Changes

**Replicates in nasal epithelium -> throughout upper respiratory tract -> bronchial tree

**Replicates in nasal epithelium -> throughout upper respiratory tract -> bronchial tree

**Syncytia form -> shed into bronchioles

**Syncytia form -> shed into bronchioles

**Complications include [[Lungs - ventilation#Emphysema|emphysema]] and [[Lungs - circulatory#Pulmonary oedema|oedema]], drop in milk yield in adult cattle

**Complications include [[Lungs Ventilation - Pathology#Emphysema|emphysema]] and [[Lungs - circulatory#Pulmonary oedema|oedema]], drop in milk yield in adult cattle

*'''Epidemiology''':

*'''Epidemiology''':

**Subclinical reinfections are important in spreading disease

**Subclinical reinfections are important in spreading disease