Aspergillosis in Avian Wildlife

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Aspergillosis in Avian Wildlife

• Aggressive Diagnostics and Treatment
• Dont wait another day

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Avian Respiratory Anatomy

• Complete tracheal rings
• Prevents collapsing of trachea at high altitudes
• Strangulation during handling difficult
• Tracheal bifurcation cranial and dorsal to heart
  base
• Syrinx cranial to bifurcation
• Primary bronchus enters lung lobe, divides into
  secondary bronchus, then parabronchus
• Air flows from parabronchus to atria to air
  capillaries
• Oxygen and carbon dioxide exchange

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Air Sac Anatomy

• Four sets of air sacs
• Cervical
• Cranial thoracic
• Caudal thoracic
• Abdominal
• Varies with species
• Air sac membranes very thin
• No gas exchange in air sacs
• Very little vasculature to air sacs

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Avian Respiratory Physiology

• Every air capillary connected to adjoining air
  capillary
• Air flow is continuous and uni-directional
  (unlike mammals)
• Air cannot be trapped in lung therefore no
  pulmonary emphysema
• Lungs do not expand with inspiration
• Two breaths for air to circulate through
  respiratory system
• 1st inspiration- air shunted to caudal thoracic
  and abdominal air sacs
• Expiration- air moves from air sacs through lungs
• 2nd inspiration- air in lungs enters cranial
  thoracic and cervical air sacs

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Aspergillus spp.

• Ubiquitous, opportunistic fungus
• Thick walled, septate, branching
• Grows readily in moist, warm environments
• Found in soil, wood shavings, corn cob bedding,
  seed hulls, straw, etc.
• World-wide distribution
• Species
• Most common A. fumigatus, A. niger, A. flavus
• Less common A. glaucus, A. oryzae, A. nidulans

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Who is susceptible?

• Immuno-compromised animals
• Young, old, stressed (wildlife in captivity)
• Raptors
• Gyrfalcons, Goshawks, Bald eagles, Red-tailed
  hawks, Owls
• Most common cause of death in captive and
  recently captured free-ranging birds of prey
• Most important non-traumatic disease of birds of
  prey
• Aquatic birds
• Swans, geese, diving and shore birds
• Game birds
• Pheasants, wild turkeys
• Parrots
• African Greys, Pionus, BF amazons, mynah birds

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Some Susceptible Species
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Pathogenesis

• Forms- depend on chronicity, organs affected,
  number of spores exposed and host immune system
• Focal or localized lesions
• Trachea, bronchus, sinus, nasal cavity, skin
• Systemic infections- fungal hyphae are invasive,
  erode through body barriers and blood vessels
• Acute
• Chronic

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Acute Aspergillosis

• Overwhelming dose of fungal spores
• Clinical course over a few days
• Birds die in good body condition
• Invasive to pulmonary tissue with aerogenous and
  hematogenous dissemination
• Common site syrinx and tracheal bifurcation
• Turbulence of air forces spores drop out of air
  column
• Narrowing of trachea predisposes to blockage of
  necrotic debris

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Chronic Aspergillosis

• Low dose, granulation formation
• Slowly progressive, usually gt 3 weeks
• Exposure to low level of persistent spores
• Usually immuno-compromised individuals
• Recent imports, injured, migratory, long-term
  antibiotics therapy, inadequate nutrition,
  CAPTIVE WILDLIFE
• Respiratory disease usually extensive before
  clinical signs apparent
• Hypovitaminosis A gt squamous metaplasia gt spore
  invasion

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Clinical Signs

• Respiratory-
• Coughing, wheezing, change or loss in phonation,
  dyspnea, increased RR, open-mouth breathing,
  depression, emaciation, tail bobbing
• Gastro-Intestinal
• Biliverdinuria, diarrhea, regurgitation, anorexia
• Neurologic
• Posterior paresis, lameness
• /- ascites due to cardiogenic disease

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Focal Aspergillosis
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Diagnosis

• Non-specific
• Hematology
• WBC- heterophilia, monocytosis, lymphopenia
• RBC- non-regenerative anemia
• Serum chemistries
• SGOT (liver)- elevated
• CPK (muscle) elevated
• Hypoalbumenemia
• Hyperproteinemia and hypergammaglobulinemia
• Radiography

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Radiology

• Whole body
• Hyper-inflated air sacs, aerophagia, air in
  cloaca
• Focal densities in lungs or air sacs
• Thickened air sac walls
• Lateral view
• Syringeal or caudal thoracic air sac lesions
• Ventro-dorsal view
• Caudal thoracic and abdominal air sac lesions
• Head
• Nasal aspergillosis- turbinate destruction

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Other Non-specific Tests

• Serology
• Ag titers
• Ab titers
• PEP (protein electrophoresis)
• Separation of serum proteins utilizing an
  electric field and gel
• 5 protein fractions
• Increase in acute phase proteins (alpha 1 2,
  beta)
• Increase in chronic phase proteins (gamma
  globulins)
• Increase in total protein and globulins due to
  inflammation
• Can also be used to monitor response to treatment

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Definitive Diagnosis

• Cytological sampling
• Aspiration, lavage, endoscopy, celioscopy
• Wet mount with lactophenol cotton blue stain, new
  methylene blue
• Culture
• Endoscopic or swab
• Sabourand dextrose agar or blood agar
• Microscopic exam thick walled, septate hyphae
• Must see spores to speciate

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Treatment Goals

• General
• Prevention in captive animals is optimal
• Clean, sanitized, stress-free environ
• Well ventilated
• Prophylactic use of antifungals (?)
• Vaccine available for turkey poults for A.
  fumigatus (?)
• Dependence on location and extent of disease
• Aggressive therapy increases success
• Surgical debridement of airs sac or syringeal
  lesions
• Anti-fungal therapy

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Antifungal Therapy

• Goals of therapy (3)
• Lesions restricting air flow are removed (debulk)
• Kill or eliminate fungal organisms (antifungal
  meds)
• Support care during recovery (fluids, Ab, force
  feed)
• Amphotericin B
• Intra-tracheal
• Intra-venous
• Nebulization
• Oral anti-fungals
• Flucytosine
• Itraconazole
• Terbinafine (Lamisil)

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Amphotericin B

• Only fungicidal available and is gold standard
• Not absorbed orally
• IV or IO (initially) for severe cases
• Infused into air sac
• Intratracheally
• Nebulization

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Azoles

• Itraconazole
• For less severe cases
• Does NOT enter brain/CNS (Fluconazole does)
• Enhanced absorption with fatty meal

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Nebulization Therapy

• Drug Dosage (per 15 ml)
• Amikacin 75 mg
• Amphotericin B 100 mg
• Chloramphenicol 200 mg
• Enrofloxacin 150 mg
• Gentamicin 75 mg
• Tylosin 150 mg

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Nebulization

• Drugs amphotericin B or terbinafine (Lamasil)
• Allows penetration into air sacs
• Must micro-size droplet 3-5 microns diameter
• Can also administer through air sac cannula

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Zoonotic Potential

• Inhalation of spores
• Dose dependent
• Aspergillus must be sporulating
• Cutaneous contact
• Requires dermal integrity compromise (cuts, etc.)

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The End