As much as we vaccinate and treat them for the other nasties, along with garlic etc in the drinkers. I think all new birds should be quarantined no matter who gives you them or where you get them from, saying that we have gave away over 200 birds (including Billy's) this year and never had a bad report, but we never take the chance even birds from Ferry were quarantined knowing how good he looks after his stock :-/
Just the way Chickadee does it