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Aspergillosis

Other Names: Mycotic Infection, Bronchomycosis, Pneumomycosis, Pulmonary Aspergillosis

Aspergillosis is a noncontagious, opportunistic fungal (mycotic) infection caused by Aspergillus spores. The disease is common in chickens and other captive birds. Birds are particularly susceptible due to their unique respiratory system. A. fumigatus is the most common causative species, followed by A. flavus. Aspergillus spores are ubiquitous in the environment, and grow anywhere there is organic matter and moisture, especially in warm, humid weather.

Aspergillosis can occur in either an acute or chronic form:

Acute form (brooder pneumonia): Most often seen in young chicks after exposure to high concentrations of fungal spores.
Chronic form: Typically affects adult chickens, especially those with weakened immune systems.

In addition to these forms, aspergillosis can present in different ways depending on which organs are involved. The most common type in chickens is pulmonary aspergillosis, which affects the respiratory system. Less common forms may involve the eyes (ophthalmitis), brain (encephalitis), skin (dermatitis), joints (osteomycosis), or multiple organs (systemic infection).

Transmission

Chickens become infected by inhaling
Aspergillus spores from their environment. These spores are commonly found in dust, especially when moldy bedding, hay, or feed is disturbed.

In some cases, spores may remain dormant in the lungs or air sacs and only cause disease later, often triggered by stress, illness, or a weakened immune system.

Diagnosis

Early diagnosis can be challenging, as clinical signs often do not appear until the disease is advanced. A combination of tests is typically required, including blood work, fungal cultures, imaging, and tissue evaluation.

Blood work: May show elevated liver enzymes, increased uric acid, electrolyte imbalances, low albumin-to-globulin ratio, and high white blood cell counts. Repeated blood work can be used to evaluate disease progression and treatment success.
Radiographs: Can reveal cloudiness in the lungs or air sacs or granulomas once the disease has advanced.
Cytology and fungal culture: Samples from the respiratory tract may identify fungal structures.
Necropsy: Often reveals white or yellow plaques, nodules, or mold-like lesions in the lungs and air sacs.

Clinical Signs of Aspergillosis in Chickens

Signs vary depending on disease severity and organs affected but may include:

Difficulty breathing, rapid breathing, or tail bobbing.
Reduced appetite and weight loss.
Lethargy and depression.
Changes in vocalization or reduced crowing in roosters.
Increased thirst.
Nasal or eye discharge, cloudy eyes, or swelling around the eyes.
Neurological signs such as torticollis ("wry neck").
Green urates in droppings.

Treatment

Treatment is often difficult and prolonged, typically lasting several months. It involves antifungal medications, environmental management, and supportive care.

Environmental changes: Eliminate mold sources and improve air quality.
Antifungal medications: May include itraconazole, amphotericin B, voriconazole, fluconazole, ketoconazole, or terbinafine.
Topical or nebulized therapy: Antifungal agents may be applied directly or administered via nebulization.

Clinical Signs

Depression

Loss or change in voice pitch

Reduced crowing

Difficulty breathing

Tail bobbing

Increased thirst

Respiratory abnormalities (dyspnea, tachypnea, cyanosis)

Reduced appetite

Weight loss

Lethargy

Enlarged nares

Torticollis

Green urates in droppings

Cloudy cornea

Eye discharge

Blepharospasm

Diagnosis

History
Clinical signs
Physical exam
Complete blood count (CBC)
Fungal culture - taken of the throat, trachea or air sacs
Cytology
Endoscopy
Radiography
Necropsy and histopathology

Reported Cases

Case 1: Tracheal aspergillosis in a Chickens Tracheal aspergillosis was diagnosed in a flock of 3-week-old replacement pullets. The flock showed an increase in mortality after a windy weekend. At necropsy, the birds exhibited cyanotic beaks, small, yellowish, raised nodules on the tracheal mucosa (which was also hemorrhagic), and congested lungs, kidneys and liver. Microscopically there was brinonecrotic tracheitis associated with large numbers of septate fungal hyphae. Aspergillus fumigatus was isolated from several tracheas. Ref

Case 2: Tracheal aspergillosis in a Chickens Focal mycotic tracheitis resulting in obstruction of the syrinx was the cause of death in three chickens from three different premises with a history of unexplained, sudden death. Postmortem examination revealed a caseous plug formed from focal fungal infection obstructing the syrinx. Ref

