You still have to deworm with ivermectin twice a year, as DWs don't get bots.
You should still do a tapeworm treatment at least once a year, preferably twice. You can combine the 2 and use Equimax twice a year.
There is growing information about more and more resistance of parasites to daily dewormers.
The last couple of years, and especially the last year, has been chock full of the vet-in-the-know community going to a "deworm as needed" recommendation because of more esistance of more parasites to more of the chemicals.
IMHO, there are very, very few horses who actually benefit from a DW. You are doing your horse, and the horse community in general, a huge service if you go with strategic deworming.
______________________________ The CoTH CYA - please consult w/your veterinarian under any and all circumstances. - ET
Some friends are in veterinary school, they convinced me to come off daily dewormer due to all the studies of resistance. I do a three way rotation 6x a year, depending on where you live, you can probably find a calendar with recommended wormers for your area.
Our farm had included daily DW in the board, and at the advice of the vet, has decided to stop it and go to fecal check/worm as needed due to resisitance, she just let us know this last week. I always stopped the ddw in the winter anyway.
Vets have been saying for YEARS that this tollerance buildup was coming. It's here now. My vet and alot of my friend's vets say you really should be doing a fecal and then targeting which kind of paste dewormer you use for what kind of worms they specifically have.
I guess the animal health drug companies won't be making as much money on paste dewormer in the future. I bet that when paste dewormer technology came availible, there was a push from them to get people to believe that they had to do the every 8 week rotation so they could sell more paste. I don't know, I wasn't around when this change in worming routine took place.
Do all of us a favor and stop using daily!!! There are no other effective drugs. We're all SOL when it stops working.