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Discussion on Acetylcholinesterace inhibitors
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Member:
Christos
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Posted on Wednesday, Jan 7, 2004 - 12:31 pm:
Dr O,
I have recently read that many pesticides, along with some dewormers, contain cholinesterace inhibitors that have a cumulating effect in the horse.
What substances are cholinesterace inhibitors?
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Moderator:
DrO
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Posted on Thursday, Jan 8, 2004 - 6:44 am:
None of the deworming products we recommend have cholinesterase inhibitors Christos and have no recognized cumulative effect.
Many types of insecticides do and these are classifed as organophosphates and carbamates. If you use insecticides as repellants we suggest you stay with the commonly available pyrethrins in all but the most dire circumstances: there are some places in the world where insect bites commonly transmit life threatening diseases. In such circumstances more potent help is justified.
DrO
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Member:
Christos
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Posted on Thursday, Jan 8, 2004 - 8:45 am:
I read this in the US Pony Club Manual, vol.C, in some general information about the nervous system. That's a credible, albeit general book, isn't it?
Thinking about possible cumulative effects, I read your article on Pyrantel, which is a common daily dewormer, and it does say that it is a cholinesterase inhibitor.
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Moderator:
DrO
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Posted on Friday, Jan 9, 2004 - 5:57 am:
Though this was thought to be true at one time this is no longer so. Pyrantel and the closely related morantel are agonists of nicotinic acetylcholine receptors of nematode muscle cells and causes a spastic paralysis (Vet J. 1997 Jul;154(1):11-34). This mechanism of action is different than antagonizing the release of (inhibiting) acetylcholine estrase. Experimentally on nematodes the effects look identical and is the reason for the earlier confusion. Thanks for bringing this to my attention Christos, I had not realized that this was uncorrected in the site and will do that, sorry for any confusion.
DrO
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Member:
Christos
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Posted on Friday, Jan 9, 2004 - 7:58 am:
Thank you very much for the clarification, doctor, I will amend that book as well.
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Moderator:
DrO
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Posted on Sunday, Jan 11, 2004 - 8:58 am:
One last comment about possible sources of exposure of horses to OP. The feed through fly control systems use Rabon, an organosphosphate. Recently it has been found that there is a bit more absorption of the product than thought previously. Though the product is still considered safe I recently heard the opinion that it should be discontinued in pregnant mares, a recommendation I have made for years.
DrO
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Member:
Christos
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Posted on Sunday, Jan 11, 2004 - 4:49 pm:
Thanks, Doctor,
I read today that as of Dec 2002 there's an official notice from EPA, stating the dangers of using tetrachlorvinphos, the active ingredient in most of these feed-through pesticides.
This notice also states that the labels of such products should clearly describe these dangers.
The link is:
https://my.execpc.com/~mjstouff/articles/horsefly.html#OPHOS
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Member:
Albionsh
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Posted on Sunday, Jan 11, 2004 - 7:18 pm:
This is scary. I have two mares expecting early summer foals, and they had access to the Rabon feed-through mineral blocks two periods this last summer/early fall. Is there anything I can do at this stage? A detox solution?
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Moderator:
DrO
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Posted on Monday, Jan 12, 2004 - 5:49 am:
Nancy,
I would try and not worry. The warning is hypothetical and not because of any established problem. You probaby are not at much increased risk of trouble.
DrO
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