Changes

*Some viruses are thought to induce modifications of the pulmonary defences by:

*Some viruses are thought to induce modifications of the pulmonary defences by:

**Damaging the upper respiratory tract, thereby facilitating bacterial attachment and colonisation, with reduced [[Respiratory System General Introduction - Pathology#Mucociliary escalator|mucociliary clearance]]

**Damaging the upper respiratory tract, thereby facilitating bacterial attachment and colonisation, with reduced [[Respiratory System General Introduction - Pathology#Mucociliary escalator|mucociliary clearance]]

**Decreasing surfactant levels by destroying Type 2 pneumonocytes

**Decreasing surfactant levels by destroying Type 2 pneu[[Monocytes - WikiBlood]]

**Impairing the phagocytic ability of alveolar macrophages

**Impairing the phagocytic ability of alveolar macrophages

*The pulmonary lesions develop very slowly hence this disease is uncommon in sheep < 2 years old

*The pulmonary lesions develop very slowly hence this disease is uncommon in sheep < 2 years old

*Increased respiratory rate upon exertion, loss of weight

*Increased respiratory rate upon exertion, loss of weight

*Remains in monocytes and macrophages

*Remains in [[Monocytes - WikiBlood]] and macrophages

*Gross findings

*Gross findings

**Severe [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]]

**Severe [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]]