Coccidiosis tends to be a disease of younger birds as they build up a resistance to it as they get older. Also it is more prevalent on wet ground, hence the high incidence of chicks dying if the bedding gets wet, For that reason also it is highly unlikely for adult birds to develop it when the weather has been so dry for so long. Finally - it is a disease which damages he gut, not the windpipe or lungs, so I would not suspect cocci in this instance.