It's one here, one there. It is not contagious. It tends to be more common in the heavy laying breeds, production reds being one of those. My production reds have had the highest amount of reproductive problems over all, compared to my other breeds. I actually avoid getting them now, they...
Definitely lash material. It's caused by salpingitis, which is inflammation or infection of the oviduct. Some birds may pass some of it, giving a clue, in others it just builds up inside. They are very, very good at hiding the symptoms and it's often not noticed until it's very advanced...