Parasite burden and Vitamin E levels

If a 6-year-old horse has a consistent parasite burden of 500-700 EPG (McMaster’s I believe–not my horse) for a couple of years, would you expect that to significantly affect their Vitamin E levels?

I know that high parasite burdens can affect nutrient absorption and digestive function, but would you expect that at the levels mentioned?

Owner is working with vet to reduce parasites. Her boarding stable was over-deworming on a set rotational program in the past despite pulling regular fecals, and may have a bit of a resistance issue now. Quite a few horses are supposedly having the same problems. Pasture management is also being reconsidered I believe.

500-700 is technically high, but it’s not HIGH in terms of having seen 3000 (in a mini, no less :open_mouth:)

Could it affect E? Maybe? I don’t know if it’s high enough to cause permanent damage.

Are you saying these horses have tested low levels of E? As we are coming out of Winter, what was their Winter diet like:? How much pasture are they on (lushness, not acres), for how many hours a day, on a regular basis, from Spring to Fall?

I believe the horse gets either 4 or 6 hours of turnout on not-super-lush pasture. The issues started in winter when pasture wouldn’t provide much Vitamin E anyway. She’s already getting supplemental Vitamin E but I don’t know how much or what kind.

This is my friend’s horse, who has been having issues since February that haven’t been diagnosed yet despite seeing some of the best experts at one of the top vet hospitals and doing extensive diagnostics. She told me that the vets want to get her parasite burden down so vitamin E goes up, and at that point they will hopefully be able to figure out if it’s a “muscular disorder tied to vitamin E deficiency.” EDM?

I was curious because I didn’t think parasites on the low end of high would have that big an impact, but maybe if it’s been going on a while and the horse is vulnerable in some other way? When I first moved my horse home from that same boarding facility his fecal showed 1550 EPG! So 500-700 didn’t seem crazy high to me. (My guy has been consistently negative for years now, yay!)

My guess would be that the chronically low intake of lower quality grass, combined with hay-only Winters, combined with what’s often too-low E supplementation, finally caught up

And, some horses simply seem to have higher than normal requirements for E to maintain healthy levels, or need to be on the high side of normal to be happy

How many times has this horse been fecal tested to show a high load?

This spring she was 500 and the previous two springs she was 700. I don’t know if how much testing was done in between…

Thanks for your answers!

It’s possible she has naturally lower immunity, naturally higher nutrient needs at least in some areas, that those are what’s causing the high counts, as opposed to the other way around.

I know it’s not your horse, but it would be really good to know what drugs were used, when, during these last couple of years. I wonder (hope) if it’s a matter of just never using anything effective enough, as opposed to having created a resistance issue. Resistance issues don’t end up in 1 horse, they end up in all the horses who occupy the same pasture space, eventually, since that’s where the resistant strongyle eggs are laid, hatch, and are eaten

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Right, so since there are numerous horses at the barn with persistent, high parasite burdens that’s why I wonder if there’s a resistance issue? But hopefully it’s just poor deworming…unfortunately I don’t know the details. I’ve already encouraged her to post on here because I think the hive mind could be helpful re: this horse’s issues, but we’ll see.

Oh, gotcha, I must have missed that. I HOPE it’s just that they’ve been using ineffective products and not not not that they have created a resistant colony :expressionless:

If it ends up they have created a macrycyclic lactone resistant strongyle population, then a recent situation on a KY farm who had imported Irish TB yearlings with a highly resistant population where a combo of moxidectin, oxibendazole, and pyrantel pamoate was needed, that may be something that has to be done. Meaning, at one time, Quest + Anthelcide + Strongid, all based on the horse’s weight.

So their website mentions “a regular de-worming schedule using a rotation of Panacur, Ivermectin and Strongid,” but I don’t know if that’s up to date or what the rotation schedule was.

