Hi Binka!

I don't think it's to the same degree as Collies, but Shelties are
also sensitive to Invermectin, so I wouldn't risk giving them
Heartguard. Oz is on Sentinel for heartworms. He could
also be on Interceptor too, but my vet doesn't carry that
one. Murph and Maddie's vet does, so that's what they're
on.

As to fleas, Sentinel also has flea preventative in it, so haven't
had to use anything else for fleas on Oz. When we went hiking
I did use Frontline to help with ticks, although it didn't do as
well as I would have liked or I should say it didn't do what I
expected. It's not a tick preventative, so ticks did get on Oz. It
kills them after they've attached. Frontline is also what I use for
Murph and Maddie, but I only use right before hiking with them
too.

I haven't heard the Collie folks mention steering clear of any
specific flea preventative. They are totally against the Pro Heart
shot and warn against Invermectin and also Immodium.

Par...