If any new member has Mareks ,you won’t know in 30 days,unless they have blindness Or something obvious.
If newly vaccinated mereks,you can’t visit both groups,no one can, without spreading to the 2 week quarentine.Same house very hard.Friend house better,you can’t go visit.
The more you add separately ,the higher chance you’ll get,.never pet the chicks in store,then go home either.I peek though.
Pullets are even worse,because you have to trust they quarantined properly after vaccine.
Yes,I’ve had Mareks from careless breeder,Chicken scratch,in Illinois.
4 died same age heart Mareks,.
Others had leg paralysis,and one pullet came blind.2 others are just ok.Out of 8 1 is ok.Bought different time.Didn’t know Mareks until later.
They all lay eggs,the one with the weak legs recovered 3 weeks,you have help eat,give sugar water,,then it goes dormant.
lots of anti inflammatorys.( mobic)This keeps tumors from growing.The remaining 3 out of 4 get it everyday..They lay eggs act normal.
My properly vaccine and quarantined 6 hens,from Cackle,have never got it.They we’re the originals.
Getting new chicks are fun,do your homework,Listen to your vet,how to do safely.if they get it,no you don’t have to kill them,the others already would have been exposed anyway.
Though,my old and new are different coops.Play same area .This matters,a little.
integration best done with divider fence few weeks.