You can worm your flock with Flubenvet in the feed there in the UK. You also probably can find Panacur 10% horse paste 1/4 ml per pound for 5 consecutive days, and that can treat most all worms including gapeworm and capillary worms that might cause breathing issues. If you use Panacur for dogs, then we would need to know the strength to refigure dosage. Sorry about your chicken.