I agree. Super bugs and the fast method of transmission from mega hatcheries, at poultry shows and close proximity to neighbors.
Many adults and children on the Oregon Trail died of Cholera, Typhus, Scarlet Fever, and who knows what else. Most of my ancestors ate or traded their chickens long before they got to Cheyenne or La Grande. When they settled in Washington and Oregon, they were on farms of average 150 acres or more. I'd call that bio security.
Yes, but you have to admit that - while your ancestors didn't make it all the way with their birds, some birds did make it the whole trek. And for those like your ancestors living on the large acre farms, they had to start over - presumably with birds from someone who made it the whole way. And then they probably supplemented with birds from someone else that made it the whole way, and on and on... My point being that they definitely had to be swapping birds. Maybe they didn't have access to large shows and/or swap meets like today, but there was swapping... Maybe they didn't live across a fence from a neighbor, but there was swapping... It doesn't matter if you live on 150 acres, if you go to town and being home new chickens from the market or if you go to the neighboring farms and bring home some birds - they were probably not actively practicing bio security as you all term it.
And I don't know about the argument that they were not subject to the contagious diseases we have today. If not the same diseases, then something else. I think it's naive to think only our current generation is fighting disease.
While I'm thinking about it, you all seem to have a much higher incidence of disease in your area (pacific northwest, yes?). Why do you think that you are having such a hard time with this ILT or whatever it is? I would typically guess it has something to do with your cooler, wetter climate - but you all say your having a heat wave now. I'm just curious because we don't seem to have such a prevalence here - at least not that I am aware of.