Keeping in mind that there are quite a few strains of leucosis, sometimes more than one being present in a flock, I am noticing less and less mortality from the virus over time. In the beginning, close to sixteen years ago, I was losing adult chickens frequently. There were a lot of individuals becoming paralyzed. Chicks hatched from the flock would die before age one year, and most embryos would not make it to term.
Now that all of my original chickens have died, and after I learned that hatching eggs from this flock was not advisable, I do not have a single symptomatic chicken from ages of eight months to eight years, two of which were hatched from my flock and all the rest originating from Privett Hatchery. It gives me hope that indeed this virus can become dormant in a flock after time, perhaps even recessive.