I responded with a sad face and now I feel I have to explain it. It was not meant in a judgmental way, but to express sympathy that you had to deal with a sick bird in your flock and it had such an unfortunate outcome. Having read a few of these threads, it seems that sometimes a bird has an underlying issue that they successfully hide from their owners, but the parasites are not fooled and they take over. The rest of the flock, being in good health with good immune systems, are not attacked. That's just my opinion anyway.