No, these will be the first in my flock that are vaccinated. There has been a nasty strain of mareks going around our area this past year and I have had three suspicious deaths from "coccidiosis" in older birds which weren't resolved with a coccidiocide which makes me think that they were actually mareks.is all of your flock vaccinated?
Did you know that the APA estimates that 70% of all chickens in the US will eventually die of mareks related illness. That is, it is so endemic and it is so detrimental to the immune system that they may die at 5yrs old of something like an upper respiratory illness but the fact is that the URI was really only allowed to take hold because mareks was depressing the birds immune system. Then there's the instance of mareks-related tumors which can pop up at any point in a birds life. Oy! Anyway, how long do you think it takes before the vaccine is fully effective?