Your contractual veterinary services company will outline a surveilance program for your flock. You do have veterinary guidance, right? So, you know that there will be microbiological sampling for Salmonella and Campylobacter early in the production cycle, again before they are moved or culled, and yet again once or twice before harvest. And, of course, if there is a positive test the birds will be destroyed. Also, the coop and run will be disinfected and tested again before restocking. Even commercial operations take those precautions and backyard chicken keepers are much more responsible.