I once had a rat problem at a different location and it was a lot of extra work each morning thoroughly cleaning the coop, scouring water and food containers etc. And worrying whether the rats might have a health impact on my feathered friends. (at first I wasn't sure what was getting in there, actually). For awhile I tried various repellents and hav-a-harts but eventually what worked the best was hardware cloth. I don't know how big your coop is but the one we decked out in hardware cloth was only about 4x6x8 foot high (2 birds) so the task was quite manageable. We put hardware cloth on the floor and wrapped it maybe 5 inches up the walls inside (the coop was maybe 5 inches off the ground). Stapled it down really well with those 'U" shaped staples so nobody would get their tootsies caught in any of the wire and then covered the floor with straw or pine shavings (depending upon time of year) and never saw a rat again. Their access points had been from below. Also just made sure there were no other holes where they could get in - there weren't but had their been, more hardware cloth would have been employed..............
I never have and never will use poison or anything that any other living being could get into and become an unintended victim.
I hope things are looking up there now...
JJ