I feel bad for that bird, and for any pets that came into contact with it at the show. That just wouldn't go well at our events. We are very watchful. If a bird has parasites it is DQ. I watched every bird for signs when I was doing the bird watching one day. One had a droopy tail and I mentioned it, but she perked back up after some water (it was so hot).When I entered the barn all I saw were little girls in attendance. They each were holding a chicken and asked every single person if they wanted to pet it. I declined but most people were petting the chickens. I was appalled. That sick bird was so pale it was very obvious something was wrong in it's face. Judging hadn't started yet. I got out of that barn and washed my hands even though I never touched anything. And everything I had on went into the wash before I went back outside when I got home. I even wore a hat and my hair pulled back in a tight pony tail when I went in that barn. I have no idea how they get away with having no adults on duty. These were very little girls. Around nine or ten. There were maybe thirty chickens total in the cages.
Edited to add: I do remember seeing a group of adults outside the barn setting up a tent for showmanship. Noone was available to speak with. My resolve not to enter my birds in small fairs or shows like this stands.
You did the best thing when you got home.. wash everything.