Fungal infections are a common health issue affecting birds. Just like humans and other animals, birds can suffer from various types of fungal infections throughout their lives. Some fungal infections are more prevalent and pose a greater health risk than others in avian species. Identifying the most widespread fungal infections in birds is important for bird owners and avian veterinarians to monitor bird health and quickly address any fungal disease issues.
Aspergillosis
One of the most common fungal infections seen in pet birds, wild birds, and poultry is aspergillosis. Aspergillosis is caused by infection with Aspergillus fungus, most often Aspergillus fumigatus. Spores from these molds and fungi are often found in the environment, in soil, decomposition, and organic debris. Birds inhale the spores which then can germinate in the lungs and air sacs leading to respiratory illness. Aspergillosis can also locally invade the trachea, sinuses, skin, brain, and other organs if the spores enter wounds or other openings. The disease poses a major threat to various avian species:
- Pets – Aspergillosis is frequently reported in pet budgerigars, cockatiels, parakeets, and other caged birds. Stress and poor ventilation that allows buildup of spores can increase risk.
- Poultry – Commercial turkeys, chickens, ducks, and other poultry are commonly affected by airborne Aspergillus spores which lead to losses from chronic respiratory disease.
- Wild Birds – Aspergillosis has been studied in a wide range of wild bird populations. Severe outbreaks occasionally occur in colonies of birds such as penguins.
- Captive Birds – Aquarium birds, zoo birds, rehabilitation birds, and other captive species are also susceptible in confined spaces.
Symptoms of avian aspergillosis may include labored breathing, sneezing, coughing, discharge from the eyes or nares, poor appetite, lethargy, and potentially death. Diagnosis involves radiographs, CT scans, endoscopy, biopsy, serology, and culture. Treatment depends on the severity and may include antifungal drugs, improved ventilation, and surgery to open blocked airways. Preventing exposure is key for population health through measures like controlling dust and aerosolization of organic matter where birds are housed.
Candidiasis
Candidiasis is another very prevalent fungal disease in birds caused by excessive growth of yeasts in the genus Candida. This fungal infection is found worldwide in wild birds, pet birds, commercial poultry flocks, and captive species. Some major features of avian candidiasis include:
- Crop Infection – Candidiasis often affects the crop first, leading to thick plaques, necrosis, and impaction.
- Gastrointestinal – From the crop, the infection can spread down to the proventriculus and ventriculus leading to systemic illness.
- Immunosuppression – Birds that are stressed or have compromised immune systems are most susceptible.
- Treatment – Topical antifungal medications, adding lactobacillus probiotics, fluid therapy, and removing predisposing factors.
Candidiasis frequently presents as a case of sour crop in pet birds that have a diet imbalance, are on antibiotics, or have diabetes. The crop becomes enlarged, slimy, and filled with food and yeast. Birds may show signs of weight loss, weakness, lethargy, and trouble swallowing or regurgitation. A bird’s breath may also have a foul odor. Diagnosis relies on crop swabs, cultures, and biopsies. Addressing the underlying condition and using antifungal drugs helps resolve the infection.
Cryptococcosis
Cryptococcosis is a fungal disease found globally in wild and captive birds caused by Cryptococcus neoformans and C. gattii. Most birds become infected through inhalation of fungal spores in the environment. Cryptococcosis can cause respiratory illness, but more often spreads to the central nervous system leading to life-threatening neurologic symptoms. Common signs in birds with cryptococcosis include:
- Nasal discharge
- Ocular discharge
- Depression
- Incoordination
- Weakness
- Paralysis
- Circling
- Head tilt
The fungal infection has been diagnosed in various avian groups:
- Pet Birds – Well-documented in cockatoos, macaws, amazons, budgerigars, lovebirds
- Raptors – Common in falcons used for hunting
- Wild Birds – Reported in species such as blue jays, California quail, wild turkeys
- Poultry – Seen occasionally in chickens, turkeys, ducks, geese
Diagnostic tests like cultures, serology, PCR, histopathology, and imaging can confirm cryptococcosis. Long-term antifungal treatment for months may be needed to resolve infections. This fungus has zoonotic potential and can also infect mammalian species, including people.
Conclusion
Aspergillosis, candidiasis, and cryptococcosis are three of the most prevalent fungal infections diagnosed by avian veterinarians and wildlife rehabilitators around the world. However, numerous other fungal infections occur in birds with less regularity or limited geographic distributions including trichomoniasis, fusariotoxicosis, aspergillosis, histoplasmosis, and clostridial dermatitis. Reducing exposure through cleaning protocols, ventilation, humidity control, stress reduction, and nutrition help manage fungal disease risks. But monitoring individual and population bird health is key to identifying any fungal issues early and pursuing rapid treatment guided by diagnostic testing. With an increasing environment of immune-suppressing diseases, global movement of species, and anthropogenic stressors, fungal infections in avian populations will likely continue posing conservation challenges for species survival and welfare for the foreseeable future.
