I just finished treating my birds with Safeguard for worms (3 doses, 3 days apart) and am still seeing live worms (I'm pretty sure tape worm) in some of the droppings. How long do I have to wait until I retreat with Valbazen? I also have 5 ducks that live with my hens. I haven't seen any worms in their droppings, but I treated all of the birds to be on the safe side. Does anyone know if the Valbazen is safe for ducks as well as chickens?