Well that's a surprise - not. Rather unsettling though to put it mildly. Civilization learns nothing from history about the stress caused overcrowding or even just the simple proximity of people or animals and the resulting vulnerability to disease.
I am so fortunate to be able to buy meat and eggs from known free range/small scale or organic sources.
None of us are surprised, but in the name of cheap food anything goes.
Like you we are lucky to get meat from our neighbour. In fact lamb will be arriving next week