query re horse manure bad if horse were dewormed?

I have a big garbage can of manure with sawdust I got from a riding stable in a nearby town. I was just told that I needed to know if the horses were treated with a deworming agent because if so, the manure would kill the worms in my soil.
Is this true? I don't know much about horses or worms--wouldn't all riding stables give their horses something to deworm them? Thanks!

Great question...have you googled it since no one seems to come forward?

How fun to have a reply from Hawaii. Thanks for the nudge. It looks as if I'm fine to use my manure. I found this on a Co. Extension Division site. It's about vermiculture so answer relates to red worms, but close enough for me:
Will horse dewormers kill red worms?
The most common wormer used is known by the brand name Ivermectin® made by the Merial
Company. Merial’s research shows that the active chemicals in Ivermectin® are deactivated when
manure is exposed to sunlight. Equine studies show that 95 percent of the active chemicals in
Ivermectin® are deactivated in the horse before being passed in the feces. Leading experts in
vermicomposting believe that the concentration of Ivermectin® in the horse manure is not high
enough to seriously injure Eisenia.

Great news....thanks for that!!!!