Zimectrin Gold is notorious for suddenly causing mouth ulcers in horses. It’s not the eradication of parasites. It’s the paste. Seems to be super caustic for a subset of horses. I never use it. Don’t want to tempt that result.
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Ouch, poor horse. 
That’s a significantly inflamed gumline on top of the ulcers. If it doesn’t resolve soon, I’d consider EOTRH.
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Isn’t that more at the gum line ? The erosion of a horses dentition ? Just asking.
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Not an abuser, just saying when you know better you do better. So don’t use it ever again. Equimax has more active ingredients and no risk for mouth ulcers so win win
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Yes, it can be. One of the early symptoms of EOTRH is an inflamed gum line before abscess tracts or resorption appear. It could be that whatever caused the ulcers caused what we see in the pictures, if it doesn’t go away but the ulcers do I’d want to take a closer look.
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More than a handful of people who have a problem, didn’t have a problem with their horse until they did
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Understood. Thank you !
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Any skin lesions? The mucosal appearance reminds me of cases of oral pemphigus that I have seen.
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ok small update - no deworming with zimecterin gold
horse is also not even in his teens yet so idk about EOTRH… my older mare has that and that wasn’t how it presented in her but obviously each horse is so different
also - what happens if you have to use zimecterin? (its the same as ivermectin, correct?) and sometimes you to have to use ivermectin (for example, in july, if horse is high wormer)
Not out of the question, but also pretty unlikely for EOTRH
The issue doesn’t exist with plain Zimecterin, just the Gold (and the Canadian Eqvalan Gold). There’s something about what they’ve done when they added praziquantel, but it’s NOT the prazi, as this really isn’t a thing with Equimax and Quest Plus.
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so it’s just the zimectin gold we just have to worry about?
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Pretty frequently discussed. Here is another thread.
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in the US yes. Eqvalan Gold is the same thing, with the same issue, in Canada
Where is this friend’s horse, OP? What region (general is ok). Is blister beetle out of the realm of possibility?
I know it is not your horse OP, but if it were mine I’d still want a dentist out to get to the bottom of what’s going on with the those teeth. It could be related to the mouth ulcers, it could be something else. Look at those photos up close. The incisor on the left caught my eye immediately with the abnormal wear on the enamel surface. Is that the tooth root poking out above the gum line?
Did this horse recently come from a bad situation? Did he ever eat of off a metal grate?
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we were talking about that as well (the condition of the tooth) - last night
especially that one on the far left, it looks super run down
the horse is only 11 years old, so it’s surprising to me that his teeth are in this shape, but then again i don’t really know what i’m looking at
both myself and owner aren’t thrilled with vet’s recommendation of “give him a few days off and readdress”
we are in virginia
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I wouldn’t be thrilled with that advice either. I’d want someone else to look at him.
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Since the possibility of using the nets came up, I would recommend sitting and just watching the horse use the nets for a while. Look at the pressure applied to the net by the horse, and the angle.
Kind of sounds like something else is happening here, but using the nets may be making things worse.
Can horses get lichen planus? I had it; this is what it looks like—white spider webby lesions in the mouth. Mine was assessed to be either a sign of an auto-immune disorder or caused by Advil. My provider said Advil is notorious for causing it and that the onset is sudden; one day, one Advil is too much and poof, you have lichen planus. It’s also potentially caused by other meds. I stopped taking Advil and it went away in about 4-6 months on its own.
https://www.mayoclinic.org/diseases-conditions/oral-lichen-planus/symptoms-causes/syc-20350869
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Thank you all for all of your advice and suggestions! For whatever reason his mouth has been healing! 
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