I'd say if you already have a diseased coop of birds yes in a healthy flock what would be in the poos esp after the bug ingest it and metabolizes it should be sterile the outside stuff is already in their surroundings. J/S
All the chicken meat sold at Wal-mart is from birds raised in houses where the poop is the litter they don't completely clean out those houses between flocks UNLESS there is a disease or contamination of some sort. They don't have a high mortality rate from this or they would soon fold under and be out of business and for sure if folks were getting sick from it they'd have to shut the doors too.
that makes sense. i guess i'm going to have to do some more research on the topic, before i get too many BSFL wandering into the chicken area.