There is a new wormer out i think its called melinbex or similar, it supposed to be very good, but it doesnt dissolve the worms, i used it aswell as Panacur with my recent litter. Maybe it was that ?
I only use Drontal Puppy with my litters, I found Panacur completely scoured them, gave them upset tummies for days! I've never seen worms in any of my dogs or pups, don't know if that means they've never had any or the Drontal dissolved them!