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Respiratory Fungal Infections - Pathology (view source)
Revision as of 16:23, 31 July 2008
, 16:23, 31 July 2008no edit summary
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===''Aspergillus fumigatus''===
[[Image:Aspergillus pneumonia of cattle.jpg|right|thumb|100px|<small><center>Aspergillus hyphae in cattle lung (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:Aspergillosis in nasal cavity.jpg|right|thumb|100px|<small><center>Nasal aspergillosis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*[[Aspergillus spp.|''Aspergillus fumigatus'']]
*Most commonly in dogs but also other species
*Causes [[Nasal cavity - inflammatory#Infectious causes of rhinitis|rhinitis]], often also involves the [[Paranasal sinuses - inflammatory#Infectious causes of sinusitis|frontal sinus]]
*Chronic necrotising inflammation with friable exudate containing necrotic tissue and fungal hyphae
* Result in severe neutrophilic [[Nasal cavity - inflammatory|rhinitis]]/[[Paranasal sinuses - inflammatory|sinusitis]]
*These lesions can be aggressive causing destruction of turbinates and nasal septum
*Can occur secondary to areas of mucosal compromise eg: adjacent to a space-occupying lesion
*Can cause pulmonary aspergillosis especially in '''birds''', but also other animals
**Initiated by inhalation of spores,the most likely source of which is mouldy feed and bedding
**Given the wide exposure that occurs, it is thought that immunodeficiency may contribute to colonisation with this organism
**Gross lesions :
***Multiple discrete grey/ white nodules which develop around fungal colonies
***Blood vessels can become involved in the lesions -> invasion, haemorrhage or thrombosis
**Histologically:
***Granulomatous chronic lesions
***Macrophages and epithelioid cells
***Fibrous capsule
*In horses:
**[[Nasal cavity - inflammatory#Infectious causes of rhinitis|Nasal aspergillosis]]
**[[Guttural pouches - inflammatory|Guttural pouch infections]] in horses - fungal plaques form on the adventitia of the carotid arteries can lead to catastrophic haemorrhage following erosion of carotid arteries!
**Often present with [[Respiratory System Clinical Signs - Pathology#Epistaxis|epistaxis]]
**May present with neurological dysfunction
**Rarely extends to other resions: cranium, middle ear, atlanto-occipital joint
**May extend to [[Paranasal sinuses - inflammatory#Infectious causes of sinusitis|sinuses]]
===''Cryptococcus neoformans''===
*[[Yeast-like fungi|''Cryptococcus neoformans'']]
*Causes a [[Nasal cavity - inflammatory#Infectious causes of rhinitis|granulomatous rhinitis]], gelatinous exudate, [[Lungs - inflammatory#Granulomatous pneumonia|granulomatous pneumonia]]
*Nodules or destructive masses which often result in facial swelling
*In severe cases, extension from nasal cavity to involve skin and oral mucosa can occur
*Can invade through adjacent structures, eg: through the cribiform plate into the brain! These cases therefore can present as a primary neurological disease.
*Microscopic:
**Large number of fungi and only few macrophages, lymphocytes and giant cells
===Blastomycosis===
*Caused by [[Yeast-like fungi|''Blastomyces dermatitidis'']]
*Occurs mainly in the Americas, Middle East and Africa, occasionally in Europe
*Mainly in young dogs, occasionally other species
*Can involve almost any tissue after spread from lungs
*Gross lesions:
**[[Lungs - inflammatory#Granulomatous pneumonia|Granulomatous pneumonia]]
*Microscopic lesions:
**Yeast fungi with thich walls in nodules with macrophages, neutrophils and giant cells
===Histoplasmosis===
*Caused by [[Yeast-like fungi|''Histoplasma capsulatum'']]
*Gross lesions in lungs:
**Firm encapsulated granulomas ([[Lungs - inflammatory#Granulomatous pneumonia|granulomatous pneumonia]])
*Microscopic lesions:
**Macrophages with inracytoplasmic yeasts
*Also in other tissues
===[[Fungi|''Pneumocystis carinii'']]===
*Important cause of pneumonia in humans associated with immunodeficiency states
*It has been occasionally reported in young or immunosuppressed animals (e.g. Arabian foals with congenital immunodeficiency)
*Grossly:
**Diffuse [[Lungs - inflammatory#Interstitial pneumonia|interstitial]] [[Lungs - inflammatory#Infectious causes of pneumonia|pneumonia]]
**Patches of firmness or consolidation
*Histologically:
**Alveoli are filled with pale staining acidophilic material (= trophozoite and cyst forms of the organism)
*It is thought that as P. carinii is often present as a latent infection, alveolar macrophages normally control the organism - a process which fails in immunodeficient states