I’m 99% sure I know the barn you’re talking about (because I’m 99% sure I know this horse), and the barn just switched from rotational deworming (every 2-3 months or so) to targeted FEC-based deworming this spring. As far as I know, they have done rotational deworming for years at the advice of their vet {sigh}. High shedders this year were (I think) given a panacur power-pack, and were re-tested for efficacy (but only them - I don’t think anyone else was re-tested). Admittedly I am not fully in the loop because my horse is a consistently low-shedder (and since having moved there I was on my own program based on fecals and deworm accordingly… except when they “forget” I’m on my own plan and deworm my horse for me :woman_facepalming:).

So it would not surprise me if there was some degree of resistance on the farm, especially considering how overgrazed, not dragged (drugged?), and not rested the fields are.

Long story short: I think the website is probably not up to date :slight_smile:

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Hi Libby2563,

In my experience, it depends on the rotation schedule, pasture management and the use of each wormer. Ami was “patient zero” at the farm she’s now at (over 1400, I believe), despite a rotating worming schedule her whole life. The horse I have now which came from that farm was “collateral damage” (over 1200, I believe). In both cases, I believe we did a 5-day dose of Panacur (the Power Pack - it is so safe), discontinued the strongid (safe but many bugs are immune to), then hit with Ivermectin/praziquantel. Ami’s load was halved and she needed a second round of drugs. Fior’s load came down to 400 and we managed it by only using Ivermectin + Praziquantel (why not - prazi is soooo safe) and moxidectin + praziquantel. I now only use Ivermectin + prazi and Quest. Subsequent fecals were really low for years and we stopped doing them. That said, there is going to come a time where bugs get immune to ivermectin and moxidectin. Unfortunately I don’t think there is anything in the pipeline for when this occurs.

There isn’t. Parasitologists have been saying for years we’ve got to start researching new treatment options and the response from funding agencies tends to be that we’re overstating the problem. I’m currently submitting a proposal to look at a possible new drug target, so we will see if they have finally decided it is worth funding.


Cool! Good luck!! Can I ask what your drug targets?

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I messaged you!

The only reason “why not” is that over-use will eventually contribute to resistance in tapeworms.


I just read a study on a dead probiotic (coated in something? I need to go read it again) which did a phenomenal job killing ascarids in foals, so that’s promising. Hopefully something like that exists somewhere for strongyles too.

Ah yes, Cry5B. That study sent me to the ER, hah.

It is effective, but the main issue is that the dose is absolutely massive. The dosing rate was 30 mg/kg via nasogastric tube of a really thick, goopy substance that had to be kept cold. It was extremely difficult to get it into them, and it was a LOT. Based on their weight, each foal was given about 5 grams of the stuff, which was quite a bit of volume and it had to be mixed with water to get it thin enough to even go down the tube. For reference, Panacur is dosed at 10 mg/kg in foals. Also keep in mind that this was using a nasogastric tube, rather than oral administration. The big issue with it is whether it can make it to the worms in the small intestine without breaking down. Making a coating to protect the protein is really expensive, but there’s a study starting this summer looking at using it in strongyles (large intestine, so even more difficult to get it there) and attempting to get enough data for a grant proposal to look into testing different coatings. Hopefully it works out, we will see. It’s certainly promising!


Here’s the study I was referring to:

An inactivated bacterium (paraprobiotic) expressing Bacillus thuringiensis Cry5B as a therapeutic for Ascaris and Parascaris spp. infections in large animals - ScienceDirect

this did make it through and kill very effectively

Fecal egg counts persisted in all foals in the control group up until and including day 14 and in three out of four foals throughout the entire duration of the study. In contrast, fecal egg counts went to zero in all Cry5B IBaCC-treated foals at the first sample taken one-week post-treatment and stayed at zero for all treated foals throughout the study.

I agree the dose used makes it difficult to use for paste deworming, but I’m sure (I hope!) they will be able to find a lowest effective dose, and then figure out how to package it for ease of use.

I HOPE this also means they are this much closer to finding something similar for strongyles, which is a much bigger issue.

We are still a long, long way off from an approved, marketable drug. It will likely take at least a decade. That’s the problem with people brushing us off for so long; now we are playing catch up to discover and develop new treatment options and get them approved right at the point where current drugs don’t work. It is incredibly frustrating.