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| Author |
Message |
    
R. W. Moreland (Moreland)
| | Posted on Saturday, Apr 7, 2001 - 11:30 pm: |   |
Has any one observed CNS signs in horses following worming with Quest? |
Robert N. Oglesby DVM (Dro)
| | Posted on Sunday, Apr 8, 2001 - 6:58 am: | |
I have not heard of any RW but two possible mechanisms might be:
1) killing of susceptible parsasites located in the CNS.
2) actual Moxidectin toxicity gives you CNS signs.
The first would most likely result in a focal assymetrical lesion with corresponding deficits the second results in generalized depression that can range from mild to unconsciesness.
Of course the most likely scenerio, if recommended doses are given, is coincidence.
DrO |
Ann Andersen
New Member
Username: Anniem
Post Number: 1
Registered: 9-2002
| | Posted on Thursday, Jan 9, 2003 - 10:51 pm: | |
Hi Dr.O, I used Quest for the first and last time just last week. Of the ten horses I wormed, one mare app.1200 plus lbs had a horrific reaction. The syringe treats up to 1150 lbs and I gave her a whole syringe, so she was not overdosed. Gave it at 4pm at 7pm noticed her lossing balance and motor skills. Called my vet immediately, he called it a neurological episode. She staggered and fell violenty many times causing much injury. This was an exceptionally healthy horse and has been given other wormers many times with no problems. The mare was far more than depressed, she came and went from and unconcious state for over 24 hrs. My vet has been documenting it for the Fort Dodge representative. I researched Quest and thought it was safe. Fort Dodge's own website denounces what they call "nasty internet rumors" as unsubstantiated. They are not rumors. My mare will live but probably have complications.
|
S. T. Bruce
Member
Username: Kari
Post Number: 159
Registered: 3-2000
| | Posted on Friday, Jan 10, 2003 - 12:19 am: | |
I have been using Quest for the past three years. On Jan.2nd. this year I wormed three broodmares, three wealings, and one donkey giving each a dose that was actually more than the recommended amount due to weight and had no adverse reaction. Ann's experience is terrible but I wonder if there are other causes that contributed to her problem. |
Robert N. Oglesby DVM
Moderator
Username: Dro
Post Number: 7562
Registered: 1-1997
| | Posted on Friday, Jan 10, 2003 - 6:19 am: | |
Hello Ann,
I am afaid there is no product, food, or situation in life that is 100% safe. Quest is safe for the vast majority of horses at up to 3 times the labeled dosage. I know I have given thousands of doses without a single reaction.
There are several possiblities in your case, one of which is the reaction is not related to the medication. Since many thousands of doses are given everyday around the world, there are going to be some serious diseases that are temporally asociated with the administration of the medication where there is no causal relationship.
That said, I think this is likely to be a reaction to Quest, because the timing and symptoms are what would be expected if an overdosage had ocurred. There was an interesting case last year where there was a herd reaction to ivermectin and it was thought that recent grazing on night shade may have greatly increased the toxicity. This is interesting because Quest is in the same class of drugs.
Take heart, in cases where death does not occur the animals do make a complete recovery. Keep us informed of your horses progress and developments.
DrO |
Emily French
Member
Username: Jcsmoon
Post Number: 631
Registered: 10-2002
| | Posted on Thursday, Jan 16, 2003 - 9:04 pm: | |
Dr O can you comment on the following: That the active ingredient in Quest is a fat stored toxin, thus allowing less frequency in worming. That due to this if the said horse is under weight (I realize the horse in question was not) that in the absence of acceptable body fat that the toxin can look to the mylin sheath and thereby cause neurolocigal complications?
Would appreciate any light you can shed as this has been my understanding of the product and have there for not used it on any underweight rescue horses. |
Robert N. Oglesby DVM
Moderator
Username: Dro
Post Number: 7611
Registered: 1-1997
| | Posted on Friday, Jan 17, 2003 - 7:48 am: | |
Not intelligently Emily. These are not well studied qustions and more complicated than they appear on the surface. For instance the location of the receptors may not be behind myelin sheaths, but perhaps in the nodes of Ranier or most likely, on the ends where they exert their toxic effect: increased GABA sensitivity and release. The decrease in fat may actually inhibit absorption of the avermectin into the the myelin sheath or the CSF, since it is a fat soluble molecule (cyclic macrolide). Are the critical neurons even sheathed in myelin? Most neurons found in the brain and spinal cord are not.
As I understand it, the best understood critical factor is the blood brain barrier that prevents high levels of the avermectin from entering the csf. There are no studies on how body condition effects these levels that I can find, though it would be useful. I can think of both positive and negative factors that a decrease in condition might have on absorption.
The closest I can find is a study in pigs of the effects of body condition on pharmokinetics of moxidectin. As would be suspected the thin animals had higher serum levels of moxidectin than the fat ones because there is less body fat to absorb it. However the concentration of drug in the fat tissues was the same in both groups. If the central nervous system behaves like fat, and for many folks it does, then condition should have no effect.
I do not avoid the use of Quest in thin animals, just those debilitated or have evidence of large worm burdens.
DrO |
