I have read all of the very helpful and informative threads about these #@ critters over the last couple of years. I have a TB gelding that I am totally convinced is suffering from them. We have been following the recommended deworming protocol with very good results. My question is: how soon in the season to start? In the past we have not done the double dosing until we have seen a sign of discomfort. (either excessive rubbing/itching or an obvious sore.) But I would like to know if we can get a jump start on the problem and hopefully nip it n the bud! I am in SE Iowa. Spring is just around the corner! No flies yet, but any day now! Day time temps could be upper 30’s to upper 50’s. Night time lows just above freezing or maybe just below!! Thanks for any help, or suggestions!
I’m in New England, and have already done the double dose of Equimax for my two horses. Not because of neck threadworms, but because it has been warm enough for the yucky’s to come out! I figure if ticks are out and about, so are the worms! If I think mine need to be done again, I will not hesitate to double dose again, especially for the new horse since I don’t know her deworming history.
Until your temperatures are reliably above 45*, strongyle eggs are not hatching. If they aren’t hatching, there is nothing infective for the horse to ingest. So, unless you have done a FEC and showed a mod-high number that would require deworming, the ivermectin was wasted.
As well, ivermectin kills dung beetles, which are most active in Spring.
If I think mine need to be done again, I will not hesitate to double dose again, especially for the new horse since I don’t know her deworming history.
No “if I think” 
It’s too late for a FEC now, but if you “think” someone needs something, do a FEC first.
There’s no need to double dose for any reason other than the NTWs. New horse, no deworming history, isn’t a good reason to double dose.
Ivermectin is on unstable ground already, with a shortened ERP (egg reappearance period) already cropping up, and a growing resistance with pinworms. It should not be given just because, there needs to be good reasons to use it.
We have to protect it, and moxidectin, by using them as little as possible, while still as much as necessary. And “necessary” is for bots for even clean-FEC horses.
