*Usually secondary to viral infections such as [[Viral infections#Parainfluenza- 3|parainfluenza - 3]] or [[Viral infections#In Cattle|IBR]], bacterial infections such as ''Mycoplasma'' or environmental stress | *Usually secondary to viral infections such as [[Viral infections#Parainfluenza- 3|parainfluenza - 3]] or [[Viral infections#In Cattle|IBR]], bacterial infections such as ''Mycoplasma'' or environmental stress |