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Aspergillosis |
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- Ubiquitous fungi, primary pathogen in birds, opportunist in other species.
- Usually A. fumigatus, sometimes A. flavus, A. terreus, or A. niger
- Can cause localized or systemic infection
- Important producers of mycotoxins (i.e.. aflatoxins of A. flavus).
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Avian Aspergillosis |
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- Can occur in poultry, cage birds, exotics
"Brooder pneumonia" - young birds
Acute disease
+ Follows inhalation or ingestion of spores
+ Widely disseminated in body, death in 24-48 hr
Chronic infection
- older birds
Source- moldy feed, poor sanitation
Treatment
- intraconazole, others ineffective
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Aspergillosis |
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Cattle
- Abortion - in U.S. 5% of abortions are fungal
- Spores ingested or inhaled, disseminate to placenta
Sheep, horses
- similar to cattle
Dogs, cats
- respirattory infection
Reptiles
- respiratory infection
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Human Aspergillosis |
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-Better studied than animal disease
- Can colonize mucosal surface - fungal ball
- Invasion of lung - follows inhalation of many spores, or immunosuppression
- Disseminated infection - brain, kidney, CNS
- Allergic response- Spores in environment, or colonizing infection
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Aspergillosis - Pathogenesis |
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- Virulence mechanisms - elastase, proteases, cell wall products, toxins?
Spores inhaled
- Rely on Alv Mac to inactivate these
If spores germinate into hyphae
- Rely on PMNs to attack hyphae
If Alv Mac or PMNs defective
- fungal growth and tissue invasion results
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Aspergillosis - Therapy |
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- Resistant to most drugs
- Itraconazole appears most effective
- Eliminate source of spores (moldy feed)
- Remove fungal mass if possible
- Treatment failures common
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Aspergillosis - Diagnosis |
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- Microscopic examination of tracheal wash
- Histopathology - use fungal stain (silver), see dichotomous branching hyphae
- Culture - grows readily, but inhibited by cycloheximide
- Colonies in 48 hr, identify by spores
- Serology - tests available, can be false + or -
- Detect fungal Ag - suspected deep infection
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