older TB gelding in the barn who seems to have a consistent worm burden, and I was hoping to get some evidence-driven advice on what to do with him please. We’re in Southern Ontario, and deworm based on fecals. Everyone else has a negative fecal.

He came to the barn in 2022, and had a strongyle count of 1600 that spring. We dewormed with moxidectin in April, pyrantel in July, ivermectin in August, and moxidectin/praziquantel in November that year. In spring of 2023, his egg count was down to 525, and we dewormed him with moxidectin in April, then moxidectin/praziquantel in November. This spring, his fecal count is 275. We’re making progress, but I want to be sure that there’s not something I can do better here! I did ask for advice from his vet, but I think it was generic rather than specific based on what I’ve used on this horse and his numbers.

I sincerely appreciate any thoughts and advice

[OzarksRider]

Has he been tested for PPID?

[NaturallyHappy]

I was going to ask that, as well.

[Rel6]

Are you redoing the fecal 2 weeks after deworming to make sure the worming is effective?

My horse is a naturally high shedder. I pull a fecal every 6 months and deworm in accordance with that. If the number is high, we pull another fecal 2 weeks after deworming to make sure that comes back at zero. My horse’s spring number is always high (anywhere from 400-900) but back to zero after deworming, and always low in the fall. My vet isn’t concerned.

It sounds like you’ve got it under control already. 275 is considered a moderate shedder, and even 525 is barely ticked over into high. I would just want to make sure your horse is responding to the dewormer and not carrying that burden year round.

[Simkie]

The AAEP recently updated their deworming guidelines, which might have some new ideas or info for you:

Internal-Parasite-Control-Guidelines_May-2024.pdf

I found this fascinating…

“The environmental control of strongyles using nematophagous fungi delivered to horses in feed
has shown promising results (Healey et al., 2018), and a product is now available in North America.”

Here’s the paper that’s being referenced:

https://www.sciencedirect.com/science/article/pii/S0304401718300591

And the product…

Studies - Duddingtonia Flagrans - Efficacy

BioWorma®

But wow, how incredible IS that?!

[OzarksRider]

Great minds think alike

[jlm0305]

@Rel6

It sounds like you’ve got it under control already. 275 is considered a moderate shedder, and even 525 is barely ticked over into high. I would just want to make sure your horse is responding to the dewormer and not carrying that burden year round

FEC does not correlate to worm burden. Those results are telling you how much your horse is contributing to infection pressure on pasture, not how many worms the horse has.

A count of 900 epg isn’t particularly high and it’s really, really important to remember that the goal is not to completely remove all worms because that is not going to happen. The goal is to help prevent any of the very rare issues resulting from high worm burdens and reduce infection pressure on the pasture.

@Small_Change that pyrantel was likely ineffective if we are talking about strongyle counts. It’s important to do the FECRT because we’ve got so much resistance in horse parasites, but it sounds like what you are doing is working fine. Don’t be shocked if counts go back up - a lot of horses tend to stay at the same FEC level their whole adult lives.

[Rel6]

@jlm0305

FEC does not correlate to worm burden. Those results are telling you how much your horse is contributing to infection pressure on pasture, not how many worms the horse has.

A count of 900 epg isn’t particularly high and it’s really, really important to remember that the goal is not to completely remove all worms because that is not going to happen. The goal is to help prevent any of the very rare issues resulting from high worm burdens and reduce infection pressure on the pasture.

The FEC measures eggs shed per gram of manure (EPG). Over 500 indicates a high shedder. The goal isn’t an FEC of 0 year round, but there should be 0 two weeks after deworming, and otherwise can indicate resistance. That was my point - if the horse is carrying a steady burden year round, without a significant response to the dewormer, that is a resistance issue. And OP can catch that by doing a fecal 2 weeks after deworming

[JB]

Bioworma has been out a few years, and is quite expensive, at $2-2.50 per day per horse, and all horses on the farm need to be on it. Not horrible if you have 2 horses at home, but more than that…

It IS a great thing, but the cost will have to come down, a lot, for it to ever be in widespread use.

@Rel6

there should be 0 two weeks after deworming

Not necessarily. The FEC reduction % isn’t ever 100%. Here’s a chart showing the desired reduction % to determine no resistance likely

How to find out if your horse's dewormer is working

[Rel6]

Generally a zero indicates no eggs per gram identified. It depends on the sensitivity of the test, but that may not mean none exist, just that there are so few as to be unidentifiable. If your horse has 300 EPG before deworming, and you eliminate 96%, you’re left with 12 EPG - which may result in a reading of 0 EPG. For sure if you arr starting at 1200 you may not get that result.

