I have 9, 10 week old Silkies coming down with what I think is Mareks. The first one I found dead in the brooder. At first I thought she had just been suffocated by the other chicks in the "pile". I had turned off the heat lamp cause I thought they were old enough to keep warm by themselves. (they are in the basement brooder) Turned the lamp back on. Next day another one was down but not dead. I brought her upstairs and started giving water with a dropper. She got a little worse, then started getting better. Next day another one was down, but not as bad as the 2nd one. Brought her upstairs, same thing. this am, 3rd day, no one else down. This pm after work, another one down. I had read this thread this past week-end, and got some St John's Wort on the way home from work. I have dosed all 3 birds and will continue the treatment to see what happens. They are all pretty much back on their feet.
Will let you know what happens. I have a breeding pair of Crele Polish down there, and 2 male BL Polish. The Silkies were hatched by me, and have not been outside yet. none of these birds were vaccinated.
I also have, upstirs in a brooder, 9, 1 and 2 week old Crele Polish. I am giving them a diluted dose of St J in their drinking water. Can't hurt right?