Paul's experience and observations are very interesting and trump anything I have to say.

One thing I have seen on occasion is a keeper gets a zonata that shows the symptoms and still keeps it the same way. In other words, the conditions were not changed to see what would happen. I completely understand when you have other zonata and do not want any possibility of the disease happening to the rest. But if a specimen can be isolated, or it is the only zonata in one's possession, a husbandry change should be initiated immediately.