In the past month, I have lost three 7- and 8-month-old Belgian D'Anvers cockerels -- two of them within a couple weeks of each other. They were part of a flock of bantam chickens of several breeds. So far, only these D'Anvers birds have sickened and died. They got sick one at a time, not all at once, with at least a couple of weeks between birds. They're hatchery birds I got as day old chicks and have raised them. They were introduced to the old flock in the late summer and there were no problems until around a month ago when the first bird got sick. I'm thinking that this bunch of D'Anvers may not have the genetic resistance to disease and are more susceptible than the other birds. I have two D'Anvers left, a cockerel and a pullet, so I'm worried about their wellbeing. All of the flock live in a 12X20' barn with a run. I clean it twice a day every day, The symptoms start with a noticeable decrease in vigor -- birds that were very active start slowing down. Then they become depressed, going off to a dark corner alone. Then, breathing becomes labored. No coughing or discharges, just labored breathing. Shortly before death there is a little gurgling, but no rattling or rasping. The time from onset of the noticeable symptoms to death (and it has been fatal for all three cockerels) is 5-7 days. Those are the only symptoms. Until hours before death, the birds ate and drank normally and there was no loss of appetite. As soon as I noticed the symptoms, I quarantined the birds. My guess about their gasping is fluid in the lungs, but I have not done a post-mortem because I don't have the facilities to do it, and I didn't want to leave the carcasses around after death. I think it's a virus, and probably there is no treatment, but it would be good to know what it is, if anyone has an idea.