Oh forgot, safeguard liquid, for goats, wormer...3 ml per gallon of water, for 2 days, repeat in 10 days. I would suggest repeating 3-4 times if necessary at ten day increments. That is, if you really think this is the gapes. Hope you get to the bottom of this! The point of retreating is to kill the eggs...the eggs don't even stay in fowl, just the worms and come from infested earthworms...maybe some other pests now, but earthworms were the primary vector.
In colder climates, if you treat a run with salt, according to the directions on the link, by spring, no more gapes! If you free range and have a gapes problem area, well, you might just have to treat on a regular basis, when you see the gapes starting up. That is, if you really think this is what it is. Nasty little buggers if you ask me...yuckkkk!!!