I have a friend who worked for a local ag dealership that sold New Holland skid steers . We have a large number of chicken houses in the county. Several farms have over 1 million chickens for egg production.Some others raise and finish turkeys.They sell the chicken manure at a auction 1 time a year and it brings in buyers from several states. So far everything is normal except my friend is loosing his eye sight from some thing caused by the chicken manure. He was exposed to it daily from working on the machines at the dealership, and on service calls at the various farms. Plasmoseis Is what the stuff is called,I believe. The dealer has a brother who has hired my friend to milk cows since he can can not pass his vision test to drive the repair truck.