Two weeks after deworming fecals I’ve pulled have always shown 0 EPG - which like you mention may not actually reflect 100% reduction but rather 96%+ reduction.

[JB]

I found a thread in a FB group from 2019 on Bioworma. It was still Premier1 who carried it then, and the price has come down a bit, thankfully. Still quite a hefty chunk of change if you’ve got more than a couple of horses though

@Rel6

Generally a zero indicates no eggs per gram identified . It depends on the sensitivity of the test, but that may not mean none exist, just that there are so few as to be unidentifiable. If your horse has 300 EPG before deworming, and you eliminate 96%, you’re left with 12 EPG - which may result in a reading of 0 EPG. For sure if you arr starting at 1200 you may not get that result.

yes, exactly, you may get 0, but you may get 1-12 (in your example). It’s just misleading to say you should get 0. 98% reduction when starting with 3000 is 60, which is reasonable to be able to count

[jlm0305]

@Rel6

Over 500 indicates a high shedder.

Yes, but it’s nothing to panic about nor is a 900 epg count because it’s not particularly high. The numbers we choose for low/medium/high shedders are arbitrary.

A steady burden year round is not necessarily a resistance issue. It’s perfectly normal for counts to go back up after a few months - that’s why higher shedders are treated more frequently. Only reduced percent reduction post deworming indicates a potential resistance issue. Dr. Ray Kaplan and co recently published FECRT guidelines via WAAVP to help determine all of this. Macrocyclic lactones have reduced egg reappearance periods in many places and in some cases that period is as little as four weeks!

@Rel6

Generally a zero indicates no eggs per gram identified

Yep. Another reason not to attempt to correlate count and burden, and to pay attention to who is doing your counts as well as how. Because the total number of eggs being counted is important for FECRT too! When using methods with higher multiplication factors (not the same as sensitivity) it’s important to ensure enough total eggs are counted to do the FECRT in the first place.

[Rel6]

We’re saying the same thing - I don’t think anyone said anything about panicking. I specifically said I wasn’t concerned

I think you’re missing my point about a steady burden. If you’re deworming and not seeing a decrease at all, that could indicate resistance. If you’re deworming and seeing a significant decrease on a repeat fecal two weeks out, and then the number goes back up and holds steady, that is different.

[jlm0305]

@JB

It was still Premier1 who carried it then, and the price has come down a bit, thankfully. Still quite a hefty chunk of change if you’ve got more than a couple of horses though

You don’t necessarily give it year-round though, only when egg hatch rates are highest. There’s some really awesome EM images of the fungi trapping the nematodes too. Some make little lassos!

It’s decently popular in the small ruminant crowds.

[jlm0305]

Semantics really matter though, and a lot of people do panic over a “high” count. I encountered it a lot while doing my PhD and talking to people about deworming their horses. Same thing with stating a steady year-round burden - that’s not the same as reduced efficacy two weeks after deworming and can confuse people.

[Rel6]

Sure, which is why I specifically said that it sounded like OP had it under control and I wasn’t concerned about my horse being a high shedder. Not sure where semantics come into that - it’s pretty clear.

But if we’re talking semantics, what I said was “if the horse is carrying a steady burden year round, without a significant response to the dewormer, that is a resistance issue.”

Didn’t come here to argue about this, so I’ll leave you to it from here!

[JB]

@jlm0305

You don’t necessarily give it year-round though, only when egg hatch rates are highest.

right, but for a lot of the country, that’s a lot of months Here it would be around 7 months, and that increases the farther south you go. 3 horses x $2.50/day is already $225/month. And actually, it would be a bit more as one of mine is closer to 1400lb than 1200.

[Small_Change]

Thank you very much everyone! I appreciate the reassurance and additional info. I just wanted to be sure there wasn’t something I was missing as he is the only one I have on the property with anything on his fecal (and I do understand that the fecal is just a snapshot, etc). The horse is a boarder with me, so I will pass along the info regarding a post deworming fecal. The owner is planning to do PPID labs in the fall as he has a few other things that point to that maybe being an issue as well.

Thanks again!