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Aspergillosis

Fungal Pneumonia, Mycosis

Aspergillosis Overview


Aspergillosis is a common, non-contagious fungal infection of ducks caused by members of the fungal genus Aspergillus. A. fumigatus is the most common species isolated from infected ducks. Aspergillus spp. are widespread in nature. Healthy ducks are regularly exposed to fungal spores on a daily basis, sometimes even carrying them in their lungs and air sacs without causing a problem. However, Aspergillus spp. are quite opportunistic, so if a vulnerable duck is exposed (usually the result of a concurrent infection or injury that has worn down their immune defenses), than it takes the opportunity to cause infection. Clinical signs vary widely, depending on what organs are affected. Aspergillosis can be either localized or diffuse, and often results in a progressive, debilitating illness. Aspergillosis usually affects the duck's upper and lower respiratory tract, although any organ systems can become infected.

Ducks are most susceptible to becoming infected with Aspergillus spp. during the following situations:
  • They have been receiving antibiotics and/or steroids for longer than a week in duration.
  • They are regularly exposed to damp bedding that is rarely changed
  • They are living in a warm, humid environment with poor air circulation or ventilation.
  • They are regularly exposed to large accumulations of dust; on the walls, bedding, and/or surrounding objects, especially at those surfaces that at their same level.
  • They have a concurrent or chronic disease, resulting in pain and/or impairment of the immune system.
  • They are living in overcrowded conditions
  • They are kept in a poor sanitary environment that is rarely cleaned, with a buildup of feces.
  • They are given moldy feed to eat, or exposed regularly to mold accumulation on old damp bedding, straw, hay, leftover food substances, etc.
Aspergillus spp. are opportunistic fungi commonly found in nature in the environment (bedding litter, hay, straw, dust, air), soil and feed grains. They are distributed worldwide and tend to multiply rapidly with high humidity and warm (> 77°F (25°C)) temperatures. Aspergillosis can manifest in both acute and chronic form.
  • Acute disease: Acute aspergillosis is a fatal respiratory disease that most commonly occurs in young, highly stressed or immunocompromised, newly captive ducks that are exposed to large amounts of Aspergillus spores in their captive environment. Clinical signs have a rapid onset, resulting in death in a matter of days. Most commonly observed signs include depression, difficulty breathing, lethargy, loss of appetite, increased thirst, cyanosis, abdominal enlargement, and sometimes sudden death.
  • Chronic aspergillosis: Chronic aspergillosis is usually the most frequent form of aspergillosis in ducks, and is most common in mature, adult ducks. These ducks usually have a recent history of receiving antibiotics or corticosteroids, previous disease, stressful event (relocation to a new location, predator attack, etc.), or suffering from a chronic disease such as bumblefoot. Clinical signs develop slowly, and often non-specific, such as reduced activity level, loss of appetite, change in behavior, or weight loss while maintaining a good appetite. When air sacculitis is involved, caused by infection of the air sacs with the fungus, clinical signs include increased respiratory effort, vocalization changes, tail-bobbing, open-mouthed breathing, and audible respiratory sounds.
Transmission
Aspergillosis is not a transmittable disease, ducks are infected through inhaling Aspergillus spores in the environment. Since multiple flock members live in the same environment, multiple birds may become affected.

Treatment
Aspergillosis treatment requires long-term antifungal therapy, often required for a minimum of 8 weeks.

Symptoms

Coughing
Lethargy
Loss of appetite
Open-mouthed breathing
Tail bobs
Wheezing
Voice change
Rapid weight loss
Convulsions
Paralysis

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Fungal culture
  • Radiographs of lungs
  • Necropsy -Presence of yellowish white nodular growths of various sizes in lungs, abdominal cavity and intercostals areas with thickened air sacs.
  • Histopathology - lungs display multiple foci of g

Treatment

Echinacea Purpurea Root Extract
Nekton T for Doves and other Domestic Fowl
Nekton-E Vitamin E Supplement
MethodMethod Summary
Itraconazole10 mg/kg PO BID for 4-6 weeks
Amphotericin B1.5 mg/kg administered IV-SC daily
Ketoconazole25 mg/kg administered orally, twice a day
Tarwood (Loxostylis alata) extract200 mg/kg

Prevention

  • Minimizing use of antibiotics and corticosteroids
  • Sporadic or repeated antifungal treatment by spraying fungistatic agents such as thiabendazole, nystatin, or copper sulphate on bedding litter
  • Maximizing ventilation
  • Provide balanced nutrients
  • Do not overcrowd
  • Eliminate moldy feed from the bird's diet and environment
  • Line areas exposed to slow drainage with a coarse material such as pea gravel.
  • Old food, decaying vegetable matter, and dried fecal matter should be regularly cleaned from the bird's pen
  • Frequently move feed troughs and water dispensers
  • Place feeders and waterers on elevated platforms
  • Conduct regular air quality tests

References

Risk Factors

  • Inadequate ventilation
  • Poor quality feed
  • Poor bedding litter quality, storage or management
  • Improper storage of feed
  • High humidity levels
  • Vitamin A deficiency
  • Stress
  • Repeated or prolonged use of antibiotics or steroids
  • Exposure to large number of spores
  • Concurrent illness or infection

Seasonality

WinterSpringSummerAutumn