I have pets in the trailer, so no poisons.
We have had really good luck with Fresh Cab, and then I made my own version of it in bulk, which I continue to spray on the original packets. Been rodent free since I started using it.
2015 24' Rockwood UltraLite 2304DS behind '14 Diesel Jeep Grand Cherokee/'04 Hemi Ram 1500. Equal-I-Zer 4-Point 1000lb sway control.