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− | =='''Interstitial pneumonia'''== | + | =='''[[Interstitial Pneumonia]]'''== |
− | [[Image:Interstitial pneumonia micro.jpg|right|thumb|150px|<small><center>Interstitial pneumonia (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]] | |
− | *Lung inflammation that occurs primarily in '''alveolar walls''' rather than in alveolar spaces
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− | *Can be widely distributed but is often most severe in '''caudal lung lobes'''
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− | *Diffuse or patchy damage to alveolar septa, may be acute or chronic
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− | *Lesions in most cases result from '''blood-borne insult''' and are more likely to involve the '''dorsocaudal regions''', although the damage is often diffuse
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− | *No concentrated inflammatory response in the airway, only secondary to damage of alveolar walls
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− | *As part of systemic infection
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− | **[[Canine Distemper Virus|Canine distemper]] (in alveolar macrophages as inclusions)
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− | **Salmonellosis
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− | **Toxoplasmosis (in alveolar wall)
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− | *Acute interstitial pneumonia is characterised by '''exudation into the alveolar lumen''' and in cattle is associated with [[Pulmonary Emphysema|interstitial emphysema]]
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− | Examples:
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− | ====Acute bovine pulmonary emphysema and oedema (ABPEE)====
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− | [[Image:Fog fever 1.jpg|right|thumb|150px|<small><center>Fog fever (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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− | [[Image:Fog fever 2.jpg|right|thumb|150px|<small><center>Fog fever (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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− | [[Image:Tracheal haemorrhage in fog fever.jpg|right|thumb|150px|<small><center>Tracheal haemorrhages in fog fever (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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− | *Synonym: '''fog fever'''
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− | *Usually seen in adult beef cattle in the autumn as an outbreak
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− | *Associated with a change in pasture (from dry to lush, green)
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− | *Severe respiratory distress with laboured breathing and grunting on expiration
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− | *Can result in [[Diffuse Fibrosing Alveolitis|diffuse fibrosing alveolitis]]
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− | *Gross appearance is that of enlarged wet lungs, the interlobular septa are markedly widenedith [[Pulmonary Oedema|oedema]] and [[Pulmonary Emphysema|emphysema]]
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− | *Underlying pathogenesis is ingestion of L-tryptophan in the pasture which is metabolised to 3-methylindole -> bloodstream -> lungs -> metabolised into a compound toxic to Type 1 pneumonocytes and non-ciliated bronchiolar epithelium
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− | *Their loss allows massive flooding of the alveoli with a protein-rich fluid
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− | *The sequence of events in the lung is as follows:
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− | **Alveolar flooding with a protein-rich fluid due to the necrosis of Type 1 epithelium
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− | **As the incoming air dries this fluid, fibrinous 'hyaline membranes' form
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− | **Proliferation of the more resistant cuboidal Type 2 epithelium which line the alveoli, called 'epithelialisation'
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− | **Then either there is
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− | ***Digestion of the hyaline membranes by macrophages which when completed, allows some of the proliferated Type 2 epithelium to differentiate into Type 1 and reconstitute the functional respiratory unit - a normal alveolus
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− | **Or
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− | ***Organisation of the fibrin into fibrous tissue in the lumen - destroying the alveolus or proliferation of fibrous tissue in the alveolar wall with retention of the epithelialised appearance to the alveolus
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− | *Sequel
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− | **Residual scarring if animal survives initial onslaught
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− | **In chronic exposures there may be extensive fibroplasia
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− | *Ingestion of sweet potatoes ifested with ''Fusarium solani'' mould or pasture contaminated with stinkweed or purple mint, rapeseed and kale also cause pulmonary oedema, emphysema and interstitial pneumonia
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− | [[Image:Paraquat poisoning.jpg|right|thumb|150px|<small><center>Paraquat poisoning (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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− | ====Paraquat poisoning====
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− | *In dogs and cats
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− | *Free radical release causes damage to air-blood barrier
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− | *Depending on the dose, the lesions range from acute lesions (oedema, haemorrhage, hyaline membranes) -> chronic (fibroplasia of alveolar septae, replacement of alveolar cells with type II cells)
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− | *Additional extrapulmonary lesions to note following paraquat intoxication are '''necrosis of the adrenal zona glomerulosa and renal tubular epithelium'''
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− | ====Diffuse alveolitis====
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− | [[Image:Diffuse fibrosing alveolitis.jpg|right|thumb|150px|<small><center>Diffuse fibrosing alveolitis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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− | *Chronic disease of adult cattle occuring sporadically
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− | *Probably caused by repeated subclinical incidents of fog fever or farmer's lung
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− | *[[Extrinsic Allergic Bronchio-Alveolitis|'''Farmer's Lung''']]
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− | **Extrinsic allergic alveolitis
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− | **Hypersensitivity of ingested or inhaled moulds
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− | **May occur as an outbreak or sporadically in adult cattle
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− | *'''Hypersensitivity diseases''' often cause an lymphocytic interstitial pneumonia
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− | *Chronic interstitial pneumonia progresses to fibrosis
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− | **Sometimes called '''pneumonitis'''
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− | [[Category:Pneumonia]]
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