Case 3: Disseminated aspergillosis in a Broiler breeders Increased morbidity and mortality occurred in a 5-wk-old broiler breeder replacement pullet flock. The affected broiler pullet flock was housed on the first floor of a two-story confinement building. Mortality increased to 0.1%/day compared to the flock on the second floor, which had mortality levels of less than 0.01%/day. Clinical signs in the affected chickens included inactivity, decreased response to stimuli, and anorexia. No respiratory or neurologic signs were observed. On necropsy, affected pullets were dehydrated and emaciated and had disseminated variably sized single or multiple heterophilic granulomas that contained intralesional septate and branching fungal hyphae. Lesions were extensive around the base of the heart in the thoracic inlet and in the kidneys. Other affected organs included eyelid, muscle, proventriculus, ventriculus, intestine, liver, spleen, lung, and heart. Aspergillus flavus was cultured from the visceral granulomas. The source of flock exposure to the organism was not determined. Ref

Case 4: Aspergillosis in a Chickens Two flocks of broiler chickens aged 15 to 30 days presented respiratory signs such as dyspnea and up to 25% mortality. These were the only two flocks in the farm where a bed of sunflower shells was used instead of the rice-hull bedding used in other flocks. At necropsy, severe ascites, right heart hypertrophy, pulmonary congestion, and extensive multifocal granulomatous pneumonia were recorded. Histopathologic examination revealed chronic multifocal mycotic granulomatous pneumonia. Aspergillus fumigatus was identified by microbiologic study from pulmonary specimens. After disinfecting the floor and changing the bedding, no clinical signs were recorded in the farm. Severe chronic granulomatous pneumonia caused by A. fumigatus in the chickens of the present study may have caused hypoxia, leading to pulmonary hypertension, heart failure, and ascites. Ref

Case 5: Aspergillosis in a Chickens Between the fifth and tenth day of life, 360 chicks from a flock of 4000 developed unspecific clinical signs and died. The birds were housed in a reused aviary litter, without previous treatment. In 11 six-day-old female ISA Brown chicks, necropsy revealed firm, yellowish-white, multinodular lesions extending from the pleura to the lung parenchyma. Histologically, a granulomatous, multifocal to coalescent pneumonia was observed. Granulomas were characterized by central necrosis, with heterophil and epithelioid macrophage infiltration and presence of countless Y-shaped intralesional septate hyphae morphologically compatible with Aspergillus spp. The diagnosis through isolation confirmed Aspergillus fumigatus. Ref

Case 6: Aspergillosis in a Kingfisher A 4-yr-old male Micronesian kingfisher was suspected of having an aspergillus infection. The infection was thought to be related to stress associated with movement to a new enclosure/exhibit and cage-mate aggression. The diagnosis was based on an elevated white cell count, positive antibody and antigen aspergillus titers, and abnormal plasma protein electrophoresis characterized by a moderate elevation of 2 and severe elevation on the protein fractions. The bird was treated with antifungal medication administered systemically and by nebulization for 10 wk. Response to treatment was monitored by serial white cell counts and plasma electrophoresis. Clinical improvement in this bird was correlated with a return of the white blood cell count to normal levels and what was considered a normal protein electrophoresis distribution. Ref

Case 7: Aspergillosis in a Pacific eider A four-year-old Pacific eider (sea duck) was reported to have a history of open-mouth breathing. They had been treated for suspected aspergillosis prior to death and was submitted to Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) for necropsy. At necropsy, the clinical suspicion of aspergillosis was confirmed. All air sacs were coated by green, velvety, fungal colonies that released spores upon manipulation. Some air sacs were also covered by thick layers of fibrin, and inflammatory exudate extended into the lungs. Histopathology showed abundant fungal hyphae coated by layers of conidia. Ref

Case 8: Aspergillosis in a Chickens Aspergillosis was diagnosed in two flocks of 9-day-old chicken broilers. The birds presented for gasping and elevated mortality. On necropsy, most birds had yellow, mucoid plugs partially occluding the trachea, in the region of the syrinx. Aspergillus favus, Aspergillus fumigatus and Zygomyces fungi were isolated from the lungs. The source of infection was most likely contaminated bedding material Ref

