Update. April, the only surviving hen of four pullets exposed to active ALV as chicks, is now exhibiting symptoms.
She's approaching three years of age, and every single day of those years have been a miracle of resistance to the virus that killed her mates. However, her latest eggs have been strange in shape, more like torpedo shaped than egg shaped. Her latest egg wouldn't allow the lid to close on the egg carton, though normal inside.
In fact, I just tried to feed it to her soft cooked, but she only took a bite and then ignored it. She's lethargic with droopy eyes. I'm doubtful she has much longer.
Oh no. :c I'm sorry