Has anyone had problems with Quest dewormer? If so, what??
Replace Quest with any other dewormer, and the answer is “yes”
That’s because every drug will cause a problem for some subset of animals/people it’s used on.
The typical issues - when there are issues, which is not common - are neurological.
Some horses have died after having Quest. None of the ones I know about ever had a necropsy to prove it was moxidectin that caused it. That doesn’t mean it wasn’t, but not proven, and it also doesn’t mean it’s inherently dangerous.
Ivermectin has caused (proven and unproven) the same issues, including death, also not common.
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No,I’ve been using Quest for years. No problem.
No problem with Quest for 10yrs+.
Then I got a Hackney Pony & vet advised to avoid moxidectin.
That was 10+yrs ago & now I have a mini as well.
Per current vet, I paste Spring & Fall.
Spring with ivermectin
Fall ivermectin & praziquantel
3 healthy horses
21yo pony
18yo horse
7yo mini
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No. I have also been using Quest Plus for years, in the spring.
A horse can have a reaction (or develop one) to anything. My alpha horse (RIP Duke) had a bad reaction to the rabies vaccine when he was in his early 20’s; it was his last one. . He was so drug sensitive the amount of Happy Juice needed to work on his teeth, “wouldn’t phase the whiskers on a Quarter Horse”, yet I de-wormed him with Quest every spring without issue.
I would be more inclined to blame a reaction on (A) worm overload or (B) the horse’s own immune system if the mouth were to blister.
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Ages ago, my vet advised me to use it for my gelding. I really was worried but she said he’d be fine, and he was. I’ve used it since (that was probably 99 or 2000) and haven’t had any issues. I never did use it for my pony or mini, but the horses have all been fine.
I have used it and never had an issue.
I used it for the first time last year (Quest Plus). 18 y.o Iberian WB. Other than her thinking I had poisoned her (she wouldn’t eat for like 2 hours), no problems. I had always been leary of it but I believe most of the issues have been in underweight, debilitated animals or animals where their weight was over estimated and they were then over dosed.
Susan
Yes. My horse became neurological after Quest. The first time I used it he was definitely “off” but it resolved within a day. The following year he was BAD. Awkward stance, odd gait, no interest in food. I called the vet and she said he is not a candidate for Quest anymore. She said it was because sometimes moxidectin is able to cross the blood-brain barrier. I do regular ivermectin in the spring and Equimax in the fall now and have no issues.
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The thing about Quest is that it kills some types of worms that ivermectin doesn’t. The first time I had a fecal done he was a heavy shedder. I use Equimax and Quest Plus in the spring and fall and usually one dose of ivermectin in the middle of the summer. We tested it and it took care of everything. Someone on this board - probably JB - will tell us which one you should use in the spring. I never remember. We moved to a new barn and I got a fecal in July. It came out down at the bottom. It was a huge change which I attribute to the lack of mud anywhere on the property.
Nothing in healthcare, including drugs and vaccines for people and horses and dogs and cats, is 100% effective. A longtime friend turned into a conspiracy theorist and antivaxxer. He started emailing me all sorts of weird articles, such as it is the Olympic, sister ship to Titanic, that is lying at the bottom of the Atlantic. I started sending him articles about vaccine use in horses. He couldn’t understand why. Because I have never seen or heard of an autistic horse.
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moxidectin kills encysted strongyles, which ivermectin doesn’t. And because of a fairly significant resistance with fenbendazole now, moxidectin is more effective than a Power Pack for those encysted stages.
In general, Quest Plus in Spring, Equimax in Fall, but there may be reasons to do it the other way around. Some feel that taking care of encysted stronglyes in the Fall is better, so they don’t sit in the horse over Winter. My take on that is I’d rather protect dung beetles than worry about what’s likely a pretty insignificant encysted colony. Ivermectin kills dung beetles, and they are most active in the Spring and into early Summer. Not so much in the Fall.
Is Quest Plus safe to use in a horse that has had EPM? I’ve heard conflicting ideas on that. I used Equimax last fall without problem on him, and have used QP on other (non-EPM) horses for years with no bad side effects.
I know quite a few EPM horses who get QP every Spring and are fine. That said, at least one of the owners does a round of Levamisole during that time, as an extra precaution.
I know a lot of people are afraid to use moxidectin on EPM horses, but have no problem using ivermectin, when both have the same potential to cross the blood-brain barrier, however tiny that potential is 
I would not use either one while the horse was actively recovering, just to be safe.
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I hope JB can answer this one…I just dewormed with Quest Plus (yeah, spring is springing already down here in Florida). We’re shipping our horses in about 40 days to the Midwest (moving). The boarding stable is requesting that they are wormed three days prior to getting up there in early April. Should I use Ivermectin? They will essentially be on dry lot between now and then.
This is an outdated practice, and is nicely addressed in the AAEP link https://aaep.org/sites/default/files/2021-03/Internal_Parasite_Guidelines.pdf
Go to page 3, Parasite Refugia
The concept of refugia can be utilized by keeping the frequency of drug treatments at a
minimum when pasture refugia is low (e.g., during the temperature extremes of cold winters or
hot summers and during droughts). Consequently, the old practice of “dose-and-move”, is now
considered to select more strongly for resistance, as moving newly dewormed horses to a new
pasture removes the dilution effect that would have been provided by a good size pasture
refugia (Waghorn et al., 2009
Quest will be good for at least 10 weeks, if not 12, so there won’t be any egg shedding before 10 weeks (and that’s assuming some resistance in the form of a shortened egg reappearance period (ERP). If you MUST use something, and they require some proof, I’d use ivermectin. But I wouldn’t use anything if you can get away with it. But that’s just me 
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Thanks, JB! 
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I’ve used Quest Plus with no issues. Typically use it in the spring and Equimax in the fall on my low shedders.
As others have said, some horses will have an issue with a certain drug. Same with people, dogs, cats. etc.
Can you even get it right now??
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Can you just take a picture of an empty tube of Dewormer 3 days out with your phone? Will have a date stamp on it - would that suffice vs worming again for no reason?
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A lot of big thoroughbred farms deworm horses before sales and shipping, and then they get to the new farm and have a positive fecal and the new manager freaks out. It’s largely pointless because the horses get stressed during shipping, which can lead to strongyles excysting and maturing. That’s our theory as parasitology researchers, at least.
Also, moxidectin isn’t going to get rid of all of the worms anyway. The stocking density and management practices are far more important for parasite control at the new farm than deworming horses prior to arrival.
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