Case 9: Aspergillosis in a Hen A 5-month-old female chicken with a history of dyspnea was presented to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) in Gonzales for necropsy. Duration of illness was approximately one week. This bird was the only one that had died out of a flock of four. Upon examination, the bird weighed 692 grams and had moderate breast muscle atrophy. Numerous 1-3 mm, round, cream-colored nodules were present in the anterior and posterior air sacs and were scattered throughout the parenchyma of both lungs. The right primary bronchus, immediately distal to the syrinx, was completely occluded by caseous inflammatory exudate. Gross lesions consist of small, white, caseous nodules scattered throughout the lung tissue, usually accompanied by similar-sized caseous plaques on thickened air sac membranes. Caseous exudate can also be observed at the level of the syrinx and within the bronchi. Ref

Case 10: Aspergillosis in a Indian runner duck Aspergillosis was the cause of death of a 3-month-old, Indian runner duck, submitted with a clinical history of marked difficulty breathing. At necropsy, the bird had a localized accumulation of a yellowish exudate at the bifurcation of the trachea and syrinx, from which A. fumigatus was isolated. Histologically, severe inflammation and large numbers of fungal hyphae obstructed the tracheal lumen and infiltrated the cartilage rings. The litter material covered by a blackish mold in the coop of this bird was likely the source of infection. Ref

Case 11: Fungal ophthalmitis in a Chicks A flock of 15-day-old chicks from a breeder farm started developing unilateral periorbital swelling and turbid discharge from the eye, eyelids swollen shut and adhered together, with a cloudy cornea and cheesy yellow exudate within the conjunctival sac. Ref

Case 12: Mycotic keratitis in a Duck A 1.5-year-old female khaki Campbell duck was evaluated for lethargy and a swollen left eye (OS). Mucoid discharge, chemosis, and conjunctival hyperemia with trace aqueous flare, indicating anterior uveitis, in the anterior chamber were evident on ophthalmic examination. There was no fluorescein stain uptake by the cornea. Initial topical antibiotic therapy and systemic anti-inflammatory treatments were unsuccessful, and the lesion progressed to a diffuse, yellow-white plaque, which covered 90%–95% of the cornea 4 days later. There was moderate blepharospasm, mild blepharedema, and epiphora OS. The mobility of the nictitating membrane was impaired because of the presence of the plaque over the cornea. Cytologic examination of a corneal scraping revealed fungal hyphae, and aerobic culture confirmed Aspergillus species. Treatment with topical voriconazole (1 drop OS q4h–q6h) was initiated and was switched to oral voriconazole (20 mg/kg PO q12h) 6 days after initiating treatment. The ocular disease improved during the antifungal treatment period. Eighty-four days after initial presentation (9 days after discontinuation of treatment), there was no clinical evidence of mycotic keratitis on ophthalmic examination. Ref

Treatment

Name	Summary
Supportive care	Isolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Amphotericin B	J Huang 2018.
Clotrimazole	1% aqueous solution used for nasal flush or nebulization for 30-60 minutes. Can also be applied topically directly into the tracheal lesion.	J Huang 2018
Itraconazole	5-10 mg/kg administered orally, every 12 hours for 5 days, than once a day for 16 days. Usually given in combination with amphotericin B.	J Huang 2018
Ketoconazole	10-30 mg/kg bw administered orally, every 12 hours for 21 days.	J Huang 2018
Terbinafine hydrochloride	15-30 mg/kg administered orally, every 12 hours, in conjunction with itraconazole. Can also be nebulized as 1 mg/mL of aqueous solution for 20 minutes, every 8 hours.	J Huang 2018
Voriconazole	10 mg/kg every 12 hours, administered orally.	J Huang 2018
Fluconazole	5-15 mg/kg PO every 12 hours.	J Huang 2018

Support

Prevention

Minimize unnecessary antibiotic or corticosteroid use.
Maintain good ventilation in coops
Avoid damp, dusty, or moldy environments.
Regularly replace bedding, hay, and feed
Conduct regular air quality tests
Prevent standing water and excess moisture
Reduce exposure to respiratory irritants (e.g., fumes, sprays)

Prognosis

Treatment is usually long-term, frustrating, and often unrewarding if the disease is not recognized until the later stages of the infection. Early treatment is essential for a positive outcome.