*On its own causes [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhinitis]]
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*Often part of multi-aetiology disease complex (e.g. [[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]), often followed by [[:Category:Pasteurella and Mannheimia species|''Pasteurella sp.'']] obscuring viral origin
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*Replicates in airway epithelial cells and results in an initial [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis -> bronchiolitis]] -> extension into [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|alveoli]], causing [[Lungs Inflammatory - Pathology#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]]
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*Early stages may show [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|intracytoplasmic inclusions]]
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*The resulting exudate is predominantly neutrophilic
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*Positive confirmation lies in a Fluorescent Antibody Test (FAT) to the specific virus on frozen sections of tissue