Hi, im really sorry about your hen, gape is a very distressing illness, both for the hen and the owner.Gape can be picked up from things like snails, grubs and worms, who are also hosts to the parasite. You cant stop your chickens from scratching and eating grubs....its chickens favorite activity! Periodically treat them with flubenvet. Its very simple to use, even simpler if you keep them in a run. At the start of treatment weigh 2kg of food, and mix 1 scoop (6g) of flubenvet into it, giving it a really good stir.Keep the medicated food in an air tight container, and only give them this food during the 7 days you need to worm them .Mix more food as needed, and offer it ad-lib like you would normally. If you want to give a very small amount of corn, only do so late in the day as you can be more sure that they have had plenty of medicated food. The larger hens generally eat more than the smaller ones, therefor getting the right amount for their weight. There is no egg withdrawel with flubenvet, so at least you can carry on eating the eggs. Some people recommed doubling the dose of wormer for gape also! It also may be worth looking at getting some disinfectant like stalosan F to sprinkle on the ground helping to keep things like worms under control. If your hen is no better tomorrow, take her to the vets as they can give an injection(ivemectin i think?) to get the flubenvet off to a good start!. Good luck with her and keep us informed.