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What are the four pathogen routes of entry into the lungs?
- Aerogenous (including aspiration)
- Direct entry
- Lymphatic spread
What are the four basic classifications of pneumonia?
Bronchopneumonia, interstitial pneumonia, granulomatous pneumonia, and embolic pneumonia
What are the four subclasses of bronchopneumonia?
Enzootic, suppurative, fibrinous and aspiration
Describe the pathogenesis of bronchopneumonia
Inhaled agents --> inflammation at the bronchoalveolar junction --> acute inflammatory response --> exudation of fluid and plasma proteins into bronchioles and alveoli --> recruitment of alveolar macrophages and emigration of neutrophils
What type of distribution does bronchopneumonia have?
What are the different causes of bronchopneumonia?
- Bacteria eg Pasteurella multocida, Mannheimia haemolytica, Bordatella bronchispeticaMycoplasmas
- Aspirated food/gut contents
- Viruses + secondary bacterial infection
What is the route of entry for bronchopneumonia?
What is the main cause of enzootic pneumonia?
What is another term for enzootic pneumonia?
Cuffing pneumonia, atypical pneumonia, chronic nonprogressive pneumonia
What can be seen on gross and histological appearance of enzootic pneumonia?
- Gross: cranioventral distribution, dark red, sharply demarcated, combination of collapse and consolidation
- Histology: peribronchial cuffing of lymphocytes and plasma cells
What is the main cause of suppurative pneumonia?
What is the main cell type found in suppurative pneumonia?
Neutrophils, typically degenerate
What is the distribution of suppurative pneumonia?
What substances are present in fibrinous pneumonia?
Fibrin, oedema, neutrophils (degenerate) and necrosis
What are the causes of fibrinous pneumonia?
- Mannheimia haemolytica (shipping fever), Histophilus somni - cattleActinobacillus pleuropneumoniae - pigs
- Aspiration of gut contents
What is the distribution of fibrinous pneumonia?
What can be seen on the gross surface of lungs with fibrinous pneumonia?
Fibrinous pleural surface and marked expansion of interlobular septae
What does Mannheimia haemolytica produce that causes tissue necrosis and fibrinous bronchopneumonia?
What is aspiration pneumonia?
When feed contents are found in the airways/alveoli in the middle of inflammation
What are the predisposing causes of aspiration pneumonia?
- Handfeeding neonatal animals
- Megaoesophagus from any cause
- Cleft palate/congenital abnormalities
- Down animals e.g. anaesthesia
- Iatrogenic e.g. putting feeding tube into lungs
What can be seen on gross inspection of aspiration pneumonia?
Often has a green/brown/black discolouration, perhaps foul smelling
What does BALT stand for?
Bronchial associated lymphoid tissue
What is the distribution of interstitial pneumonia?
What can be seen on gross inspection of lungs with interstitial pneumonia?
Large lungs that do not deflate, rib impressions, rubbery/meaty texture
What are the different causes of interstitial pneumonia?
- Viral (canine distemper, IBR, EVR, Maedi)
- Inhaled toxins/gases
- Toxic metabolites locally generated
- Acute respiratory distress syndrome (ARDS)
- Ventilator induced injury
What does PRRS stand for?
Porcine reproductive respiratory syndrome
What is the distribution of granulomatous pneumonia?
Multifocal, any lobe
What can be seen on histology with granulomatous pneumonia?
Macrophages plus multinucleate giant cells arranged as discrete granulomas or in sheets
What is the route of entry for granulomatous pneumonia?
Aerogenous, haematogenous or lymphatic spread
What are some possible causes of granulomatous pneumonia?
Fungal pneumonias, bacteria, parasites
Give an example of a parasite that can cause pneumonia
What type of parasite in sheep causes 'lead shot lesions'?
What is the distribution of embolic pneumonia?
What is the route of entry for embolic pneumonia?
What are the possible causes of embolic pneumonia?
Vegetative valvular endocarditis, hepatic abscesses, any septicaemia
What is the difference between primary and metastatic lung neoplasms?
Primary neoplasms originate in the lung whereas metastatic neoplasms have moved to the lung from another site (as the lung is a popular metastatic site due to its massive blood flow and capillary bed)
Primary lung neoplasms are commonly ... in origin?
What is the malignant/non-malignant form of epithelial neoplasms?
- Malignant - carcinoma
- Non-malignant - adenoma
What are the other cancer cell types?
Round cell and mesenchymal
What is feline 'lung-digit' syndrome?
This is when pulmonary carcinomas have a tendency to metastasise to multiple digits on multiple limbs. It is typically the first clinical sign in these cases.
What is the name of the virus that causes lung neoplasia in sheep? How does it do this?
Jaagsiekte or ovine pulmonary adenocarcinoma. This virus transforms alveolar epithelial cells (type II pneumocytes and clara cells) into a neoplastic population.
What test can be used to diagnose Jaagsiekte?
A wheelbarrow test - tip the sheep forward on its front legs and fluid will drip out of its nose
Give examples of areas where metastatic lung tumours come from
- Haemangiosarcoma (speen or right atrium)
- Mammary carcinomas