Really stupid question: how can one be sure their chickens do not have it? Can I treat them for it as if they do — so to be certain they aren’t carrying it in their digestive tract? Must I do a fecal smear — or should we just always assume that all our flocks carry it, and just wash our hands meticulously. (BTW, I already do — but my 80 year old mother, I am sure, isn’t as careful as she should be.)