# Quest dewormer and neurological issues



## 4horses (Nov 26, 2012)

Has anyone heard of Quest causing neurological issues?

There are a few videos on Facebook. 

I don't use Quest, but it is concerning if the dewormer is killing horses. I know dogs can be sensitive to ivermectin, has that been documented in horses?

According to this some horses can be sensitive to ivermectin.
http://avmajournals.avma.org/doi/abs/10.2460/javma.235.5.558?journalCode=javma


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## SlideStop (Dec 28, 2011)

When you worm a horse your giving it a neurotoxin, coincidentally this is a side effect of the medication. Quest is a new wormer on the market and the drugs in it, while strong, aren't "tried and true". Ivermectin, on the other hand, is so over used its creating "super bugs" because people think it's a "safe". 

I look at it like this, the majority of the population could eat a peanut butter sandwich every single day for the rest of their lives and the perfectly fine. Then there are a select few that are too sensitive to peanuts. Does it make peanuts bad for everyone? No! Should it be pulled off the shelves? No! But if you've never had contact with a peanut in your whole life you should exercise caution because there is a potential for an adverse reaction. This horse was likely super sensitive to this drug, just like my horse being a "light weight" or a "cheap date" when they have to tranquilize her. 

Another thing, I wormed my horse with quest plus this year and will probably worm with quest again in the spring. This video, while scary, doesn't deter me from using the product. It does, however, remind me that you should be dosing a horse appropriately and keeping a close eye on your animals administering any medications.
_Posted via Mobile Device_


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## PaintHorseMares (Apr 19, 2008)

We've used Quest for years without problems.
_Posted via Mobile Device_


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## Corporal (Jul 29, 2010)

Abstract
Journal of the American Veterinary Medical Association
September 1, *2009*,

Treatment and Outcome—All horses were treated supportively with IV administration of fluids and anti-inflammatory medications. Two horses survived with no apparent long-term sequelae. One horse was euthanized, and* a high concentration of ivermectin was detected in its brain tissue* at postmortem examination. Analysis of the ivermectin concentration in the paste product revealed that the concentration was approximately that indicated on the packaging.

Clinical Relevance—Ivermectin toxicosis is an uncommonly reported condition in equids that should be considered when acute neurologic impairment develops after ivermectin administration. Recovery is possible with supportive care and time.

_First,_ this was published 6 years ago. Had the drug become a problem, it would have been pulled from the market by now.
_Second,_ although the article is a documented clinical report, we don't know all of the details. Every horse owner treats with over the counter products differently. I do not deworm my horses through the winter, for instance. SOME people deworm on a schedule and are fastidious about deworming on time.
_Third,_ MANY people, overuse products with the "more is better" attitude. _(I use floor cleaning products in this way.)_ If you were to consume and digest too much of any drug, you can have problems with it. I used to take 4 ibuprofin at a time, and finally, my body had an allergic reaction to it and I can no longer take any ibuprofin without the reaction. The drug has to go somewhere in the body if you take too much, and I suspect it went to this horse's brain. 
We DON'T KNOW how often, or how much ivermecterin the euthanized horse was given by the owner prior to this incident. If you read the ingredients you will see that 1.87% (just shy of 2%) of ~1/4 cup of paste is the actual drug in the paste. *That is a tiny amount of a powerful drug,* even for an animal that big. Ivermectin is now used for human heart patients, and the amounts are very tiny.

I have dosed with ivermecterin for 30 years without any incident, except for horses trying to spit it out. =b
Regarding Quest, it is irritating that we have to now *deworm for tapeworms.* This has come about since I first owned horses and I never had to deworm for it 30 years ago. Most of this is from sloppy horse owners who keep their horses in filth and spread tapeworms. I dose my horses every year with praziquantel, now--I buy the least expensive dewormers with it--even in years when my horses do not travel. When we do travel, we often share paddocks used by other horses and not ever stripped and cleaned like we do at home. THIS, if nothing else, makes using dewormers a necessity.
People used to grow tobacco and feed a big leaf to deworm their horses. A horse with a large load of bloodworms will probably die from the bloodworms without treatment. Good feeding, meticulous cleanup of turnout/stalls, and general good health won't prevent a parasite load, but it helps keep it lower. We have recently discovered that some horses shed more worm eggs regularly than others, and some horses can resist a high parasite load, while other horses are more vulnerable to a high parasite load.
It is possible that the owner of the euthanized horse didn't keep the turnout areas clean, or shared the areas with others who didn't do so. Is is possible that the horse had just been acquired, in poor health, and the owner overdosed. If you suspect a very high parasite load, your Vet can administer a series of deworming doses that will eliminate the parasite load slowly, so that the parasite don't die off and clog arteries of the horse. I am no Vet and no Vet Tech, but a compromised animal is likely IMO to be the animal in this abstract that was euthanized.
You asked what we thought!
Btw, praziquantel was developed here, at the University of Illinois Vet School, as well as dry, pelleted dog food, (Animal Sciences), and I know the inventor of the latter.


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