“…7C and D , is caused by a virus t h a t is mainly s p r e a d by contact e x p o s u r e . The ability to infect chickens via the respiratory tract has been demonstrated by studies performed as early as the 1970s; infection through contact exposure with airborne suspensions of infective dander (1,9,15,31,32) and with infected individuals (34,39,48), administration of feather tip extracts (16,21), as well as cell-associated virus (38) were all shown to cause MD. However, some characteristics of these approaches, such as reproducibility issues, inability to deliver a quantifiable dose of virus, The effect of intratracheal infection on macrophages in the lung was assessed by immunohistology.…”