There are a couple of tings that you can do to clean and disinfect the inside of trailers, and trucks. The first thing that you will want to do is ge the inside reasonably clean. Pressure washing it out should do fine. Then use a disinfectant type cleaner. I have used a product made by Clorox that seems to work pretty well. Using it and a pump up sprayer, coat the inside, roof and walls of the trailer and let it soak for about five minutes. You don't want it to dry though, because the Chlorine or Bleach will no work teh way it is supposed to. After the Clorox has soaked for at least five minutes, Spray it out with Hot water. That way, anything that the Cleaner did not get will be killed by the heat.
Scott