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