I'm gonna guess that the box Little A opened as a kid had some government-sent animal hormone inducing drug to improve animal product production and he maybe spilled way too much into the farm's water which his uncle, Fluffy, and the farm animals would've drunk and maybe it was ineffective on him cuz he was a kid? And then the first gen animals got taken away to be tested and their products that got sent out infected the human-turned, and the parents and uncle tried to cover up Little A's involvement...
I'm gonna guess that the box Little A opened as a kid had some government-sent animal hormone inducing drug to improve animal product production and he maybe spilled way too much into the farm's water which his uncle, Fluffy, and the farm animals would've drunk and maybe it was ineffective on him cuz he was a kid? And then the first gen animals got taken away to be tested and their products that got sent out infected the human-turned, and the parents and uncle tried to cover up Little A's involvement...